View Full Version : The TS-530/830 mod and upgrade thread
Many years ago I had an early model TS-830S; this the result of doing some home improvement work for a ham buddy. The radio and a TS-520S were sold to finance the purchase of my first street bike, at which time I drifted away from radio...for a little while.
The late 80s saw me acquire a TS-820S, then an R-820. An AT-230 followed soon thereafter. Over the years, that tuner was in and out of the shack a number of times. I'd often thought of selling it, but the desire to obtain the rest of the x30 line lingered in the back of my mind.
Fast forward to today. There are several of the rigs plus peripherals and a good sized box of spare boards and parts in my project queue. In this thread, we're going to have some fun modifying and upgrading them.
The 530 and 830 share common DNA, as I remarked in a Q&A thread elsewhere in the forum. The chassis, power transformer, power supplies, Final Amplifier assembly, RF Board (with a couple component omissions in the 530 series), PLL Board and Counter Board are for the most part interchangeable between the series. What's mostly different are the IF and AF Boards. The '830 is a dual conversion receiver scheme which uses an RF speech processor, while the '530's is a single conversion arrangement with an AF speech processor. The 830's SSB TX bandwidth is set by a different filter than the one used for reception, while the '530 series uses the same filter for both - albeit switching in a "Narrow" RX filter at the demand of the operator.
We're going to take advantage of both methods to broaden up the transmit audio a bit, enabling the radios to be on par with today's offerings. We're also going to fix the various IF Board gotchas common to each, improve reliability of the radios in general and add a few cool features - some of which Kenwood already gave us a head-start on. This thread will be updated and edited as I go; feel free to add to it.
References and parts sources:
KE5FTF - hybrid parts (mostly used)
https://kd7dny.com/shop/
http://www.somis.org/830.html
http://www.k4eaa.com/parts.htm
(http://www.k4eaa.com/parts.htm)
Tip #1: Better TX/RX filtering for the TS-530S
This one's pretty simple to do and offers improved TX audio quality as well as a more pleasant "Wide" SSB filter. The stock YK-88S (2.4KHz/6dB B/W) filter is swapped for a YK-88S-1 (2.7KHz/6dB B/W) unit. The filter can be scrounged from a number of rigs including the TS-830S, TS-940S and others which use an 8.83MHz IF.
As sourced, the rig included the YK-88C (500Hz/6dB B/W) CW filter. I added the YK-88SN (1.8KHz/6dB B/W) SSB filter and wired the Options jumper so that it's used as the CW-Wide filter (see photo):
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On-air tests with a station receiver using a Kenwood MC-50 were very gratifying. The '530 now sounds as nice as your typical EQ'ed ESSB rig, without exceeding permissible transmitted bandwidth.
Option: War Mode
Given the number of defunct sets and parts available in the marketplace, a dedicated individual could obtain a spare 530 IF Board and leave the stock SSB filter as-is, while fitting it with YK-88SN and YK-88CN (270Hz/6dB B/W) filters. If the set is to be pressed into contest use, the IF Boards can be swapped. This gives a little tighter, somewhat punchier SSB signal - which is desirable on a crowded band.
Other IF Board mods to follow.
Tip 2#: Don't reinvent the wheel, Part 1
The 830 series rigs offer two IF Outputs on their rear panel. One is designed to be used with an SM-220/BS-8 panadapter and the other is a narrow-band pre-product detector signal, for use in looking at a received signal's characteristics. Unfortunately, the 530 doesn't offer these...
Or does it?
I started comparing the IF Board and circuitry to that of the TS-830S (for the wideband output) and to the TS-820S (for the narrowband output). Remember that the TS-530 is a close cousin to the TS-820 in terms of conversion scheme and IF frequency. The '820 also offers IF Outputs for scope and panadapter, so some component re-use might be possible.
Turns out that things are a lot simpler in execution. To wit, the '820's product detector interstage coupling transformer is where the narrowband IF Out signal is taken from. Doing a little digging, one finds that the same transformer is used on the 530's IF Board.
It gets better. Looking at the area in question, one finds that Kenwood provided traces in the PCB which facilitate installation of the required parts. Here's the bare board:
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Here's the board with the required components (a .001uF disc capacitor at "C31" and a two-pin header) added:
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The header was obtained from a scrapped TS-930 Signal Board. Apparently, Taiko Denki produced the headers along with their mating plugs and the terminals used with them. Many rigs of the period use the connectors; Icom lists them in their Service Manuals as being TL-25 series. I'm planning to write T-D's headquarters and see if they're still available, or at least try to get a part number for the crimp terminals.
ETA:
Here's a picture of the terminal used in the plugs. They're 1.6mm wide across the triangle base.
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Rear-panel connector addition and cable fabrication is covered later in the thread.
W2NAP
06-11-2018, 01:05 PM
Invalid Attachment specified. If you followed a valid link, please notify the administrator (https://forums.hamisland.net/sendmessage.php)
Should be fixed. I noticed that hiccup earlier. :scratchchin:
Tip 3#: Don't reinvent the wheel, Part 2
Also needed is a wideband IF output for a panadapter - namely, the BS-8. If one studies the '830's IF Board schematic and parts list around the area of the Noise Blanker roofing filter then compares everything to the 530's, it's clearly evident that Kenwood left us some breadcrumbs. Namely, lands with empty, pre-drilled holes.
At least one "retrofit" floating around the Internet has the signal tap taken before the 1st IF Amplifier (Q1) at the RIF terminal of J1. Implement it the way Kenwood intended - just add the missing parts.
The ceramic NB filter has to be bent carefully away from the holes in order for the required 2-pin header to fit into the space, but as you can see it's quite doable - and follows the '830's schematic exactly.
Pic shows new header and 10K, 1/4w resistor to ground, across the IF Out pin. Note the orientation - we're following Kenwood's connector keying practice:
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The underside of the board, showing the new 47pF capacitor from the output side of L2 (ceramic filter input terminal) to the junction of the new header and 10k resistor. The two remaining empty holes had nothing in them to begin with:
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Wiring of the rear-panel jacks (using Kenwood parts) to be covered next.
Tip #4: Cosmetic improvements, Part 1
As shipped from Kenwood, the annunciator LEDs used above the VFO are all red. I wanted to give that area of the rig a little contrast, so I know at-a-glance what's going on with the various controls. This mod is applicable to all 530 and 830 models. (From left to right, the status LEDs indicate RF Attenuator On, Processor On, the rig's VFO is active and the Notch filter is on. This layout varies among models, and shown is that of a '530SP.)
LEDs used on the Readout board (immediately above the VFO assembly, and in front of the Counter module) are TLR-205. These are 1mmx5mm and are long since out of production...but they may be sourced from scrapped rigs (such as the FT-707's S Meter module) or the aftermarket. NTE 3161 (green) and 3162 (yellow) are direct replacements. I obtained the two yellow ones from one of my FT-980s, all of which are also getting the multicolor LED treatment - as their stock annunciators are yellow in color.
You'll need to remove the Counter module (several harnesses and four screws) to get at the Readout Board, then two screws remove it from the front panel. I used a green LED for the VFO indicator...and the OEM limiting resistor (R2, a 1.5k, 1/4w unit) made the LED a bit too dim for my tastes. Change this to around 1k while you have the board out.
The hardest part of the mod is getting the LEDs back into their front panel cutouts.
As far as the readout goes...nothing's faulty with your television. There's a gazillion wrong ways to add extra coverage to the x30 series rigs, and later on I'll cover the right way of doing it - via Counter module programming and use of the Aux band position.
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Wiring the IF Out
I wanted to re-use as much "Kenwood" as I could, given the availability of parts rigs and the components thereof. I also wanted to re-use the Kenwood style of construction, allowing for easy disassembly and module removal should servicing become necessary. An email to one of the parts sources listed in the first post got me a dual RCA plug from an '830, as well as a final compartment cover and the special transverter DIN jack (the addition of which will be detailed later in the thread).
As supplied, one of the leads was "just right" in length - but I had to scavenge another shielded cable plus terminals from part of a defunct '830 wiring harness, as the cable attached to the narrow-band output jack was about an inch too short. When constructing the new cable, I followed Kenwood's insulation convention for braid dressing. The installed jack assembly is shown here. OEM lead on the right; mine on the left:
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And the IF Board with the cables run to their headers. The cables were tie-wrapped into the harness at OEM points:
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W2NAP
06-12-2018, 07:53 PM
nice work
Tip #5: Improving transmit audio crispness
This one's taken from Rich Measures' (AG6K - SK) page, linked in the References section. The RF Bypass capacitor at the Mic Amp collector needs to be reduced, as the stock value also attenuates speech frequencies.
Applicable to both 530 and 830 series. Capacitor is identified as C53 in the 530 (adjacent to Q11) while it's C106 (adjacent to Q19) in the 830. Stock part is a .015uF mylar; I replaced it with a .0012uF of the same type and working voltage. I'll edit this section with a picture of the '830's circuit changes when I have one on the bench.
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KG4CGC
06-13-2018, 01:25 PM
:clap::clap::clap: WOW!
Tip #6: Product Detector upgrades
Also present on AG6K's "Circuit Improvements" page. Several modifications are made in this area. One involves swapping the OEM 1N60 diodes used in the product detector for low noise-figure Schottkys. The LO side of the bridge is unterminated; a resistor to ground fixes this. Next, a few components in the IF bypass RC network are changed - opening up the received bandwidth a bit, and as Rich noted "...you'll get the full effect of sky noise". The modification makes for a more robust sound from the speaker - and if less bandwidth is desired, the Narrow filters can be activated...or an accompanying SP-230 with its built-in audio filters can be used...or both.
Component changes on the '530's IF Board are as follows. These are applicable to the TS-830 as well, though depending on production run, not all parts may need to be swapped. The '830's component designators are different and will be covered in another post.
