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N8YX
08-01-2009, 08:18 PM
Thread to discuss modifications which add or change functionality of classic gear and keep it viable today.

The Kenwood R820: Getting more coverage.

I have a few of these things kicking around the shack, and use two in conjunction with a pair of TS820S transceivers. The third sees duty as a general-coverage Ute monitor of sorts, and it no longer covers the ham bands.

Primarily, there are two ways to extend or change coverage of an R820 - and some of the tricks I'll discuss can be applied to a TS-820S as well...especially the WARC-band mods.

[highlight:18ejtptw]Method 1 - re-crystal and add the "Aux" Band components[/highlight:18ejtptw]

The 820-series PLL/VCO/counter arrangement uses one crystal oscillator/VCO combo per band, and it's easy to swap crystals on the PD board to get different coverage ranges - but you'll need a solder sucker to do it properly. The reference oscillator crystals are on 500KHz multiples and the required frequency for a given band is calculated by:

Fc = 5.5 + lower band edge

In this example, we want coverage of 12M, starting at 24.5 MHz. Thus, 5.5 + 24.5 = 30.0000 MHz.

The crystals used are HC-18/U or HC-49/U (wire lead), 20-30pF series capacitance. (eBay's yer buddy in some cases. I bought an entire bag of the rocks required for 12M for ~$3 and will pass along the savings to anyone who wishes to mod their 820 line. Contrast this to $20 per crystal from ICM!)

I changed most of the band crystals in my "Ute" '820 and will have the following bandswitched coverage when done:

2.0-2.5 MHz
3.0-3.5 MHz
6.5-7.0 MHz
13.5-14.0 MHz
15.5-16.0 MHz (old WWV spot)
21.5-22.0 MHz
26.5-28.0 (in three bands)
29.5-30.0 MHz (left stock...more on this in a bit)
25.5-26.0 MHz - added to the "Aux" spot

This gets me the 120M, 90M, 41M, 22M, upper end of the 19M, 13M and 11M SW broadcast bands...as well as the area directly above and below the Class D CB Radio service. It's useful to be able to find who's tearing up 10M on occasion...

Adding a band to the "Aux" spot requires adding a crystal, a 3.3K resistor, 5.6K resistor and a 150pF ceramic disc capacitor to the PD board. You need to add a 9/32" tunable coil of the correct inductance to the "T11" spot on the VCO board, along with four (or five, depending on band) pF-range ceramic disc capacitors. You must remove the Coil Pack board and add an ANT and two MIX slug-tunable coils, the value of each depending on the new band added.

Word of Advice: Acquire a junked TS820S and salvage the needed ANT coil from its Coil Pack board, and required the VCO coil from the VCO board. You can also get the two 9/32" MIX coils from this board...but you're going to have to rewind them. I used a total of 8 turns on each of the new coils for the 25.5 MHz band; this should resonate 12M with ease. On a previously converted '820 I would ALL the coils from scratch. A dip meter is invaluable here. It was still a PITA.

Follow the service manual procedure for adjusting the VCO and Coil Pack coils.

Your TS-820S can be similarly modified. QST (February 1983) carried a detailed article; much of which I've described here is loosely related.

[highlight:18ejtptw]Method 2: Electrickery with the Converter unit[/highlight:18ejtptw]

Kenwood did a neat trick with this receiver: They built a SWBC receiving converter which outputs to 10M and which is capable of preloading the counter, thus giving accurate readout of anything covered by the converter. We're going to take advantage of their design logic to get some extra coverage in a relatively easy fashion.

See the secondary "Band" knob in the picture below? Kenwood tied its activation line to just the 29.5 MHz bandswitch position, but it'll work on the other 10M spots.

http://www.rigpix.com/kenwood/r820.jpg

Arm yourself with a service manual, schematics and a soldering iron...and a few 1N4148 diodes. That's all this mod requires.

First, remove both top and bottom covers and locate the main bandswitch. Look for a WHT/BRN wire which runs from the 29.5 MHz contact to the top rear contact on the SWBC bandswitch. (It's at the anode end of a 1S1555 diode which is connected to two of the wafers.) Unsolder the WHT/BRN wire at the anode end of the diode then solder it to the anode of one of the 1N4148 diodes you sourced for this project. Solder the cathode end of your new diode/wire arrangement to the anode of the 1S1555. Use heat shrink tubing on the diode and wire.

Now locate the 29.0 MHz (WHT) and 28.5 MHz (GRY) bandswitch wires. Peel a little insulation back at the midpoint of each and solder the anode of a 1N4148 to each. Now solder the cathodes to the anode of the 1S1555, just like you did above. Again, use heat shrink and a little electrical tape on each of the connections. Check for shorts, then power up the receiver. You're hearing stuff...but...the counter is indicating incorrectly at this point!

There's a fix for that. Study the service manual and the schematic of the PD/VCO board. Then look at what Kenwood did for the 28, 28.5 and 29 MHz bands that they didn't do for the 29.5 MHz band.

That's right, diodes. These are used to preset bandpass select line "B4" of the counter but aren't needed if voltage is present as a function of the secondary band-select circuit.

Remove the PD/VCO assembly, invert it and remove the 5 sheet metal screws that secure the cover. Now locate D21 and D22, near the "B1-B4" posts. Snip their anode ends and mode them out of the way, then replace the VCO cover and reinstall the module, connecting the PLL1-PLL5 connectors as you go. Check your work...fire the set up and look smug. It's now displaying properly.

Each of the four "SWBC" bands employs a tuned bandpass filter, and these must be retuned to allow broader coverage of the "expanded" ranges. I find it best to stagger-tune them with the aid of a sweep generator but you can do it manually if necessary. Just peak on atmospheric noise or signal at several places throughout the whole 1.5 MHz range. (Refer to the R820 service manual for details on the procedure and component identification.)

[highlight:18ejtptw]Method 3: A little of both[/highlight:18ejtptw]

The converter's crystals can also be changed to move the coverage around a bit. I would try to stay within 1.5 MHz of either side of "stock", which is as follows:

5.9-6.4 MHz
9.4-9.9 MHz
11.5-12.0 MHz
17.7-18.2 MHz

(Yes, it'll cover 17M "out of the box". I took advantage of this and modified my TS-820S to cover 17M, and in doing so I specified the new PD oscillator crystal frequency such that it allows accurate tracking of the R-820's tuning range...thus enabling true 'twins' operation on the 18 MHz band.)

The crystals required to modify the converter board are HC-18/U or HC-49/U; 20-30pF series capacitance...and their frequency is calculated accordingly:

29.5 - lower band edge

Thus, for coverage of 7.0-7.5 MHz (at the old "49M") spot, you'll need a 22.0000 MHz crystal. Again, an easy eBay find.

Lastly -

One can modify the WWV/JJY band position of either the R-820 or the TS-820S for 10.0-10.5 MHz operation, thus covering 30M. The February '83 QST article goes into detail about this modification; I'm going to do it to my second "pair" of twins and add 12M to each in the process.

Should anyone find this writeup useful and want pictures and/or help, I'll be glad to assist.

KG4CGC
08-06-2009, 03:18 AM
Fine business.

N8YX
08-06-2009, 02:28 PM
Fine business.
I just got parts in the mail to convert both of my FT-901's RF boards to a DBM (instead of a dual MOSFET) arrangement. Likewise its speech processor board, though I am still awaiting band crystals for the sets. Gonna WARC 'em...

N8YX
08-08-2009, 12:28 PM
More '820 nooz:

Some of the crystals I needed arrived yesterday. Changing them was easy. Getting the display to read the correct frequency for the new 10 MHz band was another matter entirely, though the actual modification was simple once the circuit was understood.

Refer to my original post about the SWBC as used in the R-820. Its 31M band crystal is exchanged for a 19.500 MHz unit, which is actually an OEM value for the 20M band segment. But the counter now reads "0.000.0" instead of "10.000.0".

The fix is as follows:

Note the blue wire on the lower rear portion of the SWBC band switch; this with the receiver upside down and the front oriented towards you. There is a wire jumper which connects the bandswitch terminal with the blue wire to the next terminal to its right. Desolder the blue wire, then move it one terminal to the left (white and purple wire). Solder it there. Next, run a jumper from the terminal where the blue wire was to the terminal with the brown wire, immediately to its right.

Check your work and power the receiver. It should indicate "10.000.0" to "10.500.0" throughout the tuning range, but if you dip below 10.000 it'll read "19.999.9", etc. There isn't a cure for this, as we've hard-wire-selected the next highest counter prescalar. (Incidentally, as delivered from Kenwood the high end of the 29.5 MHz segment reads "20.000.0" when you tune past 29.999.9...on ALL '820-series equipment. This is what you get with a counter of a scalar/bandpass design.)