- R41 is changed from 6.8K to 2.7K
- C35 is changed from .033uF to .01uF. This is a polystyrene unit
- R42 is changed from 47K to 3.9-4.7K (I used 4.3K)
- D16-D19 are changed from 1N60 to 1N6263 or similar Schottky parts. I got a bunch of these from K4EAA and matched them to .001v forward drop before installation
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A 100 ohm, 1/4w resistor is added from the junction of R39 and R40 to ground:
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(Insert obligatory Linda Hamilton "...terminated..." quote here.)
Follow the service manual procedure and adjust the product detector via TC2. I used a scope and got the null down to the point that the LO energy was unobservable at the test point, the drain of Q4. I've tried using 1N5711s in my FT-90x projects and found the weak-signal performance to be a slight - but not a great - improvement. The 1N6263s seem to work better, at least in this application.
FWIW, I checked sensitivity with a signal generator at 14 and 28MHz. I cannot turn it down to the point that the signal isn't detectable (.01uV or thereabouts), and the recovered spectrum is very low in noise.
Tip #7: Balanced Modulator update
Another one borrowed from AG6K. The modification cleans up the transmitted signal a bit at the balanced modulator. In the 530, diodes D27-D30 (1N60) are changed to the same type as used in the previous modification. Follow the service manual procedure and null the carrier after the IF Board is reinstalled in the radio. The mod is applicable to the '830 too, albeit with different component identifiers.
I found it easier to do all IF Board mods at once, and in addition I replaced the large filter capacitors at the rear of the board with 450v, 105c-spec units while I had things apart.
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Tip #8: Fix TS-530 "S meter slam"
According to users, assorted 530 series rigs will slam their S meter's needle to the right on power-up. The meter in the rig on my bench was hitting its pin hard enough to be audible. Engaging the RF Attenuator, turning the AGC to Fast (or Off) and disconnecting the antenna can either reduce or eliminate the condition - if one remembers to do so.
User group comments reflect that the condition is 'normal' - although neither of my 830s do it. This prompted me to study the '830's AGC and S meter circuitry, and to attempt to identify a root cause.
A couple things become evident: The TS-530 series really IS a cost-reduced version of its big brother, as many key circuits are implemented in the same way but are lacking in a few areas. In the case of the '530's IF Board, a meter snubber circuit present in the '830 is missing. Then there's the matter of the AGC timing capacitor being installed backwards relative to that of the '830.
The fix involves pulling the IF Board, removing and re-installing C84, then adding a few components to the foil side. Easiest to do while you have the board out for other modifications:
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This is the "after" pic, with the capacitor installed as per the '830 ('+' terminal to the RF Gain control).
Next, add a 33uF 16-25WVDC capacitor and a series 1.5k 1/4w resistor from the 'M(eter)' line (pin 2 of connector 10) to ground. Circled is C84 - foil side - for reference.
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The orange tantalum capacitor next to the yellow circle is an addition. It's across R106 (10k) and connects to the (new) negative side of C84. Again, present in the '830. I used a 0.39uF 35WVDC part - though I may swap it for a 0.1-0.22uF some day (the latter value being used in the '830).
The S meter still pins on power-up, but with much less force - and somewhat less duration. AGC and ALC functions were checked and are not affected by the mod...only the action of the meter itself, and only from a cold start.
Further work may be done, at which time I'll edit the post as needed.
Adding a band to your 530/830 AUX position
As shipped, both series of rigs had provisions for adding an auxiliary band...according to Kenwood, for receive only. This band spot can also be made to transmit, and does not involve butchering the radio in any way.
What it does involve is a decent amount of resourcefulness, patience and a careful touch with the soldering iron. A well stocked junk box and test bench helps too - as does a well stocked beer cooler, for use with your friends whose junk boxes have all the required parts.
This isn't a so-called 'screwdriver' mod. Some component fabrication is required, as is removal of the RF Board and tinkering around the final amplifier assembly.
WARNING: VOLTAGES INSIDE WILL KILL YOUR ASS DEAD IF NOT CAREFUL. Bear in mind this ain't your grandfather's transistorized PA set.
I've chosen to add 27.0-27.5, as later on we'll look into how to make the '+0.5' switch work with it too. This will net us complete coverage from 27-30MHz, and will be useful in driving transverters whose IFs are at 27 or 28MHz. I'd refrain from adding 60M to the rigs - their VFOs run at 5.5-6MHz and there will possibly be an issue with reciprocal mixing products. Counter and PLL programming theory will be covered and is useful in adding other band ranges.
WARNING: USING THE COMPLETED RIG IN A SERVICE WHICH REQUIRES CERTIFICATED EQUIPMENT CAN PUT YOUR LICENSE IN JEOPARDY. EMERGENCY, RX OR TRANSVERTER USE ONLY, PLEASE.
There are several steps which are required to add a new band, and each will get its own section:
-Program the Counter Unit
-Remove the RF Unit and gain access to the PA compartment
-Wind coils
-Install coils (and on the '530's RF Board, add Transverter connection components)
-Configure the PA band switch
-Update PA compartment components as required
-Replace removed components and assemblies
-Align RF Unit and test
Program the Counter Unit
The x30 series rigs (including the TS-130) departed from previous Kenwoods in that they use a programmable PLL/VCO arrangement to derive the HFO - this instead of a design which uses a crystal controlled oscillator for each band segment; either directly or as a PLL reference. Both versions have their advantages, but the biggest one here is that adding a band range to the PLL merely requires a few switching diodes. The analog portion of the radio requires more work - which will be covered later in the thread.
It's worth mentioning one of the "hacks" which a person may run into when servicing a '530 or an '830. Kenwoods of this genre used a 4-bit BCD value to program the PLL for a given band range. Along the way, someone figured out that if you cut one of the logic lines going into the PLL Board, you can change the programming.
Yes, this buys you all of the 11M range (including the freeband areas above and below the Class D allocation). What it costs you is the use of 10M. Not the correct way to gain spectrum, especially if transverter use is the goal.
Shown here in an '830 is the requisite lead of J2 (PLL Board) after being cut to enable the mod; it was subsequently repaired by a former owner. Note that the frequency display DOES NOT TRACK with the actual frequency range if the mod is performed, as the counter readout is programmed independently of the PLL. Worth noting if you're restoring a rig which won't transceive where it's supposed to:
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Counter Unit theory and programming
There are two main functional areas which the Counter Unit is responsible for: Provide a readout of the actual operating frequency, by means of both preloaded band logic (for the three Most Significant Digits) and a circuit which counts the VFO output frequency and supplies it as a value for the three Least Significant Digits. Multiplexing of this information is handled by a single IC, and the band preload values for the readout are accomplished by diodes D105-D110 (absent) on the Counter Unit.
Similarly, the PLL Range Select programming is handled by diodes D101-D104 (also absent).
Note that 'absent' = logic HIGH (1). The circuit uses complementary programming, so we must install a diode to make a given line LOW (0).
One may study existing programming information in the Counter Unit and PLL sections of the '530/'830 Service Manuals to get an idea of how Kenwood implemented the various band ranges. For purposes of this thread, I've detailed a band with a start range of 27.0MHz.
You must first remove the Counter Unit from the radio (a number of wiring harnesses require unplugging) then take the shield off the assembly to gain access to the foil side of the board. Use a solder sucker to clean out the holes for D102, 106, 108 and 109 then insert and solder 1N4148 or similar silicon switching diodes, following the silkscreen mask for anode/cathode orientation:
15795
Use a pair of end cutting nippers to remove excess lead length then reassemble the Counter Unit and replace in the radio. Turn the set on and rotate the band switch to its Aux position, turn the Cal(ibrator) On and rotate the VFO to one of the marker frequencies. If everything was done properly, you'll hear the marker tone in the receiver (albeit weakly) and the displayed frequency will indicate the correct (new) band.
Remove the RF Unit
Arguably the most tedious part of the process. Given the fact I've removed the assembly a gazillion times while researching material for this thread, I can complete the task in about 10 minutes - assuming both top and bottom covers are already off the rig. Follow the process below and it's pretty easy:
- Be sure the rig is disconnected from mains power
- Unplug all harnesses from the Counter Unit and remove it from the rig
- Remove the Counter Unit bracket from the rig (2 screws)
- Remove the PA Compartment cover
- Use a shorting stick to short the top of the PA choke to a nearby ground
- Label the front-most PA tube then remove both tubes and set in a safe place
- Remove the PA Load knob and shaft (2 2mm set screws at front of flexible coupler)
- Remove the PA Tune shaft (loosen 4 screws on front coupler, front one on rear coupler, slide front coupler so as to permit shaft extraction)
- Loosen the Drive shaft coupler screws (4) then push the coupler as far forward as it will go
- Disconnect all header plugs and TMP plug (1) from the RF Unit. If unsure about where they go, take close-up photographs before removing them
- Remove band switch shaft tension springs (3) from the shaft. One is located between band switch wafers and the other two are attached to bulkheads
- Rotate the band switch to 1.5MHz. Locate the PA Tank bandswitch coupler (adjacent to front tube socket). Loosen both 2mm hex set screws
- Rotate the band switch to 10MHz. Loosen both 2mm set screws, then pull the bandswitch shaft all the way out. Avoid misaligning the wafers as you remove the shaft
- Remove 7 round-head sheet metal screws from the RF Unit
- Use an ~800 degrees F iron to remove the white wire that's soldered to the rear-most variable capacitor frame (530/830)
- De-solder the NFB wire from the PA Compartment feed-through insulator and remove (830 only)
- Stand the rig on its left side, locate the DRV wire at the rear right of the RF Unit (foil side) and de-solder (530/830)
- Lay the rig back down and lift the RF Unit out of the chassis. Remove the Driver tube and shield (optional). Set both rig and RF Unit aside.