Re-peak the band-pass filter coils on the converter board as shown in the service manual. The '820 I converted has good sensitivity but I'm seeing a pair of images...one at 10.130 and another at 10.115. When I find the offenders I'm going to construct a series-tuned trap and place it across the output of the 31M bandpass filter to ground.

Speaking of bandpass filters...if you really get carried away with shifting the converter crystal frequencies (like I did), odds are you're going to have to change some capacitor values in order to get the coils to tune properly. The 49M spot on mine now covers 7.5-8.0 MHz and I'm going to swap the existing caps for a bunch with slightly lower values. Either that...or pony up $40 for two more crystals, one at 13.000 MHz (to allow the 40M spot to cover 7.5-8.0) and 23.000 MHz (to allow the converter to cover 6.5-7.0, which is very close to its designed range).

As with anything, there's always backlash. Mine came in the form of a worn gear drive on the VFO. I spent the better part of last evening and until around noon today rebuilding the mechanical portion of things to ensure a smooth, lash-free drive.

If you're a fan of the Kenwood or Yaesu hybrids, I'll give some advice:

1) Mechanical components wear, faster without lube;
2) If your rig's VFO sits pretty much in one spot its whole life, this may not be a problem;
3) If the rig was heavily used and not cared for, wear certainly will be an issue at some point.

In the '820's VFO assembly, an idler gear set is used to reduce the rotational motion between the tuning shaft and the VFO capacitor rotor shaft. Each end of the idler gear shaft is held captive in one of two brass plates which comprise the support assemblies for the drive unit. If the hole becomes elongated or wears oversize, the resulting slack (albeit small) is enough to thoroughly muck up the tuning...to the point that getting an SSB signal "dead on" is extremely difficult.

My solution is to buy up these parts as I find them (cheap!) and cannibalize as necessary. Of course, I plan on keeping my hybrids around for a while.

The R-820's 20M band spot now tunes from 13.5 to 14.0. I'll see if I can hear any HiFer beacons (including Kelli's) around 13.555 with the rig...

n4aud
08-08-2009, 08:55 PM
Where are you getting your crystals?
I'd like to have a couple of fixed channels on my TS-520 on frequencies where I participate in nets.

N8YX
08-09-2009, 05:26 AM
Where are you getting your crystals?
I'd like to have a couple of fixed channels on my TS-520 on frequencies where I participate in nets.
For the custom-made rocks: ICM, primarily. I've also found them at a number of places online, both new and surplus.

Let me know the frequencies you need. Ye Olde Junque-Box may yield a surprise or two.

N8YX
08-09-2009, 11:26 AM
I'm sitting here in the shack/computer lab enjoying the fruits of my labors vis the eBay "rescue" R-820. Seller stated it was blown up, fried, kaput, missing parts, etc...

The only missing part I'm aware of at this time is the shield which covers the IF-A (filter) board, and I've laid out a piece of double-sided copper-clad board with the shapes necessary to construct another. That's probably easier than making one from sheet metal and the results will be the same.

The VFO backlash problem was solved by preloading each half of the split gear assemblies by one tooth as the drives were being put together. That, and a careful selection of end plates married to reduction drives resulted in a smooth-tuning unit in the radio and two more "spare" VFOs, ready to go if necessary. No slop; no backlash.

Total investment in the rig was $227 + $20 for a spare counter board + $10 for some hardware...and maybe $140 on extra band crystals. I still may purchase a couple more and some filters for the rig. For those unfamiliar with the receiver, it was the first Kenwood radio to introduce Variable-Bandwidth Tuning, and it works well. But not as good as a nice, sharp-skirted filter. Since this rig is primarily used outside the ham bands, I'm thinking about adding a 1.8 KHz B/W SSB filter...a 6 KHz AM filter...and either a 4 KHz AM filter (for synchronous AM detection) or a 500hz CW filter (for 425-shift RTTY). Of course, the rig's IF Shift is inactive while in AM mode...thus necessitating yet another mod if I'm to use it for SAM detection. Likewise, the filter board's switching logic will need a bit of re-engineering in order to be able to select the correct filter based on mode.

Next up in the '820 mod series is adding 30 and 12M WARC to a TS-820S/R-820 pair. The Yahoo Group "Kenwood Hybrids" which I'm a member of has at least one other gent who's modding his '820, and I'm thinking about sending a link to this thread to the membership at large.

n4aud
08-11-2009, 10:16 AM
Where are you getting your crystals?
I'd like to have a couple of fixed channels on my TS-520 on frequencies where I participate in nets.
For the custom-made rocks: ICM, primarily. I've also found them at a number of places online, both new and surplus.

Let me know the frequencies you need. Ye Olde Junque-Box may yield a surprise or two.

I participate in a couple of nets on 3947 khz. Kenwood says that requires a 5054.5 crystal.

N8YX
08-11-2009, 10:35 AM
I participate in a couple of nets on 3947 khz. Kenwood says that requires a 5054.5 crystal.
Just checked two online sources which list a bunch of surplus rocks - no dice.

Will check my stash and let you know what I come up with.

n4aud
08-12-2009, 09:20 AM
Thanks.

N4VGB
08-14-2009, 09:01 AM
I object to this thread title, the TS-820S is one of my newest radios!

A proper "oldie" is pictured below.

AF6LJ
08-14-2009, 10:10 AM
This has been a good thread and informative to boot :)
My 820 will receive some quality time this weekend.
I'm replacing the hot melt glue bead on the VFO tank coil and see what the outcome is before retuning it.
Maybe I won't have to.

N8YX
08-14-2009, 02:17 PM
I object to this thread title, the TS-820S is one of my newest radios!

A proper "oldie" is pictured below.
You want some ART-13 "spares"?

I have a whole box of cannibalized stuff. I'll be glad to send it your way...

N4VGB
08-14-2009, 04:39 PM
I object to this thread title, the TS-820S is one of my newest radios!

A proper "oldie" is pictured below.
You want some ART-13 "spares"?

I have a whole box of cannibalized stuff. I'll be glad to send it your way...

Sure thing OM. I'll even have UPS pick up the box if you'll send the size and weight. There's no such thing as having too many spare parts for the old stuff. I used to flip that preselect switch on the ART-13 all the time to WOW newbie hams over the autotune. Then I discovered what a PITA repairing the autotune was, it never got moved again unless necessary.

WTKX
08-14-2009, 06:47 PM
Fine business.
I just got parts in the mail to convert both of my FT-901's RF boards to a DBM (instead of a dual MOSFET) arrangement. Likewise its speech processor board, though I am still awaiting band crystals for the sets. Gonna WARC 'em...

I have this very nice FT-902DM with issues that I really need to get busy with one of these days. Have the FTV 901R transverter for it and the FV-101Z VFO too. The RX works well, just no output. But I want to do a full on restoration with mods. The older high end hybrid radios are really interesting.

So I will be bothorin' you! Eventually. Got any service riser cards? :mrgreen: Been gleaning info off the Yahoo Group for about 6 months. And the Fox Tango site is good.

So far I have only breathed life back into a couple of Ten Tec rigs, and that went well. I have another Omni-D project right now.

N8YX
08-14-2009, 08:39 PM
I have this very nice FT-902DM with issues that I really need to get busy with one of these days. Have the FTV 901R transverter for it and the FV-101Z VFO too. The RX works well, just no output. But I want to do a full on restoration with mods. The older high end hybrid radios are really interesting.

So I will be bothorin' you! Eventually. [highlight:32yusln2]Got any service riser cards[/highlight:32yusln2]? :mrgreen: Been gleaning info off the Yahoo Group for about 6 months. And the Fox Tango site is good.

So far I have only breathed life back into a couple of Ten Tec rigs, and that went well. I have another Omni-D project right now.
But of course I do... :lol:

One of my current operating positions consists of an FT-901DM, FV-901, FTV-901R (w/ all modules), YR-901/YK-901, YO-901, FC-901, SP-901P and SP-901. I recently snagged a few other pieces off eBay and have another complete outfit (sans RTTY reader and scope) plus a couple other surplus pieces which I'm planning to sell. The second '901 is going to get WARCed (12 and 30M) while the other is going to get 17M and as-yet-undecided "Aux" band.

I also have nearly a complete radio's worth of spare boards and other pieces. These will be used for modification purposes, one board at a time. I'm going to cannibalize the VCO, PLL and XTAL assemblies for all of the components that I'll need to add WARC coverage to the other sets.

I had a bunch of 902 stuff and sold it a year or so back. Then I set the 901 up and fell in love all over again. That's the rig which always "wowed" me when I was in high school, but who could afford $2K at that time?

N8YX
08-14-2009, 08:42 PM
Sure thing OM. I'll even have UPS pick up the box if you'll send the size and weight. There's no such thing as having too many spare parts for the old stuff. I used to flip that preselect switch on the ART-13 all the time to WOW newbie hams over the autotune. Then I discovered what a PITA repairing the autotune was, it never got moved again unless necessary.
Let me gather up what I have and I'll let you know. I -think- I still have all of it; there were three -13s which were cannibalized some time back and I saved the majority of the pieces.

Got a bunch of period-era tubes - 1625s, 807s and so forth. If you or anyone else can use 'em, let me know.

N4VGB
08-14-2009, 09:28 PM
Sure thing OM. I'll even have UPS pick up the box if you'll send the size and weight. There's no such thing as having too many spare parts for the old stuff. I used to flip that preselect switch on the ART-13 all the time to WOW newbie hams over the autotune. Then I discovered what a PITA repairing the autotune was, it never got moved again unless necessary.
Let me gather up what I have and I'll let you know. I -think- I still have all of it; there were three -13s which were cannibalized some time back and I saved the majority of the pieces.

Got a bunch of period-era tubes - 1625s, 807s and so forth. If you or anyone else can use 'em, let me know.

FB on the toobs also but I think I should pay you something on them. Let me know.

N8YX
08-19-2009, 10:59 AM
Some updates:

Got a handful of crystals delivered to me from ICM a couple days ago; swapped the stock 80M rock for an 8.5000 MHz unit (for 3.0-3.5 MHz coverage), changed the WWV/JJY crystal for one which covers 15.5-16.0 and changed the 40M crystal for one which allows 7.5-8.0 MHz coverage. On the converter board, two changes were made - first, a retrofitted 22.000 MHz crystal in the SWBC "49M" spot was removed and one which facilitates 6.5-7.0 MHz reception was installed, and the OEM 11.8 MHz (17.7-18.2) "19M" crystal was changed for an 11.000 MHz unti...thereby adding coverage of 18.5-19.0 MHz.

A realignment of the 80, 40 and WWV ANT/MIX coils got those new bands working up to snuff, and an adjustment of the converter board's bandpass filters took care of the others.

Audie - no luck in the junk box for a crystal for you. Call Sara at ICM and she'll hook you up. I highly recommend them.

Mack - I have to root through the boxes of parts and ferret out all of the ART13 components; it'll be a month or two before I've collected all of them.

Next up: Drifty VFO in an FT-902DM.

One wonders if the "fix" isn't already in:

http://www.dooleystreasurechest.com/wb5tka/yaesu.htm

Need some of the N220 caps as discussed in the linque. Anyone have a few?

N4VGB
08-19-2009, 11:33 AM
Mack - I have to root through the boxes of parts and ferret out all of the ART13 components; it'll be a month or two before I've collected all of them.



Definitely no hurry, take your time.

n4aud
08-19-2009, 07:09 PM
Some updates:


Audie - no luck in the junk box for a crystal for you. Call Sara at ICM and she'll hook you up. I highly recommend them.


No problem, and thanks for the tip. I think I actually called them once but like a lot of things I kind of let it fall to the wayside and forgot about it.

N8YX
09-09-2009, 07:12 AM
Bumping this topic back up:

I got hold of an FT-902DM as part of an eBay auction several weeks back. Plans are to sell it to my friend Steve, along with an FC-901 tuner which came with the package.

Upon placing the thing on the bench and checking it over, I found that it drifted. Horribly. We're talking on the order of 5KHz in 24H from a cold start.

Seeking information as to any possible causes, I ran across the following site:

http://www.dooleystreasurechest.com/wb5tka/yaesu.htm

Digesting the contents therein, I went to work. First thing was to get rid of all the "suspect" N750 temperature-compensating caps in the VFO circuit and replace them with new, NP0 parts as a test. Wait...it's still drifting as before. :evil:

We began to dance the dance, that rig and I. When the solder smoke cleared, two things were evidenced:

1) The compensating caps are not the problem;
2) The rig drifts an enormous amount...moreso that a simple 5-6pF thermally-induced delta would cause.

Further probing revealed a control line (the RIT/XIT feed) which was fluctuating in voltage. Hmmm...dirty switches? Yep - a little cycling and cleaning fixed that problem but there is still a bit of drift. About 2KHz, rather than 5. Swapping the NP0 caps with new components got the drift down to around 400hz for a 24H period, with 300 of that coming in the first few minutes after power-on. Back in spec...but...the counter/display won't zero against WWV.

Drifty crystal?

New ones ordered and installed...and now I cannot get the display adjusted down past 10.004.4. :chin:

Schematically speaking, we probably have yet another bad NP0 cap; this one a 20pF across the crystal trimmer.

Updates will be forthcoming after the offender is swapped for a new part. Those of you with a 902, 101Z, 107 or 301 may wish to take note of what I've found with regards to component aging and drift...

http://www.dooleystreasurechest.com/wb5tka/images/PICT0008.JPG

AF6LJ
09-09-2009, 07:46 AM
Not at all uncommon for radios that are old enough to vote then some. :)

Good luck, looking forward to reading the next update.

n4aud
09-10-2009, 11:59 PM
Yeah, I'm following along so keep us updated on your efforts with this rig.

N8YX
09-20-2009, 07:57 PM
Yeah, I'm following along so keep us updated on your efforts with this rig.
All fixed.

The 20pF NP0 was indeed "bad"; I replaced it with an 18pF NP0 unit, reassembled the rig and turned it on then let the rig sit for a few hours...then netted the counter on WWV.

But there was still a drift problem, and it was intermittent. That indicated a fluctuating voltage somewhere, most likely the VFO power supply or some reference line. The RIT, XIT and RF ATT switches seemed to affect this somewhat...dirty switch contacts, perhaps? I sprayed them with F5 Faderlube then added a drop or two of DeOxIt per switch. Upon reassembly - and after carefully tightening down all the chassis hardware - I fired the rig up with the heaters "On".

Yaesu specs the '902 as having a 400Hz drift within the first hour after warmup, then 100Hz per hour afterwards. Mine went 400Hz over three hours, after which I parked it on 14.250.0 and left it sit. From ~7PM Friday evening through 11AM Saturday morning it drifted a total of 500Hz, which is well within Yaesu's specs.

I could probably get the drift down even further by replacing a few more caps but the rig's new potential owner is happy with it as is.

My '901 spoiled me, though, and I let Steve know this...that's why I went after the '902's drift problems with such vigor. Snap the power "On" and after a 200Hz initial drift it stays put on a given frequency - I'm talking weeks worth of stability, too. The internal memory module and external synthesizer both seem like a moot point with this particular radio.

AF6LJ
09-20-2009, 10:00 PM
Cool
Glad to see it's working resonably well. :)

N2NH
09-20-2009, 10:06 PM
Bumping this topic back up...

http://www.dooleystreasurechest.com/wb5tka/images/PICT0008.JPG :drool:

That is a beautiful beastie! Someday I got to get a classic rig. Besides the SB-104A and HW-8. ;)

N8YX
09-21-2009, 07:42 AM
That is a beautiful beastie! Someday I got to get a classic rig. Besides the SB-104A and HW-8. ;)
Those are neat rigs in and of themselves. How about a hardware hack for the HW8 which converts it to 160-30-17-12 or 30-17-12-10? Or puts two of them (one converted) in the same largish enclosure and gives you 8 bands..a common CMOS keyer, metering circuits and possibly a PA?

I have two, and while electrically excellent they leave a bit to be desired...cosmetics-wise. Thus, they might be good candidates for use in a projust such as this.

Moving back to the Yaesus for a bit:

There's just something about the '901 that I prefer. The '902 gives you the WARC bands and incorporates all of the updates which some feel are necessary for a robustly performing, reliable rig...but there's nothing which prevents a '901 owner from modding his or her rig to '902 "specs".

Yaesu incorporated a display in the '902 which automatically shifts the readout by an offset that is based on the selected sideband; in the '901, one must manually calibrate the readout when changing modes. This really isn't a big deal after you do it a few times. The biggest differences in the two - performance-wise - are the front-end circuits. The '901 used a dual-MOSFET arrangement and the '902 used a balanced mixer.

I bought a spare "carcass" (rig sans power transformer, tubes and knobs) for parts a couple years back, and its various boards are going to be used as parts sources for the XTAL, PLL and VCO boards in the two functional units which I'm restoring and upgrading. There's also a spare RF board on-hand; I'm going to modify it (and the two other "installed" '901 RF boards) to the '902 spec over the winter. Likewise, I'm going to modify the NB, speech processor, Rectifier "C" and AF boards to bring them up to latest revision.

Pix and details as I go...

http://www.jg2oaj.com/g/FT-901D.jpg

AF6LJ
09-21-2009, 09:18 AM
That is a beautiful beastie! Someday I got to get a classic rig. Besides the SB-104A and HW-8. ;)
Those are neat rigs in and of themselves. How about a hardware hack for the HW8 which converts it to 160-30-17-12 or 30-17-12-10? Or puts two of them (one converted) in the same largish enclosure and gives you 8 bands..a common CMOS keyer, metering circuits and possibly a PA?