Wind Ant/Mix and Drive coils - Part 1
There are several types of tuning coils used on the 530/830 RF Unit. Two are Toko shielded models, while the Driver coils are open-form, slug-tuned RF types for which I cannot find a modern-day equivalent - or source of surplus parts. Thus, we must dive into the junk box. Fortunately, the forms are the same type used on the TS-820's RF Unit...and there's no shortage of those boards in the Kenwood hybrid parts market.
I obtained the coil forms needed for the work in this thread - along with a lot of other useful parts - from a scrapped TS-930S Signal Board. Lodestone also has the forms (L30 series):
http://www.lodestonepacific.com/shieldedcoilform.php
Taking a look at the Ant/Mix coil area of the x30-series RF Unit, we see the following:
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The inductors for the new band will go in the areas circled yellow. The orange circled area is L12, one of the 10M inductors. I de-soldered the component for purposes of measuring its value.
A note about de-soldering: Don't attempt high volume component removal via heat and solder wick with any Kenwood hybrid's circuit board, else you'll end up lifting the foils from the board. They're made of phenolic material - not glass substrate, like Drake's and Cubic's gear of the day - and as such don't tolerate a lot of heat. Nor does the adhesive used thereon. At a minimum, buy a Hakko rework station which incorporates a temperature-controlled vacuum de-soldering handpiece. (Yes, I'm a Pace fanboy ... but Metcal, JBC, Etneo and the higher-end Weller rework stations are all good choices.)
Here's the 10M 'Ant(enna)' coil compared to one which fits into the Aux-band Ant/Mix spots. The difference is apparent:
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We cannot reuse the OEM 10M coil for purposes of this exercise, but we can re-use its value. Said value can be measured with an LCR meter, or a small capacitor can be tack-soldered across the coil and the tank then grid-dipped. We then approximate the required value and use the coil calculation info at
http://www.carnut.info/star-parts/pcbs/toko-winding.htm
although for this experiment we can use a value of 6 turns...derived empirically. Whatever gets us there. Bear in mind that for other band ranges, you'll have to calculate the required inductance - or measure the OEM coils used for a nearby ham band then determine the required inductance based on existing, known preselector-circuit tank values as a starting point.
Wind Ant/Mix and Drive coils - Part 2
Next, the Ant/Mix coils are wound. If you're using a new Toko or Lodestone form, the shield and ferri-cap will be separate from the coil tower and base pending assembly; you'll need to source some #40 magnet wire. If you're recycling a coil, it must be disassembled if the inductance is too high. The easiest way to do this is to use a small jeweler's screwdriver to gently lever out the indentations which lock the can to the base, by means of wedging the blade between the two. The tuning slug is then screwed flush with the top of the form and a small nut driver is used to push the form out of the shield. It takes patience and a bit of care.
Once everything is apart, unwind the "finish" side of the coil by de-soldering the winding from the base pin, then unwrapping it from the form. Leave the "start" side attached to the other pin:
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Wind a total of 6 turns starting in the second groove (3t) then skipping to the third (3t) then back down the center of the form to the pin which originally held the "finish" winding. Loop one turn around the pin then solder the wire to the pin. It'll take a few seconds for the insulation to burn away. A decent amount of flux helps, as does an iron temperature of ~700 degrees F:
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Take note of the 'center-tapped' comment. If the start winding point is on the side of the coil with no center pin, no big deal. Just remove the center pin with pliers and push it into the center hole in the other side of the form. It's only used as a locator in this application.
Use an ohmmeter across the coil to verify continuity between pins. Next, install the ferri-cap and shield can then check for shorts between coil pins and can. If everything checks out, set the completed coil aside and wind another just as you did the first.
Wind Ant/Mix and Drive coils - Part 3
The Drive coil for the new band is wound next. The form used is a 10mm base, "RF" style slug-tuned form. This type of coil was prevalent in a lot of '70s radio gear, particularly the CB and amateur offerings of the day. I managed to acquire several TS-820S RF Boards over the years and these became a donor source of coil forms for a number of similar projects - namely, adding 24.5MHz to the Aux spot of my 820 series rigs.
A word about the 10M coil and why it cannot be used "as-is" for purposes of this conversion. Compare it (#5570) to the 15M coil (#5560):
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As indicated, the 10M coil has a link winding. This is used to provide drive power for a transverter and is present on ALL 10M coils used in the Kenwood hybrids.
Problems will arise when you solder one of these into the Aux Drive Coil spot without removing the link winding. What happens is that it shorts the driver B+ to ground and takes out a 470-ohm metal-film resistor in the screen/driver plate power supply circuit. One can clip the offending wires at the pins and pull the link free - or one can use another coil as a starting point.
The band we're adding in this example needs more than 4 turns on its form to get a proper peak - but less than 5 - if the slug is to be centered in the form (as with the other Drive coils). Following the Ant/Mix/Drive alignment process in the '530's Service Manual, I could get a good peak with a 5-turn coil when the slug was about 2/3 out of the form. Less than optimal, but it works. Next, a 4-turn coil with a 4.5pF/1Kv NP0 ceramic disc capacitor installed at C103 (below) was tested:
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This resulted in a peak with the slug out 2/3 of the way from the form - same as the 5-turn coil with no capacitor installed. I believe the optimal combination in this case to be 4 turns (following Kenwood's winding pattern) with a 2pF, 1Kv NP0 at C103...but I used what I had in my parts bins.
Obviously, one will need to use different values for all these parts if putting the rig on some yet-to-be-granted band in the future (23 meters, anyone?) and the components used for the two nearest amateur bands can be used as a reference point for winding the coils.
RF Unit modifications and TS-530 Transverter connection
Next step is to install the new coils at L101, L102 and L103, along with the previously mentioned capacitor at C103. (I just got a bunch of 2pF, 500V silver mica caps and am going to try one with a 4-turn L103 next time I have an RF Unit out of one of the radios.)
There are a few more things to do to the board before reassembly can take place. One corrects an AGC overshoot condition and is detailed on AG6K's Circuit Improvements page. It's applicable to both 530 and 830 series rigs.
R12 (highlighted; near J4 and J5 at the lower left side of the board) is changed from 1 megohm to 10-51k, 1/4w. I used a 39k:
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Next, the components for the TS-530 Transverter Output signal are added. The Taiko Denki TL25-series header was salvaged from a junked TS-930 Signal Board, as were many other parts used in this project series. Skip this step if working with a TS-830 RF Unit, as the components are already installed:
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C38 (circled) is a 10pF, 100v NP0 ceramic disc capacitor and R8 (also circled) is an 82 ohm, 1/4w unit.
The last modification - assuming one wants the rig to transmit on the new band, and thus be useful in transverter service - is to locate R45, a 2.2K, 1/4w resistor which runs from J1, Pin 1 to Gnd. Clip or remove it. Better still, remove the resistor and install a 2-pin keyed header. This will be used to take "Aux Band" +9v to band-control logic which we'll build later.
R45 - if present - serves to limit output by means of the ALC circuit...but that's only one piece of the puzzle.
PA Compartment Mods and RF Unit replacement (530 and 830)
While the 6146s are removed, it's time to make some needed changes in the PA Compartment. All are indicated by colored arrows in the attachment.
1) Improved Bandswitch coupler - ordered from K4EAA, along with many other parts used for this project series. If the old (nylon) OEM unit is still in place, remove it and install the brass one in its place. Take note of the two flats on the PA Bandswitch shaft; the coupler goes on with its setscrews aligned with the flats. Don't tighten them just yet.
2) Replace the Plate Choke bypass capacitor - a .01uF, 3KV disc. So far, both rigs I've had on the bench for this thread have had cracked capacitors and I don't doubt the third will. These were also obtained from K4EAA in a "Final Compartment Repair Kit". Your junkbox will also work as a supply for this part - but mine was fresh out of anything with a working voltage above 1KV. Note: Remove the part before completing Step 3 then install the new component after. This gives more access to the switch contacts.
3) Add a connection to the 'Aux' Bandswitch position contact (indicated by the red arrow) - necessary for the unit to develop full rated power on a new band. For 25MHz and up, simply install a jumper between the Aux contact and the adjacent 28/29MHz contacts (which are themselves bridged). This is just doable with a very long tipped soldering iron, a set of very long electronics-sized needlenose pliers, a cuticle stick or similar wood tool (to position and hold a pre-formed jumper) and a long length of solder. For bands that require a tap to any other coil positions it's better to remove the PA Compartment as an assembly, where you can get access to the entire switch deck without fear of damaging anything.
Also advisable is the use of an iron whose tip can be temperature controlled. I used 800 degrees F to ensure rapid heating and proper fluxing of the joint.
15825
Once the PA Compartment updates are finished, reinstall the RF Unit. You'll position it in place then re-solder the two (530) or three (830) wires which were un-soldered to permit its extraction. Next, thread the Main Bandswitch Shaft through the front panel, into the various wafers (all of which should still line up with each other with respect to band contact wiper position) and then into the new PA Bandswitch Coupler. (Note that the Bandswitch Knob should be indicating '10MHz', and there should be a ~1/16" or so gap between the shaft skirt and the front panel.)
Center the coupler on the PA Bandswitch and Main Bandswitch shafts then gently snug up the first set of Allen screws (2mm hex driver). Next, rotate the Band knob to 1.8MHz and tighten the other two screws...then rotate the Band knob all the way to 'Aux' and back to 10MHz, ensuring that the knob skirt doesn't contact the front panel at any point of its travel. If all looks good, tighten the first two "snugged" screws then rotate the Band knob to 1.8MHz and verify the tightness of the second set of screws.
After the coupler is tightened, gently align the RF Unit to the chassis so its attachment holes line up with those in the radio's chassis. Replace 7 screws, noting that both long ones go into the holes equipped with standoff bushings. When this is done, rotate the Band knob though its range and ensure there's no binding. If everything checks out, replace the three tension springs you removed from the Main Bandswitch shaft during the disassembly process.