I have two, and while electrically excellent they leave a bit to be desired...cosmetics-wise. Thus, they might be good candidates for use in a projust such as this.

Moving back to the Yaesus for a bit:

There's just something about the '901 that I prefer. The '902 gives you the WARC bands and incorporates all of the updates which some feel are necessary for a robustly performing, reliable rig...but there's nothing which prevents a '901 owner from modding his or her rig to '902 "specs".

Yaesu incorporated a display in the '902 which automatically shifts the readout by an offset that is based on the selected sideband; in the '901, one must manually calibrate the readout when changing modes. This really isn't a big deal after you do it a few times. The biggest differences in the two - performance-wise - are the front-end circuits. The '901 used a dual-MOSFET arrangement and the '902 used a balanced mixer.

I bought a spare "carcass" (rig sans power transformer, tubes and knobs) for parts a couple years back, and its various boards are going to be used as parts sources for the XTAL, PLL and VCO boards in the two functional units which I'm restoring and upgrading. There's also a spare RF board on-hand; I'm going to modify it (and the two other "installed" '901 RF boards) to the '902 spec over the winter. Likewise, I'm going to modify the NB, speech processor, Rectifier "C" and AF boards to bring them up to latest revision.

Pix and details as I go...

http://www.jg2oaj.com/g/FT-901D.jpg
Maybe next year I may have to go hunting for one of these, they get a lot of positive reviews and they look really good.

N8YX
09-21-2009, 10:13 AM
Maybe next year I may have to go hunting for one of these, they get a lot of positive reviews and they look really good.
I'm going to write an Eham review for both the 901 and the 902.

Here's a bit of advice when it comes to shopping for one:

Get hold of a rig that has excellent cosmetics if possible...a working transformer and counter...and the rest doesn't matter. Almost all of the parts are still available (sans a few obsolete ICs which can still be found). Most of the troubles you're going to encounter are as follows:

1) Dirty bandswitch contacts;
2) Dirty potentiometer wipers and pushbutton switch contacts;
3) Bad electrolytic capacitors, especially those used in the HV sections;
4) Aged NP0s, temp compensating ceramics
5) A questionable 100pF, 1KV mica coupling cap on the PA input board.
6) Intermittent relays
7) Burned-out lamps
8 ) Soft driver and/or PA tubes
9) Miscellaneous mechanical isses

All of these can be fixed.

I have a spare SP-901P, FV-901, FTV-901R (w/ 2M module) and an FC-901. The accessories are all surplus to my needs, and if you (or anyone else reading this) are interested in the stuff, PM me.

AF6LJ
09-21-2009, 10:26 AM
Maybe next year I may have to go hunting for one of these, they get a lot of positive reviews and they look really good.
I'm going to write an Eham review for both the 901 and the 902.

Here's a bit of advice when it comes to shopping for one:

Get hold of a rig that has excellent cosmetics if possible...a working transformer and counter...and the rest doesn't matter. Almost all of the parts are still available (sans a few obsolete ICs which can still be found). Most of the troubles you're going to encounter are as follows:

1) Dirty bandswitch contacts;
2) Dirty potentiometer wipers and pushbutton switch contacts;
3) Bad electrolytic capacitors, especially those used in the HV sections;
4) Aged NP0s, temp compensating ceramics
5) A questionable 100pF, 1KV mica coupling cap on the PA input board.
6) Intermittent relays
7) Burned-out lamps
8 ) Soft driver and/or PA tubes
9) Miscellaneous mechanical isses

All of these can be fixed.

I have a spare SP-901P, FV-901, FTV-901R (w/ 2M module) and an FC-901. The accessories are all surplus to my needs, and if you (or anyone else reading this) are interested in the stuff, PM me.
I am looking forward to reading the review :)

N8YX
09-21-2009, 04:49 PM
In case anyone gets hold of one of these rigs and it has burned-out meter bulbs...I just placed an order for 45 of them from Farnell Electronics in the U.K. I'll be happy to send a few out to anyone who needs them.

http://foxtango.org/FT901/graphics/FT-901%20Meter%20Lamps.JPG

N8YX
09-23-2009, 07:59 PM
I am looking forward to reading the review :)
Reviews of both models now up on the site.

In a nutshell:

People ought to critique a properly functioning example of a piece of vintage gear instead of some "hamfest special" version of such. :roll:

AF6LJ
09-23-2009, 10:40 PM
I am looking forward to reading the review :)
Reviews of both models now up on the site.

In a nutshell:

People ought to critique a properly functioning example of a piece of vintage gear instead of some "hamfest special" version of such. :roll:
Thanks I shall read it tomorrow over morning coffee :)

AF6LJ
09-24-2009, 08:12 AM
Good writeup.
Thanks.
:)

N8YX
09-24-2009, 08:17 PM
Diving back into more Yaesu goodness:

Decided to drag the FT-901 onto the bench this evening and treat it to a relamping, seeing how my order of bulbs from Farnell (UK) was sitting on my front porch when I arrived home this afternoon. Once I figured out how to extract the meter and disassemble it, things went fairly smooth. A caution: Replacement axial lamps may be slightly longer than the Yaesu originals shown in the picture above; that being the case, lead dress is important so as to prevent shorts to the meter frame.

Once the rig was back together and powered up, it became evident that a bunch more work must still be done - but at least it's receiving signals this evening.

N8YX
09-25-2009, 08:44 AM
Worked with the rig a bit more last evening and it's evident that the AGC selector and RF gain controls aren't doing what they're supposed to.

Searching around a bit led me to this topic on the Fox Tango forums:

http://www.foxtango.org/phpBB2/viewtopic.php?t=123&highlight=agc

Dirty switches. Seems there ain't no end to them things ... :wall:

My evening will now be spent with a can of Faderlube F5 and a squirt bottle of DeOxIt.

In diagnosing the problem, I changed the "Slow" AGC-decay time-constant capacitor (on the IF board) from 2.2 to 3.3 uF. It's a tantalum part, and they've been known to go bad over time. This one probably isn't, but 'slow' AGC as implemented on the 90x-series isn't slow enough. I've really become spoiled with the Kenwood 820 AGC design.

N8YX
09-27-2009, 08:11 AM
It wasn't the switches.

Spent Friday and Saturday dissecting the front panel and switch assembly, removing the "suspect" switch and installing a known good unit from my parts stash. Still no apparent AGC action, although a check with a meter shows proper voltages on the various control and output terminals on the IF board.

Swapping that board for another (known good) unit didn't fix the problem, either...so it's somewhere in the radio's chassis. :think

N8YX
09-27-2009, 10:04 PM
AGC problem fixed.

The AGC line runs from the IF board to the RF board, and another connection runs to a buffer amplifier on PB1726A. This buffer - a 2SK19GR FET - serves to supply AGC voltage to the EXT VFO connector, so the rig's optional scanning VFO "knows" when it has landed on a busy channel.

If the FET (Q3101) shorts....it clamps the AGC line to ~1.0v and recovered signals will sound very harsh.

Replacing the device with a similar part off a junk board fixed the problem.

I'm going to leave the IF board's newly-replaced 3.3uF tantalum as-is; the "Slow" AGC action is much better than with the rig's original 2.2uF cap.

Now that the rig has been functionally restored, it's time to start hacking. First up: Modding the RF board to use an SBL-1 balanced mixer instead of dual MOSFETS. This will lower the IMD figure a bit and reduce the rig's noise floor by an additional 4-6dB.

N8YX
09-29-2009, 07:31 AM
The RF board will be the third "hack". The first involved changing a coupling capacitor (C511) on the AF board for better bass response...while the second addressed a problem with the pilot-lamp circuit.

Yaesu's original specs call out two different axial-lead lamps -

A fuse-type axial (VFO dial) rated 8v; 150ma
2x leaded axial (meter lights) rated 8v, 55ma

The OEM bulbs are very difficult if not impossible to find. What I did come up with is an 8v, 250ma fuse-type and the axial-leaded lamps from Farnell which were mentioned earlier in the thread. These are either 80 or 100ma. Two of them in parallel along with the resistance of the fuse lamp gives us ~2 ohms DC resistance. The original pilot-lamp circuit has a 24 ohm, 3w wirewound in series with the heater supply (~13vac w/ heaters "off") and that resistor now gets mighty darned hot dropping almost 10v across it!

What to do... :chin:

I ended up re-designing the circuit so the lamps are in series with each other, rather than parallel. (The meter lamps are still paralleled, though.) The resistor was omitted and the overall light output is approximate to that of my "stock" '901DM.

The lights appear to be be brighter on initial powerup then dim slightly a second or so afterward, presumably due to the DC resistance of the filaments increasing as they heat and thereby decreasing the current draw.