The rest of the assembly process is the reverse of the disassembly procedure - including the installation of all removed shafts, couplers and the Counter Unit. Alignment will be covered next. Note that with a '530 there's nothing to plug into the new "XV Out" connector (yet); the addition of the transverter interface and all supporting circuit changes will be covered elsewhere in the thread.
K7SGJ
07-11-2018, 12:22 PM
Fred, you have done a very professional job of documenting the Kenwood 530/830 mods and upgrades. The photos are very clear and help to make installation of these improvements very easy and minimize the chances of (as Grandma use to say) fuck ups. I have an entire 530 station that I purchased new many years ago. I also have the ancillary equipment like the panadapter, antenna tuner, monitor, mic, speaker, etc. In all the time I've had it, I have had to change tubes once, and replace something else that I don't recall what it was. I am at a point where I have to sell off a lot of my stuff, and sadly, that will have to go. It was my only rig for several years, and it has always been on the bench ready to go.
Anyway, nice job.
suddenseer
07-11-2018, 08:05 PM
As an engineer with fat, clumsy fingers I stayed away from that small, cramped Japanese mini compartment sleepers. Working around commercial broadcast gear maybe intended for people with bigis digitus. a cousin of a Roman solder. I am impressed. I need clamps, microscopes, with bright LED to solder them surface mount dust specks. Then a steady hand. I have not even tried to solder a PL 259 connector for some time. I have seen your component level work, you should teach a tech class.
More about coils and hardware hacking in general
Thanks Eddie and Tim for the vote of confidence...I'll try not to blow too many components up as I work through all this. :snicker:
One piece of lab equipment I have been missing for a while is an LCR meter. I got a used Leader LCR-745 from the 'Bay, and after repairing some damage caused by a piss-poor packing job on the part of the seller it was time to measure some of the components used for this project.
(Note: If you're going to make sub-microhenry inductance measurements in the course of tinkering, make sure you get an instrument which is capable of measuring components with an applied frequency of 10KHz or higher. The Leader unit uses 120Hz or 1KHz...just usable for a 1uH inductor. Another "Mods" thread will feature the design and construction of a range extender - if I don't bite the bullet and buy an HP 4200-series unit before then.)
In reply #18 of this thread, a link to a "Toko winding calculator" was given. I took the stock Kenwood 10M coil and measured it with the LCR-745 on 1KHz range, obtaining a value of 1.1uH. I next measured the 6-turn coil I wound on the 7mm form. Playing with the formula on that page:
uH = (AL x turns^2 )/1000
gives an AL value of 45 for an indicated inductance of 1.6uH. One could probably order a stock 1.2-1.7uH part from Lodestone and get it to work, or one could find a Toko engineer's design assortment of variable inductors and do same. Or bare forms can be ordered, and armed with the needed value and AL number a person can wind their own.
Alignment of the Aux Band
Once all components are back in places (including the tubes and the PA cover shield), it's time to align the new coils and test for power output. Rotate the Band selector to Aux, center the Drive control (12 o'clock) and turn the rig's VFO so that .250 is displayed on the readout. Turn the Calibrator on (or use an RF signal generator connected to the rig's ANT jack) and receive a signal of ~1KHz beat while in either LSB or USB. Peak L101 and L102 for maximum S meter indication. Do each several times, alternating between them. I can easily get .01uV minimum-signal sensitivity when connected to the generator and there's very little internal noise. Just what we want as an intermediate stage for VHF/UHF weak-signal work.
Next, follow the Drive Coil Adjustment procedure in the Service Manual to adjust L103 for maximum power out. Don't touch the Drive control while performing this step.
Finally, tune the rig up while on a dummy load and verify full output power can be obtained. Both the '530SP and '830S I've worked with will put out in excess of 100w, the former with a new set of tubes.
If you have a '530: Turn the rig off, unplug it and remove the PA cover shield. Then, short the Plate Choke to ground, remove the tubes and store them in a safe place. The addition of a transverter hookup is next.
Adding a Transverter interface to a TS-530S
Kenwood really did us a few favors here by using the same chassis, PA Assembly, Rectifier unit and ancillary circuits in both TS-830. and TS-530. All needed holes are present, and some minor rework to the existing boards is required. The major areas to focus on are the Rectifier Unit and the Antenna Relay, though a few other modifications must be done to the rig to make it the functional equivalent of an '830 when it comes to connecting a transverter.
In order of execution:
-Modify the RF Unit with the indicated parts (previously covered)
-Procure an OEM Kenwood TS-830 Transverter connector
-Disconnect the Screen Grid switch from its wiring
-Modify the AF Unit for Transverter ALC connection
-Modify the Rectifier Unit for relay control of screen voltage
-Rewire the Antenna Relay
-Wire the Screen Grid switch for the new control scheme and test the Screen Grid output terminal voltage
-Wire and install the Transverter connector
Walter (KD7DNY), a new Island member provided me with the connector, and KE5FTF sent a scrap wiring harness from which a few runs of miniature coax were sourced. The other parts were obtained from the scrapped TS-930 Signal Board or my junk box.
TS-530 Screen Grid switch, AF Unit modifications
The rear panel Screen Grid switch must be rewired to switch a +12VDC signal to the Rectifier Unit, following the TS-830's circuit. Easiest way to do this is to unscrew the unit from the chassis then trace each lead (two to the Rectifier Unit; one to the PA Unit PCB) and remove them from their attachment points. Next, de-solder the wires from the switch and set it aside.
Other than form factor and ancillary circuits, there's very little difference between the Audio Units of the TS-530 and TS-830 series. Examining the ALC portion of the assembly, the sole missing connection is the "XAL" (Transverter ALC) line. This is easily fixed. First, remove the AF Unit and locate J10 - a 2 pin TL25-series header. De-solder it and source a 3-pin version, then use a dental burr in a pin vise to drill a hole for the 3rd pin. Following Kenwood's connector positioning practice, install the header and solder two pins in place at the existing foil pads.
15838
Next, source a VO6B (1A; 600PRV) diode or 1N4000-series equivalent. An existing, non-drilled solder pad (indicated by the orange arrow in the picture below) was evidently meant to accommodate the needed diode but somewhere along the line the parts (along with the artwork for the connection to the header) weren't included. Trim the leads short and install as shown; cathode to the empty header pin:
15839
Lastly, source a 3-pin TL25-series plug and a suitable wire with installed crimp terminal. I followed Kenwood's color scheme and used a white/green striped wire - the one from this connector position in the '830. Remove the connectors one at a time from the 2-pin plug and install them in the 3-pin unit, keeping their positions the same. Finally, insert the terminal with the "XAL" lead into the plug, plug the connector into the header and route the XAL lead along the rear part of the chassis to the area where the Xverter connector will be installed.
15841
Install the AF Unit and connect any plugs which were removed.
ETA: See Tip #10 (post #39) for another AF Unit modification. I'd advise also doing this one while the board is out of the rig.
Modifying the TS-530 Rectifier Unit - Part 1
To accommodate a transverter, the Screen Grid voltage must be made negative - so the PA tubes will not amplify while the radio is in Transmit mode. In the TS-830 series, this is accomplished via a relay on the Rectifier Unit. Said relay is controlled by the rear-panel Screen Grid switch (by bringing one side of its coil to ground) or via an attached transverter (which brings a line on the Xverter connector to ground on power-up). The 530's Rectifier Unit is missing some key components; fortunately, these are easy to add. The PCBs are identical except for the part numbering.
Comparing the '830 Rectifier Unit schematic
15844
to that of the '530
15845
it becomes apparent that Kenwood cost-cut the latter while keeping the higher-voltage sections the same. Missing is the relay and its external control circuitry. Kenwood opted to run Screen Grid voltage directly through the 'SG' switch and reworked the area involving the -C, AC100 and SGS terminal. This is simple to reverse.
Modifying the TS-530 Rectifier Unit - Part 2
In the picture below, a stock Rectifier Unit is shown. Yellow arrows indicate components which must be removed:
15849
while red arrows show places where components must be added.
Begin by removing the Rectifier Unit from the radio chassis, then de-solder and remove the jumper and R17 (100k) which are inside the rectangular artwork area. Also clean out any solder from the pads which will be used to mount RL1.
Next, install D12 (1N4148, 1N914 or similar silicon switching diode), C7 (.01uF, 100WVDC ceramic disc) and RL1 (Omron G2E; 12V coil). The latter two parts were obtained from the junker TS-930S Signal Board and one can get several of the required relays from it.
Lastly, install a wire-wrap post at location "SGS". I used a pin from a Molex 'KK' series header (.156" C-C pin spacing) though one could be obtained from various junked Kenwood hybrid boards.
Note that R12-R13 along with wire-wrap post "STB" are not used in this transceiver...but they're present in the TS-830S, ostensibly to supply blocking voltage for the keying circuits.
The modified board is shown here; newly installed components indicated by yellow arrows:
15850
The orange wire on the "SGS" terminal will be installed later. Note the "12" terminal immediately underneath the "SGS" terminal. In the stock TS-530, this is used to connect screen grid voltage to the Mode switch. If the wire hasn't been previously removed in the Screen Grid Switch step (above), do so before proceeding. It will be attached elsewhere on the Rectifier Unit after testing.
Rewire the 530 Antenna relay
In the TS-530 series, the Antenna Relay's Receive (NC) contact is routed straight to the front-panel Attenuator control through a length of Miniax cable. The '830 intercepts this line at the X.VTER connector and provides a means to switch the RX input to an external signal source.
Shown is a portion of the '830 schematic. An additional run of Miniax (sourced from a discarded wiring harness, or from an electronic supply house) is added to the '530's Antenna relay after the existing connection at its NC (RX) terminal is de-soldered:
15851
Modifications to the socket connections of RL1 in the PA Compartment are shown. Once it's de-soldered, pull the line from the RF ATT connection out of the PA Compartment wiring and route it to the area between the EXT VFO and REMOTE connectors...where the new Xverter connector will be installed. Measure a length of Miniax to run between RL1 and the spot for the X.VTER connector - allowing an inch or two excess - then dress and prep the ends (braid and shield) per Kenwood practice. Connect center and shield to the points indicated on RL1's socket, then - following the original cable routing path - pull the Miniax through the chassis cutouts, along the rear wiring harness and to the X.VTER connector spot. Make sure none of the cables can come into contact with the final tubes or any moving parts (such as the band switch).
15852
The surplus harnesses I obtained had a couple of runs of exactly the right length.
Wire the Screen Grid switch
As previously noted, the TS-530 Screen Grid switch was wired directly into the Screen Grid supply. This component has been removed and the rest of the modifications to allow for remote switching of Screen Grid voltage will be covered.
A look at the '830 implementation is shown. In the "OFF" position, the "SGS" terminal on the Rectifier Unit is grounded - thereby allowing Rectifier Unit relay RL1 (not shown) to energize and supply a negative voltage to the PA tube screen grids. When the SG switch is set to "ON" (and the relay de-energized), positive voltage from the 210V supply is routed to the Rectifier Unit PD2 terminal, and from there to the screen grids of the PA tubes. Should an attached transverter bring Pin 4 of the X.VTER connector to ground, the relay will also energize, apply negative screen voltage and prevent the PA tubes from amplifying.
15860
Remove the wires currently on the Screen Grid switch and add a 12" length of yellow, orange and black solid-conductor #20 wire (salvaged from a junked wiring harness or supplied from your junk box) to the switch as shown:
15861
Kenwood's convention is to tie both poles of the switch together with these wires, so dress and solder them accordingly. Mount the switch so that the black wire is farthest away from the main power transformer. Next, route the black wire to the chassis ground nearest the main transformer...it has a pair of disc capacitors from the primary windings attached to it. Solder the wire to the ground point:
15862
Route the yellow wire along the back of the chassis and to the blank area where the X.VTER connector will be installed. Route the orange wire along the bundle which goes to the Rectifier Unit, trim and dress it then wire-wrap it to the "SGS" terminal (indicated by the orange and black arrow). I added a bit of solder to ensure a secure connection:
15863
Lastly, connect a wire from the "12" terminal (yellow and black arrow) to a source of +12v. I chose to route the wire to Pin 8 of the EXT VFO connector. In the TS-530 series there's a white/red stripe wire attached to this terminal, which is itself right next to switch "S21" - an integral part of the connector.
Check the "PD2" terminal output and wire the Screen Grid circuit
After all switch and Rectifier Unit modifications are complete and the assemblies fastened to the chassis, it's time to check the operation of the Screen Grid voltage supply. Ensure that the PA tube plate caps and suppressors cannot come in contact with any part of the chassis, then temporarily install the PA Compartment shield. Ensure that no loose wiring in the (future) X.VTER receptacle area can contact the chassis or other circuit components. Connect a DC voltmeter to the "PD2" pin (indicated by yellow arrow below), plug the rig into AC power and turn the Screen Grid (SG) and Power switches ON.
15869
In all modes besides TUNE, you should measure ~210VDC. Rotate the Mode switch to TUNE; the reading should be 100 to 110VDC. Next, turn the SG Switch OFF and observe the voltmeter: ~ -110VDC in all modes except TUNE and -50 to -65VDC while in TUNE.
If all checks out, turn the Power switch OFF then unplug the rig and allow the MV/HV supplies to bleed down. Short the "PD2" terminal to ground to ensure the filter capacitors have discharged. Obtain and connect a length of #18 solid conductor wire between terminal "PD2" on the Rectifier Unit and terminal "SG" on the PA Unit board. Kenwood's convention for this conductor in the TS-830 series was white w/ violet stripe; given that none of the scrap harnesses I had on-hand bore a suitable piece of that color scheme, I used what was available:
15870
Wire the '530's new X.VTER Connector
Reference the marked-up Service Manual screen shot and picture below for details on how to wire the connector. The one I attained surplus had the Miniax line to the RF Unit intact (including the TD plug), and the various wire jumpers (indicated on the screen shot) were also present. These will serve as a guide in making the rest of the connections.
The easiest way to wire the connector is to do so with it outside the chassis, with the exception of the wire which runs between Pin 2 and Pin 2 of the EXT VFO connector. Make all other connections first, attach the X.VTER connector to the rear bulkhead with its two small screws then make the Pin 2 - Pin 2 connection.
15874
15875
Once everything is secure, test the receiver function - making sure that the RX signal path (now run through the X.VTER switch) is complete and allows HF reception when no plug is inserted in the X.VTER connector.
The TS-830S User Manual has details of the function of each X.VTER connector pin...but the "X-verter ON-OFF control" description is a bit vague. Bringing this line to ground (when powering up an attached transverter, as an example) will activate RL1 on the Rectifier Unit, thereby removing Screen Grid voltage from the PA tubes. The Driver tube will still provide 10M drive energy, but the rig's PA won't amplify.
Note: There is no filtering on the "Transverter Output" line - either in the stock '830 or the modified '530. It's strongly suggested that a suitable low-pass filter be constructed and placed somewhere between RF Unit J10 and the transverter drive input point.
Assuming all checks out...unplug the rig, discharge the plate choke then replace the PA tubes in their sockets and attach their plate caps. Other PA circuit mods and neutralization plus balanced modulator adjustment to follow.
KD8TUT
08-13-2018, 07:05 PM
Thanks for posting this... it's a great read.
Thanks for posting this... it's a great read.
Lots more to come!
I got word from the Kenwood Hybrids Reflector that Ken (K4EAA) has some health problems, and his wife Barb and son are filling parts orders as they get them. They thank everyone for the continuing patronage. I'm going to order more shaft couplers and 1N6263s in the next few days.
Tip #9 - PA Tube longevity, performance improvements
Another bit from the AG6K 'Circuit Improvements' page. Rationale is that the 6146s are being run at a slightly high filament voltage, and over time the (overheated) cathodes lose their barium coating...which sticks to the screen grids and causes secondary emissions when a load is put on the tubes. This has the effect of reducing power output as the key is held down.
The fix is simple. A pack of 3-position, end-lug terminal strips were obtained from an online vendor - as were several 0.51 ohm, 2w metal film resistors. The mounting lug was flattened and this allows the strip to be attached to one of the existing Final Unit mounting screws. The resistor was then mounted in the two lug-attachment crimp holes after having its leads bent for adequate clearance.
Kenwood ran a wire from the Heater switch to the "H" terminal of the Final Unit, and a wire which supplies filament voltage to the RF Unit's Driver Tube is also connected to this point. Both were removed and attached to the input side of the resistor. Next, a bit of the solder mask surrounding the "H" pin was scraped away and extra solder flowed onto the area - giving additional mechanical support for the pin. A wire is run from this pin and attached to the output side of the resistor, and the strip then fastened into place using the existing screw. The yellow/white 'IPM' (metering) wire was routed to clear the resistor:
15891
I left the Driver Tube filament power as-is and installed new PA tubes plus a new Driver Tube in the course of this project. Although long key-down operations aren't anticipated (except in the case of the AM conversions which will follow), the Driver Tube performance will be monitored over time and the filament power wire re-routed if needed. One of the other rigs I'm working with will have its Driver Tube filament power dropped through the resistor as a control test.
A note about the asterisk: Always tidy up after yourself. In the case of these modifications, you're going to do a lot of tie-wrap cutting to get at various conductors in the stock wiring harnesses...and you'll need to add new wires into the bundles. Those harnesses need securing - via ties - when done. The correct (OEM) size is a 1.8mm wide tie; most commonly available ones are 2.5mm or larger. An eBay store had a 1000-ct bag of Huada brand 1.8x60mm ties for $10 - more than enough to do every hybrid in one's collection. A new tie is shown in the picture, after the new 'XAL' wire from the AF Unit joined the bundle.
Tool Tip #1
At some point in time, Kenwood went with an Antenna Connector retention nut which is a pin - rather than a hex - type. This is the same style of nut used on practically every 8-pin microphone connector in existence. Unable to find a suitable OEM tool several years ago, I built one for purposes of taking microphone jacks out of front panels or tightening them up after repairs are complete. Luckily, the improvised tool works great for the random, loose Kenwood Antenna Connector nut.
Start by taking the brass retaining shell off a junk PL-259 connector assembly. Use a machinist's combination square w/ center head or similar measuring device to make 4 marks at 90 degree intervals on the non-threaded end. Secure the threaded end in a vise then use a flat-edged file to remove material from between the marks to a depth of 3/32" or so....occasionally test-fitting with a nut as you go. For finish work, use a flat rectangular needle file to square and neaten everything up. You want the pins to be loose in the nut engagement slots, but not overly so.
15892
Engaged in the Antenna Connector nut of the project TS-530SP:
15893
If anyone reading this knows of a commercially available tool, PM me with details and I'll add them to the thread.
Tip #10 - Improve the TS-530 power supply filtering
This one's so simple it leaves a person scratching their head as to why it wasn't implemented from the factory. In the TS-830S, a Pi (capacitor-choke) filter is used on the input of the 12V regulator circuit, which is shown here:
15894
For comparison purposes, the TS-530 schematic. I was tipped off to the omission via a discussion on another ham radio forum:
15895
Note "J36". There's a spot on the AF Unit board for the choke, but the bean counters evidently decided their "Cents-ational!" member of the x30 line didn't need it...so a wire jumper was used instead.