Board Consensus:

Should I put a low-value (5-10 ohm) resistance back in series with the lamp circuit, or leave it as-is? Any worries about inrush current or bulb longevity without a fixed resistance in the circuit? The 24-ohm unit when in series makes the lights too dim.

Discuss.

AF6LJ
09-29-2009, 08:26 AM
The RF board will be the third "hack". The first involved changing a coupling capacitor (C511) on the AF board for better bass response...while the second addressed a problem with the pilot-lamp circuit.

Yaesu's original specs call out two different axial-lead lamps -

A fuse-type axial (VFO dial) rated 8v; 150ma
2x leaded axial (meter lights) rated 8v, 55ma

The OEM bulbs are very difficult if not impossible to find. What I did come up with is an 8v, 250ma fuse-type and the axial-leaded lamps from Farnell which were mentioned earlier in the thread. These are either 80 or 100ma. Two of them in parallel along with the resistance of the fuse lamp gives us ~2 ohms DC resistance. The original pilot-lamp circuit has a 24 ohm, 3w wirewound in series with the heater supply (~13vac w/ heaters "off") and that resistor now gets mighty darned hot dropping almost 10v across it!

What to do... :chin:

I ended up re-designing the circuit so the lamps are in series with each other, rather than parallel. (The meter lamps are still paralleled, though.) The resistor was omitted and the overall light output is approximate to that of my "stock" '901DM.

The lights appear to be be brighter on initial powerup then dim slightly a second or so afterward, presumably due to the DC resistance of the filaments increasing as they heat and thereby decreasing the current draw.

Board Consensus:

Should I put a low-value (5-10 ohm) resistance back in series with the lamp circuit, or leave it as-is? Any worries about inrush current or bulb longevity without a fixed resistance in the circuit? The 24-ohm unit when in series makes the lights too dim.

Discuss.
I hate replacing bulbs;
With that said, I would add a small amount of resistance. The inrush current the meter lamps demand on start up will in a short time snuff out the VFO lamp in my opinion.

This lamp issue leaves itself open for some interesting hacks.
Like a solid state lamp starter.

N8YX
09-29-2009, 08:24 PM
RF board converted to use a DBM per PA0PGA. This duplicates the circuit as used in the FT-902. Though the "bench antenna" is nothing more than a 30' hank of wire, and it picks up every EMI/RFI source in the household, the receiver appears to be a bit quieter. I will post pix of the next one of these I do, as the "spare" board is going into my other (working) FT-901DM when it's finished.

Next up: Processor and NB mods. Yaesu's NB design - nice as it is - can be altered to more effectively deal with atmospheric QRN. Likewise, the processor can do with a redesign and gain-follower (J177 FET) addition.

Sue, I found an inrush-protector circuit which makes use of a 2N3904, a power MOSFET and a few other components. It'll handle a 1A load...I may add this to the rig when I get a couple of the MOSFETs in-hand.

AF6LJ
09-30-2009, 08:05 AM
RF board converted to use a DBM per PA0PGA. This duplicates the circuit as used in the FT-902. Though the "bench antenna" is nothing more than a 30' hank of wire, and it picks up every EMI/RFI source in the household, the receiver appears to be a bit quieter. I will post pix of the next one of these I do, as the "spare" board is going into my other (working) FT-901DM when it's finished.

Next up: Processor and NB mods. Yaesu's NB design - nice as it is - can be altered to more effectively deal with atmospheric QRN. Likewise, the processor can do with a redesign and gain-follower (J177 FET) addition.

Sue, I found an inrush-protector circuit which makes use of a 2N3904, a power MOSFET and a few other components. It'll handle a 1A load...I may add this to the rig when I get a couple of the MOSFETs in-hand.

Do you have a link to the PA0PGA mod I would like to see exactly what was done?

The inrush limiter sounds good, that's more or less what I had in mind. Cool :)

N8YX
09-30-2009, 10:15 AM
Do you have a link to the PA0PGA mod I would like to see exactly what was done?
But of course:

http://foxtango.org/Files/FT-901DMsg.pdf

Page 22, roughly 2/3 of the way through the document.

I used an SBL-1 for the conversion.

Rant:

See here - http://www.eham.net/reviews/mailto/75576

And here - http://www.eham.net/reviews/mailto/67317

My latest "project" was powered up last evening with the covers off and drifted less than 100hz total during the entire period it was left on.

"Overdriven audio"? Just who is in control of THAT, pray tell? :chin:

Sounds like one of the reviewers got himself an abused example...came straight out of CB-land and never touched a tube-final rig prior...or both.

/Rant

AF6LJ
09-30-2009, 05:38 PM
Do you have a link to the PA0PGA mod I would like to see exactly what was done?
But of course:

http://foxtango.org/Files/FT-901DMsg.pdf

Page 22, roughly 2/3 of the way through the document.

I used an SBL-1 for the conversion.

Rant:

See here - http://www.eham.net/reviews/mailto/75576

And here - http://www.eham.net/reviews/mailto/67317

My latest "project" was powered up last evening with the covers off and drifted less than 100hz total during the entire period it was left on.

"Overdriven audio"? Just who is in control of THAT, pray tell? :chin:

Sounds like one of the reviewers got himself an abused example...came straight out of CB-land and never touched a tube-final rig prior...or both.

/Rant
Thanks that was a good read, took a break while working on the 745, I shall post more on that later on.

N8YX
09-30-2009, 07:59 PM
Carrier Board, Noise Blanker Board, IF Board and another Audio Board modded this evening:

1) Replaced the 1S1007 diode-ring mixer components on the Carrier Board with a matched quad of 1N5711/HP-5082-2800 Schottky hot-carrier diodes. This cut a goodly amount of received hash out and is supposed to improve the transmitter IMD as well, but that remains to be seen. The carrier suppression has got to be checked but that's to be expected - this thing is due for a full alignment before I'm done.

2) Modded the speech processor on the NB board - installed a clipper across the output of Q206; removed the 2SC1815 follower and related components...then substituted a J177 P-FET and made associated circuit changes, including rewiring the front-panel processor-level control. This should give me from 0-30dB of processing; the OEM circuit was largely ineffective

Also added a 100K resistor on the NB Board to change the noise-gate timing, then pulled it back out as the gate was reacting adversely to normal band noise...creating an intermod condition. While the addition of the resistor helped the blanker to deal with ambient noise, it was a little too effective. "Ideal" is somewhere between 100k and infinity. I'll try other values later.

3) IF board - 0.1uF bead tantalum across C328, improving NB action on pulse (ignition) noise. Haven't heard any noisy ignitions go past tonight to test it.

4) Audio Board - dropped C511 from 1.0 uF to 0.47uF to .047uF, this to help bass response. Seems to work. My small external speaker doesn't have a lot of ooomph at the lower end, so I'll have to see how this works when connected to an SP-901.

Next up is a key-click and Rect-"A" / Rect-"C" arc-over protection mod and afterward it's into the radio's guts for a coupling capacitor change on the PA board. Then I'll start populating the VCO and XTAL boards with the components required to add 30 and 12M.

N8YX
10-01-2009, 10:39 PM
Today saw the conversion of the XTAL and VCO boards to accomodate the 30M and 12M WARC bands.

I bought a "parts rig" a couple years back, everything but the transformer, tubes and knobs was included for the princely sum of $80. That investment has paid large dividends where my other '901s are concerned...

This afternoon, the spare XTAL and VCO assemblies were relieved of all components which were necessary to populate the 'good' boards. I managed to get everything added to the XTAL board today and modded the WWV spot on the VCO board to tune its intended lower frequency.

I'm hoping to finish the VCO assembly by this weekend. One more step of the conversion procedure has me stumped for the moment: Changing a transformer on the Trimmer A board to a slug-tuned inductor. I'm following the instructions from an old Inrad kit and it calls out an L002-0545, on which I cannot seem to find a cross reference. A query was posted to the FT-901 Group inquiring as to the value (and the necessity?) of this part.

If all else fails I may have a go at engineering a suitable solution. Regardless, I'm going to have to rewire portions of the trimmer and band-switch circuits to enable the new bands to transmit. The counter assembly must also be modified to read the band-data MSD values properly.

N2NH
10-01-2009, 10:58 PM
That is a beautiful beastie! Someday I got to get a classic rig. Besides the SB-104A and HW-8. ;)
Those are neat rigs in and of themselves. How about a hardware hack for the HW8 which converts it to 160-30-17-12 or 30-17-12-10? Or puts two of them (one converted) in the same largish enclosure and gives you 8 bands..a common CMOS keyer, metering circuits and possibly a PA?

I have two, and while electrically excellent they leave a bit to be desired...cosmetics-wise. Thus, they might be good candidates for use in a projust such as this.