Looking at the AF Unit, one sees the space for the choke - and the jumper used in its place:
15896
I decided to do some investigation and see if the part was actually required. A scope was attached to the AF Unit "12" pin (12V output), set to AC coupling and the rig powered on. What was observed was a veritable cornucopia of noise and ripple, some of it reaching into the HF spectrum and exceeding 100mV in amplitude. One wonders if the condition was caught during the rig's QA or engineering eval phases...
The choke used in the '830 line (and a number of other Kenwood rigs) in P/N L15-0016-05. No data appears about this part online, though it's available to order from PacParts. I dug into my junk box and found a few chokes of the same form factor; these had been salvaged from CB sets over the years. Using the LCR bridge with a 120Hz test signal, I inspected the lot. Of them, I selected an 8mHy part; it had a measured Q of 3.6. The windings look to be good for 2-3A, which jives with an SSB CB's power requirements.
The AF Unit was removed from the rig, J36 was removed, the solder pads cleaned and the choke installed:
15897
Repeating the test with the scope showed ALL higher-frequency garbage gone, and the residual (AF) superimposed ripple on the 12V line was <10mV at full audio output. As a bonus, receiver noise dropped by at least an S-unit...though sensitivity didn't change.
Afterwards, the 9V and 3.2V regulated supplies were checked and set. I let the radio run for an extended period of time in its normal (right-side-up) position and periodically checked the choke temperature. It never increased to a level higher than "rig ambient".
General '530 Alignment notes, tips
Once everything is back in place and all wires are secured it's time to perform an alignment of the RF Unit and Final Unit (PA tube neutralizing) and check carrier suppression. The Driver Tube is an integral part of the RF Unit's tuned circuits, and the Ant/Mix and Drive coils for all bands should be re-peaked whenever the tube is changed - especially between brands.
Following the Kenwood Service Manual, I did the neutralization procedure first. Afterwards, the RF Unit coils were adjusted in sequence. That is, the Ant/Mix coils for a given band were peaked (using the internal Calibrator output as a signal source) followed by the Drive coil adjustment. One uses an external wattmeter for this procedure, tuning the Plate and Load control for max indication then peaking the band's Drive coil. The Mode switch is kept in Tune for the procedure, and (very important!) the Drive control is kept at 12 o'clock throughout.
Once the RF Unit adjustment is complete, tune the rig up on 14MHz (per the Service Manual), remove the dummy load and connect a 15MHz B/W or higher oscilloscope to the Antenna Connector. With the Mode switch in either USB or LSB and the Mic Gain fully CCW, flip the Send/Rec switch to Send and alternatively adjust TC1 and VR4 for minimum carrier on the scope. Select the opposite sideband and check the carrier level, adjusting TC1 and VR4 to equalize the readings between sidebands.
With the new (1N6263) diodes in place in the balanced modulator, I was able to get the carrier level down into the noise on both sidebands - 3-4mV max.
Depending on condition and past ownership, a full alignment of the rig may be in order. Follow the Service Manual procedure throughout, starting with the 9V and 3.2V regulator adjustments. The former determines overall VFO stability. I've seen the x30-series rigs take a bad rap for drift, but the one currently on my bench has stayed put after warmup.
Tips #11 and 12 - fill those unsightly "Aux Connector" rear-panel holes
Kenwood provided a couple of empty holes on the 530 and 830 rear panel - per their manual, for Auxiliary I/O connectors. One documented use is for a phone patch input (also usable for AFSK). Another is for a phone patch output or demodulator connection...still others are for IF outputs to a band or signal scope. Since we added the scope I/O to the '530 via a TS-830S I/O sub-panel, we can now use the holes for custom I/O applications. (Connector additions to a TS-830 will be covered later in the thread.)
Covered here will be a Phone Patch input and a Sidetone output; the latter is useful when running the transceiver with a secondary receiver.
Sidetone Output connections - TS-530
This is fairly simple to implement but requires removal of the AF Unit from the underside of the chassis. Existing test point 'TP1' and a nearby (empty) ground connection are used.
The stock AF Unit, with TP1 (a large square terminal) installed:
15908
The foil side:
15909
De-solder the TP1 post, clear out the TPG hole then source two 0.025" (.63mm) square posts. A header such as those found on the TS-930S Signal Board - or any similar part - will provide the needed posts. Solder them into place, then install the AF Unit:
15910
Get a length of Miniax suitable to span between the AF Unit and the rear panel, via being routed from bottom to top of the rig. I used the speaker connection wire from an '830 and de-soldered the 2P plug from one end. Two Molex 16-02-0102-C connectors were attached to the center and shield wires, then heat shrink was applied:
15911
Attach the center and ground wires to TP1 and TPG, respectively:
15912
Route the new cable to the top side of the chassis via the cutout nearest the AF Unit. Dress the lead along the existing IF Unit bundle and to the rear of the chassis, where it will be connected later.
KG4CGC
08-28-2018, 01:06 PM
Your work and understanding is beyond the grasp of what is expected today.
PA5COR
08-29-2018, 04:29 PM
Loved reading it, stellar job....:bowdown:
Phone Patch input connections - TS-530
Those who wish to run audio signals from a patch, data communications terminal or other device straight to the Mic Amp (instead of using the rig's Mic jack) will find this modification useful. The electrical implementation is fairly simple. The mechanical implementation is another matter entirely.
The best way to perform the mod is to de-solder J14 and fit an 8-pin header of the same (Taiko Denki TL-25) series. The TS-930S Signal Board is a good source for these. A circuit board mod consisting of drilling a small hole between two existing ones immediately to the left of J14 is required:
15918
Use a small Dremel ball mill to remove the ground foil in the area surrounding the new pin.
Next, modify the 8-pin header by removing the 4th pin from the left and installing it into the holes. You may have to use a solder removal tool to clean out the existing holes either side of the new one.
Note 1: The holes for J14 and the two others immediately to the left of it may not line up perfectly from one board to the next (I have several) but the 8-pin connector can be fit into place.
Note 2: There are a couple of ways to proceed when it comes to attaching a connector to the 'new' J14. One is to source an 8-pin plug and move the existing P14 wires to their respective positions, then add the new leads to the left side of the plug. The other (which is shown here) involves filing a slot in the back of the header barrier so the existing P14 (a 4-pin plug) and a new 3-pin plug can fit side by side. The new 3-pin plug takes a pair of T-D terminals attached to a length of Miniax...left is shield; middle is center conductor. I re-used a 6" length (complete with terminals) from a junked x30 wiring harness.
The modified 'J14':
15919
Also shown is a replacement relay for RL1; this available from K4EAA. I swapped it for the stock one in an effort to see if the S-meter "slam" condition would be affected. No dice, but no worse.
Make the Phone Patch input connection from 'J14' to the junction of C50, C51 and R61 with a 100K, 1/4w film resistor. The schematic attachment point:
15920
And the underside of the IF Unit is shown here:
15921
Note the 10K, 1/4w film resistor which bypasses the input connector to ground. The patch connection is per Kenwood's TS-830S modification info, and the Mic Amp circuits are identical between radio series.
Check your work for solder bridges and replace the IF Unit in the radio. Rear panel connector installation is next.
Rear panel connector wiring - both models
Install a pair of 3501FP or equivalent RCA jacks in the two empty holes near the IF Output jacks, then wire the Sidetone Out (bottom) and Phone Patch In (top) connections. Use a few of the 1.8mm tie wraps to include the new Miniax runs in the existing cable bundles.
15922
Note that the Sidetone Out line is at full oscillator volume. A pad may be added at the external receiver (or built into the patch cable itself) to set the level heard from the receiver's speaker.
Tip #13: Cosmetic improvements, Part 2
Applicable to VFO-230 users. The Status LEDs are changed (per Tip #4) to yellow and green variants. Seeing what the rig and external VFO are doing in regards to frequency control is MUCH easier with this modification, especially when operating in a dimly lit room.
The VFO-230's top cover must come off, then the RIT knob, main tuning knob and memory selector knob are all removed. Three screws - two on the side of, and one on the bottom of the bottom cover - retain the front panel. Remove these, pull the panel off the VFO-230 and set it aside for safekeeping. The LED circuit board can then be accessed. I found that by experimenting with installed LED height (depth into the front panel), the brightness can be adjusted somewhat without changing the dropping resistors (as was done in Tip #4). Leave the front panel loose until satisfied with the appearance then reassemble the front panel and top cover and reinstall the knobs.
15923
Tip #14: Cosmetic improvements, Part 3
A lot of these rigs have received their share of scratches, dings and scrapes over the years - most on the covers and on the outside edges of the front panel. An eBay seller routinely offers light and dark "Kenwood Hybrid" paint for purposes of restoration.
The covers are an easy proposition: Remove all hardware, scuff the existing finish with 400 grit emery cloth, wipe with isopropyl alcohol then re-paint after thoroughly dry. (If any rust is present, use a Dremel tool and brass wire wheel to remove it and any nearby paint before scuffing.) Wait for the paint to air dry then bake the covers for a couple of hours at 170 degrees F.
A couple schools of thought on the front panel and repairs to the edges: If the covers are off the rig, the 'mask and wipe' method can be used to fill in scratches and light gouges. That is...put masking tape about 1/8 - 1/4" from either side of the scratch and along the front of the rig. Spray a bit of the dark paint into a shallow, clean plastic cup then use a cotton ball or non-fibrous rag to wipe a bit of paint along the scratch, from front to back. Repeat a few times as the applied paint dries, then remove the tape. Let dry completely for several days then use #1500 wet sandpaper to very gently blend the patch in with the rest of the panel.
This resulted in a 6-inch job on my TS-530SP's front panel. That is, you have to be within 6 inches of the repair to identify it - due to a bit of the original primer bleeding through. You couldn't tell it in a close-up photo but I know it's there.