Thanks. So far the HW-8 is taking a backseat to the HW-9 (One has WARC Band Pack installed, the other was supposed to but didn't). Eventually I might convert it so it runs 15-20-30-40 or 10-12-17-30.

Right now I'm planning on adding PL to an old 10 M AZDEN if I can find a schematic for it. 10FM is dead for about 2/3rds of the cycle and yet it makes for good local comms up to 100 miles or so away with the right set up.

I'm also looking into ways to get my VX-8 to hook up to D-Star and WIRES as one of the local repeaters is starting to experiment with some of these modes too.

N8YX
10-02-2009, 04:58 AM
Right now I'm planning on adding PL to an old 10 M AZDEN if I can find a schematic for it. 10FM is dead for about 2/3rds of the cycle and yet it makes for good local comms up to 100 miles or so away with the right set up.

I'm also looking into ways to get my VX-8 to hook up to D-Star and WIRES as one of the local repeaters is starting to experiment with some of these modes too.
Azden -

Was that the PCS-4800, or the -7800?

N8YX
10-02-2009, 07:25 AM
Here's a schematic link - http://www.vintagemanuals.com/manual.php?manufacturer=Azden&model=PCS-4800

Owner's - http://www.hamradiomanuals.com/view_manual.php?m=25

A list of 'free' resources which may be of help - http://www.mods.dk/manual.php?brand=azden

N2NH
10-02-2009, 12:45 PM
Right now I'm planning on adding PL to an old 10 M AZDEN if I can find a schematic for it. 10FM is dead for about 2/3rds of the cycle and yet it makes for good local comms up to 100 miles or so away with the right set up.

I'm also looking into ways to get my VX-8 to hook up to D-Star and WIRES as one of the local repeaters is starting to experiment with some of these modes too.
Azden -

Was that the PCS-4800, or the -7800?

It's the PCS-2800. I believe it runs 25 W which is more than my Alinco at 10 W. I mean, it's ham radio. 10 Watts??

N8YX
10-03-2009, 02:58 PM
It's the PCS-2800. I believe it runs 25 W which is more than my Alinco at 10 W. I mean, it's ham radio. 10 Watts??
Isn't the -2800 a 2M rig?

N8YX
10-03-2009, 03:25 PM
We got WARC.

I am usually not given to overly utilizing profanity on a forum but I'm going to make an exception here:

What a fucking pain in the ass! :wall:

Thursday afternoon and part of Friday evening was spent scavenging a handful of resistors, capacitors, inductors, FETs, varicaps and other parts from a couple of spare boards, then populating the "good" XTAL and VCO boards. That done, the boards were placed back in the rig, which was then powered up and the new bands tested. 10MHz...check. 24.5MHz...nothing. Flashing "34.5xx" display indicated an out-of-lock condition. Danced around with the schematic - kept putting 'DSG off on dinner promises - finally went out for chow then back at the rig for a bit after we returned.

This morning I dragged the Tek 468 out and started having a look at things. XTAL board was outputting all the correct signals but the VCO wasn't. Start by changing a resistor to a jumper, as called for on Jean-Pierre (ON4AEF's) prints...nope. Next: Perhaps the 2SK19 I salvaged is bad? Replaced...problem fixed. We now have lock, and can receive the rig's marker signals.

On to the counter...

As delivered by Yaesu, the counter setup had WWV hard-wired to indicate "15.0xx.x" in the MSD bank. This needed to be changed to "10.0xx.x". Also, the 'Aux' band segment needed some diode steering to enable it to read "24.5xx.x", thus correctly indicating frequencies in the 12M band. Fortunately, a number of conversion articles (including Jean-Pierre's) exist on the 'Net. Three diodes, three resistors, a transistor and some wire later, we're ready to fire the counter up...

...except that it doesn't count now.

What The Fuck... :wall:

I spent the next hour undoing what I did...still no counter; shows "16.000.0". Got the scope out; checked the VFO injection and counter-mixer oscillators...all look good. Checked the MM5564 decade counter (timebase) output - no signal.

Fuck. Unobtainium.

On a hunch, I unsoldered the 655.36 KHz timebase crystal from both '901 counters and swapped them...turned the WARCed unit on...lo and behold, it works. Spent the next half hour adding the WARC-band "logic switching" components back in...all is in proper order.

Bad crystal. Whoda thunk it?

I now have one good counter (in my "project" rig) and a bad one in my main station rig. Need to find another crystal... :roll:

Meanwhile - I gotta bundle all this stuff up and clean my workbench off. The WARCed rig requires a complete alignment and I'm still waiting on a few parts to finish it.

N2NH
10-03-2009, 06:01 PM
It's the PCS-2800. I believe it runs 25 W which is more than my Alinco at 10 W. I mean, it's ham radio. 10 Watts??
Isn't the -2800 a 2M rig?

Nope. Just checked the front panel. 10 Meters. Man I'm glad I got that. When the bands open they'd want $75 for that old rig rather than the $15 I got it for a few years back. Just add PL and ready to go. Got an old CommSpec Box with 64 tones - not made anymore but great for any rig without tones.

The PCS-2000 is 2M.

N8YX
10-03-2009, 06:19 PM
Nope. Just checked the front panel. 10 Meters. Man I'm glad I got that. When the bands open they'd want $75 for that old rig rather than the $15 I got it for a few years back. Just add PL and ready to go. Got an old CommSpec Box with 64 tones - not made anymore but great for any rig without tones.

The PCS-2000 is 2M.
Vintage Manuals has what you want. IIRC, Azden's IF stages are pretty much the same between the various rigs in a series...thus, you may be able to identify the injection point via the schematic from a -2000.

N8YX
10-13-2009, 09:32 AM
Giving this thread a nudge:

Going to trod a bit of uncharted territory with the 90x in that there seems to be a dearth of AM modifications for the rigs. A check of AMFone.net shows several threads where people are wondering the same thing as I: How to make a 901/902 sound really good on AM?

Part of the answer lies in the audio board. There is an FT-102 AM mod which - upon examination - sees most of the interstage coupling and bypass caps increased in size by a fairly decent amount in some cases. Other caps are removed entirely.

The rest looks to be associated with the carrier board; that's where the bulk of the mic amp circuitry is located. One wonders what can be gained by some reconfiguration of that circuit...

N8YX
10-14-2009, 05:16 PM
Well, shi(f)t...fired the first of the two 901s up on AM tonight and have a pronounced hum on the carrier. Time to re-cap the power supply ... :evil:

AF6LJ
10-14-2009, 06:43 PM
Well, shi(f)t...fired the first of the two 901s up on AM tonight and have a pronounced hum on the carrier. Time to re-cap the power supply ... :evil:
Well that is a bummer, thankfully it's something straight forward.

N8YX
10-16-2009, 07:52 AM
Caps ordered.

I have been chasing a replacement counter timebase crystal for the past few weeks...finally got the specs and got in touch with ICM.

$109 per rock ??!!?? Wholly fsck! :shock:

Came across a deal on another '901 (with a bad counter crystal, of course..) for a price that was too good to pass up. I don't mind dropping that kind of mazoola into a component that'll give me a fully functioning, cosmetically excellent piece of gear...but...what of "Rig number two" that I have been fighting to bring back to life? There's no way I want to spend that kind of coin on a rig which I'm now planning on selling.

As I prowled the 'Net, looking for data on the MSM5564 - the clock/divider chip used as the counter timebase - I made an interesting discovery: Yaesu used the same part in their YC601 external display, and THAT design uses a 1.31072 MHz crystal. Hmmm... :chin:

Studying the circuits and looking for differences, one finds that the clock output in the 901's counter (with a 655.36 KHz rock) is at Pin 12 of the '5564...and with the YC601, it's on Pin 11. (This for a 5hz output.) Looking around for the 1MHz part on the 'Net revealed nothing...but Surplus Sales has 2.62144 MHz HC-6/U rocks available for the lofty sum of $4 each.

Further studying of the circuit indicates that I may be able to pick the desired clock signal off Pin 10, which is another 2x "down the chain".

I've got a spare counter to play with, and as a test I put a 3.6 MHz rock in it to see it the timebase chip would overheat while being clocked that fast. Nope...so this looks doable.

A little rework with a Dremel on top and bottom of board and a bit of wrapping-wire jumpering ought to give me a useable counter when (hopefully) the new 2.6 MHz rocks arrive.

N8YX
10-18-2009, 11:46 AM
'901 Number Tres is now sitting on my workbench.

Good News: Crystal in counter wasn't bad after all.

Bad News: It looks as if there's a problem with the counter mixer circuit - an SN76514 - and a lifted trace under the IC! Desoldering this is going to be a PITA. Anyone have a spare IC or two of this type?

The spare counter I have also has issues of its own: Namely, it appears as if the coupling caps between the heterodyne oscillators and the input to the mixer chip may be bad, as the counter won't stabilize...and there appears to be a goodly amount of distortion on the heterodyne signal waveform at the input to the mixer. At the oscillator, the signal looks good. I'm thinking this distortion is introducing some unwanted products up the line and results in a dirty counter-mixer signal, one which cannot be gated properly.

N8YX
10-18-2009, 02:01 PM
Swapped the caps; problem fixed - kinda.

Re-soldered the decade counters and ULN2004 display latch. Problem fixed. :yes:

Now I can get back to WARCin' this party ... :monkeydance:

N8YX
10-21-2009, 06:52 AM
There is a mod which must be done to the counter board assembly to get it to read correctly on the WARC bands; on 12 and 17M it involves adding a few 1N4148 or similar diodes to the MLY08 diode-matrix IC. Last night I modded one of my counter assemblies so it displays the 18MHz segment correctly when the bandswitch is tuned to the WWV/JJY position.

Power-supply electrolytics were next. I decided to tackle the harder of the cap replacement procedures - the HV filters - and swapped them for a fresh pair of 150uF, 500V units. There were a few snags encountered along the way - Yaesu's HV filter board is a multilayer affair and the new capacitor leads weren't quite long enough to make it through both. I had to add an extension at each capacitor lead so all the boards could be soldered together. In the process of fitting the HV rectifier board to the capacitor stack, I managed to crack a corner off the thing ... :wall:

Copious amounts of solder fixed it but should I ever need to extract the assembly in the future, the HV board will be repaired with a good dose of epoxy glue before it's put back in the radio. Should be fine, though - a couple of screws secure the broken area to a mating board, thus adding rigidity.

If all else fails I can get a replacement PCB from one of the eBay parts dealers or I can etch my own.

After reassembly, HV checked out on a multimeter at ~900v no load. Did not check the HV on a 'scope; should be smoooottthhh, however.

Rectifier "A" and "C"-board cap exchanges are next. A previous owner of one of the 901s I have was nice enough(?) to include a bag of goodies in the form of an assortment of replacement electrolytics and while I have the boards out I'm going to bring them up to latest Yaesu spec - key-click mods and all.

N8YX
10-21-2009, 08:53 PM
Rectifier "A" and "C" boards re-capped and modded this evening: Key-click, bias-loss prevention and anti-flashover circuit (protects against supply destruction due to runaway current draw in gassy tubes). There were several resistors which were cracked or overheated; they too were replaced.

I now have to sit down and make a parts list for the other two rigs plus the spare Rect "A" and "C" boards kept in my stash of hot-swaps.

Tomorrow night I'll hopefully get to mod the carrier, RF and NB/Processor boards along with the Processor Level control. After this I'm ready to dive underneath the chassis and make the rig transmit on its new band allocations.

Should be taking pictures of all this but my workbench is a disaster area. :roll:

AF6LJ
10-21-2009, 10:09 PM
Having a messy bench shows that something is being accomplished.

I hate it when things break while you are trying to rework them.
When I replaced the resistors on the HV board on my 820 I mounted them off the board by 3/16" this way the next time they go phut the HV board will be scared less. :)

N8YX
10-21-2009, 10:36 PM
When I replaced the resistors on the HV board on my 820 I mounted them off the board by 3/16" this way the next time they go phut the HV board will be scared less. :)
Flameproof versions will help in that regard.

I've got ten gazillion surplus caps here courtesy of a manufacturer switchover from leaded to SMT parts and I'll bet ya that I have exactly none of the values I need for this. :-|

AF6LJ
10-22-2009, 08:18 AM
When I replaced the resistors on the HV board on my 820 I mounted them off the board by 3/16" this way the next time they go phut the HV board will be scared less. :)
Flameproof versions will help in that regard.

I've got ten gazillion surplus caps here courtesy of a manufacturer switchover from leaded to SMT parts and I'll bet ya that I have exactly none of the values I need for this. :-|

The resistors I installed are flameproof, that board has been cooked a couple a three times from the looks of it.

I have noticed that whenever I buy a quantity of parts surplus I almost always end not being able to use 70% unless I want to series/ parallel them to get some value.

Lately the main problem has been just trying to find things.
Radio Shack use to carry the exact replacment lamp for the meter in my IC-745, they don't anymore the one they carry won't fit into the rubber receiver. Meanwhile in the back of my mind I can remember buying three of these replacment bulbs for something else about 20 years ago. It bugged me for about a day, and I decided I would sleep on it. I woke up Tuesday morning with an image in my mind where the box was that had the box of parts in it that I had stored here before I left for Texas. I walked out into the garage pulled the box down from the rafters and pulled out the box with parts I had purchased from several sources and there were two of those lamps and the preferred 10 ohm limiting resistors. :)

N8YX
10-22-2009, 09:11 AM
Radio Shack use to carry the exact replacment lamp for the meter in my IC-745, they don't anymore the one they carry won't fit into the rubber receiver. Meanwhile in the back of my mind I can remember buying three of these replacment bulbs for something else about 20 years ago. It bugged me for about a day, and I decided I would sleep on it. I woke up Tuesday morning with an image in my mind where the box was that had the box of parts in it that I had stored here before I left for Texas. I walked out into the garage pulled the box down from the rafters and pulled out the box with parts I had purchased from several sources and there were two of those lamps and the preferred 10 ohm limiting resistors. :)
If it's the one I'm thinking of...Chicago Miniature Lamp makes a 14v, 40,000-hr leaded bulb which will fit the grommets. I buy them 100 at a time and am almost through my last batch; time to order more.

FWIW: I can get 100 14v "Lamp w/ flying leads" already in said grommets for $80. 10 weeks lead time. If I buy a bunch, I'll make some available to anyone who's interested for cost plus shipping. These are exactly what Kenwood uses in their hybrid rigs.

Managed to grab a 901/902 memory module off Fleabay last evening for around $30. That goes in Rig #2, which didn't have one. Now I'm on the fence with Rig #3: It has a CW filter; no AM filter. Do I

1) add an AM filter, remove the CW filter, add a narrow SSB filter to the CW filter spot and modify the board so it'll give a "wide/narrow" SSB filter option then use the rig primarily on AM/SSB/FM

2) Leave the CW filter in place, add a narrow SSB filter to the AM filter spot and modify the board so it'll give a "wide/narrow" SSB filter option then use the rig primarily on CW/SSB/FM

?

It's going to be a backup to the other two rigs regardless...and the AM/narrow SSB filters are the same price at Inrad. :think

N8YX
10-24-2009, 01:47 PM
5 hours to solder 5 bandswitch wafer taps and a new plate blocking capacitor into place...now comes the function testing and realignment. I've only got to do this to two more rigs...joy... :roll:

AF6LJ
10-24-2009, 01:51 PM
Can't really tell you how I would configure the radios as far as filters go...

Good luck with testing and alignment.
:)

N8YX
10-24-2009, 03:12 PM
Can't really tell you how I would configure the radios as far as filters go...

Good luck with testing and alignment.
:)
There WAS smoke. :wall:

Seems a stray piece of very fine wire managed to get itself in between the bandswitch wafers, ground and the screen grid terminal. Took a wirewound on the Rect A board out; fortunately, I have spares. Just set the PA bias. Back into it I go...

AF6LJ
10-24-2009, 04:26 PM
Can't really tell you how I would configure the radios as far as filters go...

Good luck with testing and alignment.
:)
There WAS smoke. :wall:

Seems a stray piece of very fine wire managed to get itself in between the bandswitch wafers, ground and the screen grid terminal. Took a wirewound on the Rect A board out; fortunately, I have spares. Just set the PA bias. Back into it I go...
Well that Sucks, Glad you were able to rectify the problem in a timely manner.
:)

N8YX
10-24-2009, 08:54 PM
We got power...on all the bands, including the new additions.

BUT - only about 75w CW on 40 with 200ma IP :-|

Since the "max" occurs with the loading capacitor fully unmeshed...I'm wondering if one of the switched-in tank circuit padder capacitors has drifted in value. At 100w out, IP is 225-240ma; indicative of high circulating current... :wall

AF6LJ
10-24-2009, 09:06 PM
We got power...on all the bands, including the new additions.

BUT - only about 75w CW on 40 with 200ma IP :-|

Since the "max" occurs with the loading capacitor fully unmeshed...I'm wondering if one of the switched-in tank circuit padder capacitors has drifted in value. At 100w out, IP is 225-240ma; indicative of high circulating current... :wall
It might have opened up, Those mica suitecase caps go bad if they get a little moisture in them.
That's cool; every other band works :clap: :dance: :D

N8YX
10-25-2009, 10:08 AM
I've been poking through a few threads on the FT901 Reflector at Yahoo and have noticed that a number of other people have run into the same thing...and it boils down to a matter of alignment. I also noticed that 225-250ma IP is considered "normal" at max loading on CW. That being the case, the radio is doing exactly what it's spec'd at on 40M.