The best way to fix paint damage to the edges of the front panel is to remove it completely from the radio, mask the entire front (so no overspray can leak through)then lightly scuff the edges with 600 grit emery, wipe with alcohol and spray with a couple coats of the color-matched paint. Most of these rigs have a 3D "ledge" around the panel near the outer edge surface and one may use that as a masking guide. Try to spray the paint towards the back of the edge and avoid building up a fillet of paint near the tape interface.
When dry, remove the tape and bake as you did the covers. I'd follow this step with a coat of Collinite #845 ('Insulator Wax') before putting the panel back on the radio.
Thread bump:
I finally got around to putting the '530SP, VFO-230, AT-230 and two SP-230s into the 10M operating position over the holidays. The rightmost operating position now has a TS-930S/SP-930/SM-220; given that the '930 has no provision for a wideband IF Out, I decided to connect the SM-220's panadapter input to the modded '530SP.
All the mods I did to this rig work swimmingly. An area friend/infrequent Island participant recorded me on his Flex 6700 and played the audio back over the air. Mic is a stock MC-50, with no EQ inline or other audio modifications save the ones in this thread. The radio's transmitted audio is friggin' GREAT. The speech processor (audio based) merely increases the power level - relative to the Mic Gain setting -and doesn't alter the transmitted signal's characteristics. In other words...it doesn't sound "processed" but intelligibility definitely goes up.
The auxiliary I/O connections function as they do on the '830 series. Not surprising, as 99% of the required circuitry was already there.
Next in line is the conversion of an '830S to an '830M.
KA2PTE
11-14-2020, 11:04 AM
Hope its ok to add to this spectacular thread.
My 530S already had this done, I guess it would work for any hybrid of the same design. It makes neutralizing the finals possible without taking
anything apart. I measure the distances about 65-66mm from the side of the bottom case cover, and about 123mm from the closest part of the back part of the cover.
The hole is about 0.312 inches / 7.93mm. I think they used a quarter inch drill bit then reamed it to be a little over 5/16 an inch as its not perfectly centered. You can get a non metalic flat blade in there and hit the adjuster, so it does work.
17296
UPDATE: Since I had the bottom cover off anyhow, I measured from the ends of the frame of the chassis to the center of TC1. The measurements are more like 64mm and 121mm to be more precise.
Hope its ok to add to this spectacular thread.
By all means. Everyone doing work on one of these rigs should document and post the results here.
KA2PTE
12-29-2020, 06:24 PM
I pulled an L5 from a spare AF-AVR PCB that went to a TS-830S. It measures 2.87mH on my tester
and its got this number stamped on the metal band: L15-0016-05. Searching online for that term reveals its used in
some other later Kenwood riggs. It does not look burnt or overloaded, so installed it into my 530S's PCB. Have not powered up yet
but I am guessing it will be fine.
Tip #10 - Improve the TS-530 power supply filtering
The choke used in the '830 line (and a number of other Kenwood rigs) in P/N L15-0016-05. No data appears about this part online, though it's available to order from PacParts. I dug into my junk box and found a few chokes of the same form factor; these had been salvaged from CB sets over the years. Using the LCR bridge with a 120Hz test signal, I inspected the lot. Of them, I selected an 8mHy part; it had a measured Q of 3.6. The windings look to be good for 2-3A, which jives with an SSB CB's power requirements.
KA2PTE
12-31-2020, 03:54 PM
Tip #6: Product Detector upgrades
- R41 is changed from 6.8K to 2.7K
- C35 is changed from .033uF to .01uF. This is a polystyrene unit
- R42 is changed from 47K to 3.9-4.7K (I used 4.3K)
- D16-D19 are changed from 1N60 to 1N6263 or similar Schottky parts. I got a bunch of these from K4EAA and matched them to .001v forward drop before installation
A 100 ohm, 1/4w resistor is added from the junction of R39 and R40 to ground:
Ok decided to try this mod on my 830S. It seems to me the area on its schematic is near D20-D23, which are all 1N60 type diodes. I have taken a photo showing them on the pcb.
17361
R42 in the 530 seems to be R78 and R41 is R77, but its already been changed to 2.7K in the 830S.
C63 in the 830 appears to be the same component as C35 but its been lowered to 0.022.
Not sure if I ought to change them to match, and from what I can tell R75 and R76 are the equivalent to R39 and R40
and when you follow the connect trail, there's no termination resistor I can see.
UPDATE: I terminated the product detector via R75 and R76 to ground with the 100 ohm resistor, put everything back together for a listen.
It does sound improved on rx somewhat and I am told audios good so I guess it was a success.
This is a photo of the 100 ohm resistor terminating on the foil side:
17363
Excellent.
I'll keep the thread hijacks/hijinks to a minimum but I strongly suspect my NRD-515 receivers can benefit from this mod as well - and by having their AGC detector diodes swapped for a properly biased Schottky part.
Back to our regularly scheduled Kenwood goodness. I'm going to drag my '830S out of its shipping box in the near future and start doing some upgrades to it.
KA2PTE
01-01-2021, 01:02 PM
Interesting, because I noted there are lots of other 1N60 diodes in these Hybrids, but not sure of their circuit function. The 1N60 is a basic germanium diode it seems.
Excellent.
I'll keep the thread hijacks/hijinks to a minimum but I strongly suspect my NRD-515 receivers can benefit from this mod as well - and by having their AGC detector diodes swapped for a properly biased Schottky part.
Back to our regularly scheduled Kenwood goodness. I'm going to drag my '830S out of its shipping box in the near future and start doing some upgrades to it.
KA2PTE
01-01-2021, 01:37 PM
As per AG6K's page on somis.org :
Rapid jumps in VFO frequency. Cause(s): [1] This can be caused by fluctuation in the 9V regulated power-supply voltage, which is the result of an intermittent connection between the AF-AVR [automatic voltage-regulator] Unit's circuit-common and chassis ground. Fix(s): [1] Solder a wire to the "TPG" terminal, next to C81, on the AF-AVR Unit. On the other end of this wire, solder a #6 ground-lug with locking teeth. The ground-lug is placed under one of the nearby sheet-metal-screws that fastens the AF-AVR Unit to the chassis.
An alternate method, if you are already doing other work on the board is to merely scrape off the coating at (2) locations
on the foil side and make solder jumpers. This will effectively bring the floating ground condition permanently to a
hard wired ground coming in on the +40V line for the power transistors. That way if over time the screw loosens, its irrelevant. This photo shows the procedure, works on both AVR boards in either radio.
17364
KA2PTE
01-01-2021, 05:44 PM
The OMRON branded relay on the 530s's IF pcb, the same kind used on the 830's AVR board is a well documented point of failure in both radios mostly for rx issues. There is a solution for the obsolete relay out there on K4EAA's site, however I chose to carefully and painstakingly clean my relay contacts in both radios with a nail file and compressed air. It took 2 attempts but I got the relays working again and so far for many months, there's no issues. Of course I dont do much CW, but I imagine during CW operation, these relays take a pounding and that could be why they are prone to faults.
Also, its well known that the coils on any relay will produce a high voltage counter_emf every time voltage is removed. Snubber diodes are usually placed on the coils to absorb the voltage so its not applied to the circuit design. However over time snubber diodes will get tired and develop hard to spot breakdowns of the junction reverse bias which could cause the relays open and close time to be effected. While I was working on my AVR board, I decided to change D10, the snubber as a maintenance item. I upgraded it to a new motorola 1N4003 series diode I had in my parts bin. While the original 1S1555 diode is lower current and faster switching, the 4000 series diode will take more abuse, so I tend to like this approach. The only drawback may be the 4000 series is rated at a slower reverse switch time then what its replacing, but I dont think its great enough than the actual open and close time for the contact, unless someone hooks up a cw bug and tries 100wpm code.
I took photos showing D10 on the 530S's AVR board, before and after the swap.
Before 17365 After 17366
On the 830S, the Diode is D27 and is right next to the OMRON relay in plain view. Apparently they moved the relay from the IF board to the AVR board in the 830S.
17367
In the past I have seen relays in other gear fail due to the snubber actually reading like a resistor after many cycles. This could be because the diode itself was cheaply or poorly made or the counter EMF somehow exceeded the diodes rating.
KA2PTE
07-25-2022, 11:18 AM
I wound up with another 530S and am giving it a going over with these procedures. So far so good.
Wanted to make a note that I got bit with the plate voltage that goes to the driver tube when I touched
the rear bandswitch wafer. Turns out on the rectifier board, R9 (330K) was completely open, its the bleeder
resistor for that supply and its a common fail in many of these, so if you are going into this board, check or replace.
Also the (2) 56K half watt resistors on the board forming a voltage divider also drift pretty far out of tolerance and
ought to be replaced.
[QUOTE=N8YX;665620]Modifying the TS-530 Rectifier Unit - Part 2
15849
g1cpu
03-11-2024, 07:25 AM
I am writing to thank you guys for documenting these improvements. I stumbled on this article and then this forum yesterday. I am in the middle of breathing life back in to a TS-530, two TS-830S's and a TS-830M (as shown on my qrz page). The photographs say a thousand words and help me confidently to look where the action is. Although this article was last updated a couple of years ago, those like myself still find snippets of well documented suggestions like this very valuable. Thanks. Greg G1CPU
I am writing to thank you guys for documenting these improvements. I stumbled on this article and then this forum yesterday. I am in the middle of breathing life back in to a TS-530, two TS-830S's and a TS-830M (as shown on my qrz page). The photographs say a thousand words and help me confidently to look where the action is. Although this article was last updated a couple of years ago, those like myself still find snippets of well documented suggestions like this very valuable. Thanks. Greg G1CPU
Greg,
Quite welcome. As I'd indicated earlier in thread I have a project -S that I'm going to convert to an -M and redesign the AM TX side of things in the process to get away from the (in)famous sideband+carrier approach that Kenwood so loves.
Be sure to post pics or details of what you run into with yours as you go.
Using the "+0.5" switch with the Aux Band
Do not adjust your monitor (or your TV). What you're seeing is real (though it wasn't real fun going cross eyed studying the '830 Service Manual for several hours on end).
This is a proof-of-concept shot of the Aux Band-expanded TS-530SP - the guinea pig for the mod series I've documented - receiving my signal generator on the indicated frequency. It's 500KHz up from the "base" allocation we added on Page 2. I'll follow with a several shots out of the manual describing how this works, what needs to be added to the Counter Unit to get the indicated range...then lastly, how to use the +500KHz panel switch to select the additional range as is done with 28 and 29MHz. What we'll end up with is complete coverage from 27-30MHz - useful for the oddball transverter IF. As stated before, don't jeopardize your license by using non-certificated gear on a band which requires it. Listening is fine. Keeping the Heater switch off keeps one honest. :yes:
18239
In Post 16 of the thread I touched on programming the Counter Unit (which also controls the PLL Unit). As mentioned before, this is done by a diode matrix - both as-delivered from Kenwood and by the end user who wishes to add an extra band. Snipped from the Service Manual is a pic of the Counter Unit schematic with the matrix and preload areas.
18241
Q5 is the counter chip. It's programmed in BCD and the various diodes plus Q8 and Q9 serve to put frequency-start information on its preload inputs. Q14 is the PLL Preload output and serves to place BCD information on the PLL control bus.
All of the values are determined by that diode matrix and a bit of theory behind the circuit is contained in the Service Manual. Note that the same Counter and PLL Units are used across the 530/830 series so this information applies universally.
Post 16 covered adding the required diodes for our test range. Next, we'll dive deeper into "why".
First, the Counter Programming table. Not all possible ranges are described in it, but enough for the user to understand how the counter operates.
18243
The astute reader will notice that each indicated segment is 500KHz lower than the start of the band edge it represents. This is due to the VFO frequency being summed with the counter preload values. For a given range to indicate properly, the preload value must be set correctly (via diodes D105-D110). These set the 20/10MHz digits, the MHz digits and the 500KHz starting point (for bands starting with a ".000" MHz value).
Look at the D-C-B-A values, starting at 29.5 and progressing downwards. Notice how they increment by 1. Also notice a couple possible values below 28.
Next, the PLL Preload information.
18245
As in the post above, look at the D-C-B-A values...and spot a couple of curious possibilities below 28.
Doing a little binary math, we come up with the following permutations and the ranges they enable:
D C B A
Counter Start
Covered Range
1 1 0 1
27.0
27.5 - 28.0
1 1 0 0
26.5
27.0 - 27.5
Either one is easy to implement by itself. Post 16 covered the addition of D102, D106, D108 and D109 to the Counter Unit to successfully obtain 27.0-27.5. A project earlier in the week was re-analysis of the circuit logic and determining what else would be required to get the unit to shift the Aux band up 500KHz, thus covering 27.5-28.0. Turns out that the addition of two diodes is it. These are D101 and D107, arrowed in the pic shown here:
18247
So what if we want both ranges, like we get with 28 and 29MHz via the "+0.5" push button switch? Turns out real life ain't so simple.
Have a look at the Counter and PLL interconnects, from the main schematic. Examine S7 at the bottom of the picture. Note the "28" and "29" lines.
18249
And the related Band Switch area:
18251
The 28 and 29 lines are energized with +9v when the Band selector is on either of those bands. What happens on the Counter Unit is that the switch (an Alps DPDT latching type) is used to send control voltages to two distinct diode groups per band. One for the standard allocation and the next, 500KHz higher. Refer to the Counter schematic (earlier on page) for details of the control logic used for the 28-28.5-29-29.5 bands.
Using the front-panel switch
What's sorely needed is a third switch pole, to handle the Aux Band control switching independently of the other two. I literally spent hours online last night trying to find one (or a 4PDT version) of that OEM Kenwood part. But there isn't any such animal. Next thoughts were to use a 4PDT relay to switch the control lines independently. That would entail a lot of extra wiring and the potential of the relay going bad at some point.
What if we could re-use some of the existing diode matrix to control the preload data?
D C B A
Counter Start
Covered Range
1 1 0 1
27.0
27.5 - 28.0
1 1 0 0
26.5
27.0 - 27.5
1 0 0 1
28.5
29.0 - 29.5
1 0 0 0
29.0
29.5 - 30.0
Laid out like this, we readily see the commonalities. The only difference between 27 and 29MHz coverage is that the "C" line is being set.
Going back through the Counter circuit and tracing every signal path through the diode matrix when the 27.5MHz band is programmed, one comes up with the following required deltas. Diodes indicates by red arrows are additions from the original information in Post #16. The diode indicated in blue is present when the 29.5-30.0MHz range is selected but it must be absent for the 27.5-28.0MHz range to indicate correctly on the counter.
18252
To make this work we have to somehow logically add D101 and D107 when the "+0.5" switch is pressed, and remove D35 from the circuit at the same time. No major changes can occur to the remainder of the Counter Unit as programming for the rest of the band ranges will be disrupted. If we want to re-use the push-button front panel switch and the associated logic, we have to make the "29" line active with 9V when either the 27 or the 29 band switch position is active, then use those signals on the Counter Unit to steer the band logic.
Proposed change to the RF Unit (Coil Pack):
18254
Note the diode in red. It allows for re-use of the 29 line but prevents the 29MHz control signal from interacting with the Aux lines on the Counter Unit.
Modification details of the board to follow.
Some initial thoughts on the switching arrangement required for the diodes in Post #68:
To re-use the 29.5 range for 27.5, we need to add D101 and D107 to the circuit. A method to electronically control this is required. An NPN switching transistor (2N2222, 2N3904) is ideal. It can be driven from the "29.5" line (diode to base resistor preventing C-B leakage) and is run in an emitter follower configuration. The collector ties to the anode side of the "Aux" band supply bus (see the center portion of the diagram in Post #62). The emitter is in turn tied to the anodes of D101 and D107. Dead-bug construction atop the Counter Board should work well for this.
Conversely, the only time we want D35 out of the circuit is when the Aux band line is active AND the "+0.5" switch is engaged. A PNP transistor run in common collector configuration (emitter to the 29.5 line; collector to the anode of D35) looks to be the best way to accomplish this, Base will be driven from the Aux line via the same diode-resistor arrangement as the other transistor. An NPN is OFF when base current is present and ON when it's not. As long as the Aux line isn't active, the circuit will behave as OEM. Selecting Aux and pushing the "+0.5" switch will turn the transistor OFF and remove D35 from the circuit.
At least that's the present theory. It may become more involved if I haven't figured all the angles just right.
Did a bit of removal, soldering and re-installation today. Shown is the added diode on the underside of the RF Unit (Coil Pack Board):
18256
A 1N914, 1N4148 or similar can be used here. It's going to switch DC only so noise factor isn't an issue.
Per my previous post "It may become more involved...": Apparently it has. Did a DC check of the modification and the "+0.5" switch is doing its thing on both the Aux and the original bands on which it was active. Unfortunately, I lost the Aux band. Remember I mentioned D35? It was removed and the setup tested. Still no joy. I happened to look at the schematics again and see that D26 is active on all 10M segments but isn't supposed to be when the Aux band is active. Next bout with the desoldering station will be to pull it and test my theory.
Turns out this gets more convoluted but at the same time, potentially easier to implement:
After a bit more study and experimentation: If the diode in the post above is added to the RF Unit and D26/D44 are removed from the Counter Unit, then the Aux band works perfectly on both its base range and with the "+0.5" switch depressed. We don't need to add D101 or D107 to the Counter Unit as mentioned earlier, either. The matrix lines are properly switched for the required 500KHz shift simply by 9VDC appearing on the 29.5 line, as it will after the RF Unit mod.
Caveat: D26/D44 MUST be reconnected for the 28 and 29MHz band segments to function, and the Aux band WILL NOT function if they are. D26 activates a required PLL Preload bit for all the 10M segments, while D44 has all the 10M switching lines tied to it through a series of other diodes. It ultimately sets the second digit of the display itself (8+ MHz, via BCD logic). This isn't needed for the Aux band in question and if present results in gibberish on the readout.
Which brings us to design of a switching mechanism. (This series of posts is beginning to resemble an electronic scratchpad but the experiments may help others understand how these subsystems of the rig work in concert. I can leave them as-is or edit the series with just the pertinent mod details when finished.)
Logically, what's needed is to omit D26/D44 when the Aux bandswitch line is active. Otherwise, we don't care. Thoughts are to use a pair of PNP small-signal transistors in common-collector configuration. Roughly sketching this out (with mini schematic and pictures to follow): The cathodes of D26 and D44 are lifted from the PCB and each is tied to the emitter of a 2N3906 transistor. The collectors of each transistor go in the now-vacant cathode holes. Each transistor base has the cathode of another 1N914/1N4148 tied to it. Anodes are joined together; a 4.7K, 1/4w resistor connects to them. The other end of this resistor goes to the Aux line at the spot which supplies the cathodes of optional diodes D105-D110. Sleeving is used to prevent unwanted contact between existing circuitry and the new components.
Theory: A PNP conducts from its emitter to collector as long as no base current flows. When base current appears, the device turns OFF. Positioning the transistors at the indicated points in the circuit and using diodes on the bases ensures that no current can flow in the reverse direction, potentially causing problems elsewhere. Desired signal conditions only. During normal 10M operation, current flows through the transistors as normal. When Aux is selected, they're effectively removed from the circuit and no voltage appears at their respective logic gates.
If I see evidence of leakage I may end up adding diodes to the collector side of the devices in a follower configuration - or I may do this right out of the gate to ensure reverse current leakage from Q9 and Q14 cannot occur. All depends on whether or not the gates will reliably change states with a bit more introduced voltage drop.
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