I typically run my tube rigs at around 75-85% of max power on CW, so it appears that at 200ma IP I'm good to go.

Kenwood specifies a loaded IP of 200ma in their hybrids, and I can see 100w out from my 820s on all bands with that much plate current. Interesting. I wonder if Yaesu's HV supply isn't as stiff under load as the Kenwood. :chin:

Things which I highly recommend any FT90x owner do are the Rect "A"/"C"-board, RF board and speech processor mods. With the latter and with the processor engaged, the 90x's audio sounds positively bitchin'.

There's a mod for the Carrier Board which replaces the ring-mixer diodes (1S1007) with a matched quad of hot-carrier parts. I hand-matched enough 1N5711s to do two boards and have several dozen more, so I'm going to convert all of the boards I have on hand to use these devices.

(The TR7/R7 setups I have on hand are going to get this mod as well but that's a project for later.)

Need to order more capacitors in order to rework the rectifier boards in the other two rigs, plus the "spares".

AF6LJ
10-25-2009, 10:33 AM
I've been poking through a few threads on the FT901 Reflector at Yahoo and have noticed that a number of other people have run into the same thing...and it boils down to a matter of alignment. I also noticed that 225-250ma IP is considered "normal" at max loading on CW. That being the case, the radio is doing exactly what it's spec'd at on 40M.

I typically run my tube rigs at around 75-85% of max power on CW, so it appears that at 200ma IP I'm good to go.

Kenwood specifies a loaded IP of 200ma in their hybrids, and I can see 100w out from my 820s on all bands with that much plate current. Interesting. I wonder if Yaesu's HV supply isn't as stiff under load as the Kenwood. :chin:

Things which I highly recommend any FT90x owner do are the Rect "A"/"C"-board, RF board and speech processor mods. With the latter and with the processor engaged, the 90x's audio sounds positively bitchin'.

There's a mod for the Carrier Board which replaces the ring-mixer diodes (1S1007) with a matched quad of hot-carrier parts. I hand-matched enough 1N5711s to do two boards and have several dozen more, so I'm going to convert all of the boards I have on hand to use these devices.

(The TR7/R7 setups I have on hand are going to get this mod as well but that's a project for later.)

Need to order more capacitors in order to rework the rectifier boards in the other two rigs, plus the "spares".

Sounds really good :)
I am going to do the diode mod to the balanced mod in my 820.
I take you matched the doides for closest forward resistance.

The 745 uses an IC balanced mod, and seems to work okay allthough I get better carrier suppression out of the 820, using the IC-756 as a bench receiver.

In regard to AM'ing the 745, I need to investigate the ALC circuit in order to find a way of keeping it from reacting to the AM signal. My 756 sounds good on AM but has a fair amount of negitive carrier shift, and the scope pattern looks processed when I feel it shouldn't. I want to avoid this when I do the 745 AM mod. What I would like to do and what I end up doing are two different things. I would really love to high level modulate the 745, but unless I want an outboard modulator or wish to deal with the headaches of class E or one of the variants, I'll have to settle for low level modulation.

I would love to build a 500W AM high level modulated all solid state transmitter. Class A modulator DC coupled all the way back to the input. :) :dance:

Speaking of which My FRG-7 is going to be relegated to Bench receiver duties. The "Frog" a little TLC, time to re-cap the power supply and audio. The first LO is a little more drifty on warm up than I would like, that might be fixable. The VFO is a real peace of crap, it is reasonably stable as long as the radio doesn't catch a breeze the circuit is not inclosed in a shielded compartment.
The whole design is a kluge, what is surprising is the darn thing works fairly well.

N8YX
10-25-2009, 11:16 AM
Sounds really good :)
I am going to do the diode mod to the balanced mod in my 820.
I take you matched the doides for closest forward resistance.
Yep. My friend Steve has a couple of semiconductor analyzers; one surplus...and one of them should be making its way over here soon. I'll be able to perform much a finer degree of current matching with the equipment.


The 745 uses an IC balanced mod, and seems to work okay allthough I get better carrier suppression out of the 820, using the IC-756 as a bench receiver.
I haven't measured it with a spectrum analyzer but I'm going to guess the first 901 (w/ hot-carrier BM) is around -50dB or thereabouts. The service manual specs it at -40dB when correctly adjusted, and others who have performed the mod have stated that it removed an equivalent amount of garbage from their transmitted signals.


In regard to AM'ing the 745, I need to investigate the ALC circuit in order to find a way of keeping it from reacting to the AM signal. My 756 sounds good on AM but has a fair amount of negitive carrier shift, and the scope pattern looks processed when I feel it shouldn't. I want to avoid this when I do the 745 AM mod. What I would like to do and what I end up doing are two different things. I would really love to high level modulate the 745, but unless I want an outboard modulator or wish to deal with the headaches of class E or one of the variants, I'll have to settle for low level modulation.
Search around for info on the TS-440S and modding it for AM. Basically...you need to adjust the ALC for minimal effect on all modes, or alter the circuit so the ALC threshold is changed when transmitting that mode. This is necessary with the -440S...talk about a dirty signal when in ALC compression! To think that Kenwood's engineering department hit multiple home runs with their hybrid line, only to completely and repetitively screw the pooch with everything since is somewhat disheartening.


Speaking of which My FRG-7 is going to be relegated to Bench receiver duties. The "Frog" a little TLC, time to re-cap the power supply and audio. The first LO is a little more drifty on warm up than I would like, that might be fixable. The VFO is a real peace of crap, it is reasonably stable as long as the radio doesn't catch a breeze the circuit is not inclosed in a shielded compartment.
The whole design is a kluge, what is surprising is the darn thing works fairly well.
I had one of those for a while. Not a bad receiver for what it is, but it's not the equivalent of an R7. Or an R5000, though some opine the synthesizer design is "noisy". Funny, but mine are pretty quiet. Shielding and cable routing goes a long way there.

One of the things I was going to do is to change some of the filters in the Frog. As it stands, I got a handful of assorted 455KHz AM filters on the cheap - which are at this point looking for a place to go.

N8YX
10-29-2009, 08:01 PM
Got a big box of capacitors and resistors in the mail from Mouser today - enough to rebuild both of the rectifier boards in the other two radios, plus my "spare" set. I know what I'll be doing Saturday...

N8YX
10-31-2009, 06:31 PM
Spent the morning replacing caps on several of the Rectifier boards...modding them for key-click suppression...and chasing down the diodes I needed at our local Radio Shark.

Yes, there's a hamfest tomorrow. Yes, I probably could have gotten them there, but I've got to winterize 'DSG's bike this weekend. It was raining here today so I did the boards instead.

N4VGB
11-01-2009, 01:04 PM
Search around for info on the TS-440S and modding it for AM.



Properly adjusted, the TS-440S is a pretty good AM rig right out of the box. An old friend of mine who lived a long time could no longer handle the rigors of keeping his old gear ship shape. He sold all the big stuff and replaced it with a TS-440S and linear combo. None could tell the difference on air between his former xmitter and the new rig. His old rig was a Collins 20V-2 AM broadcast xmitter. ;)

N8YX
11-01-2009, 01:12 PM
Search around for info on the TS-440S and modding it for AM.



Properly adjusted, the TS-440S is a pretty good AM rig right out of the box.
If (and this is a BIG "IF") the rig's ALC set point is dialed back and the stock Murata 455KHz AM filter replaced with the one used in an R-2000.

I have a '440S in my lineup. I know what a completely 'stock' one sounds like on the air (and looks like on a 'scope) and I'm not overly eager to operate the rig in AM TX as it was delivered from Kenwood.

N4VGB
11-02-2009, 05:50 PM
Search around for info on the TS-440S and modding it for AM.



Properly adjusted, the TS-440S is a pretty good AM rig right out of the box.
If (and this is a BIG "IF") the rig's ALC set point is dialed back and the stock Murata 455KHz AM filter replaced with the one used in an R-2000.

I have a '440S in my lineup. I know what a completely 'stock' one sounds like on the air (and looks like on a 'scope) and I'm not overly eager to operate the rig in AM TX as it was delivered from Kenwood.

Being an old time broadcast engineer, my old friend had quite the professioanl test gear setup. His 440 was very clean on a two tone test with a spectrum analyzer and produced perfectly shaped trapezoid patterns on his scope, sounded great on the air. He used an Amp Supply LK800C linear with 3 Eimac 3CX800A7 tubes, plenty of reserve power, so very little distortion added.

AF6LJ
11-02-2009, 07:47 PM
Good sounding AM is a pleasure to listen to.

N4VGB
11-03-2009, 09:49 PM
Good sounding AM is a pleasure to listen to.

On a quiet band with a single conversion receiver having no filters, it's amazing.

AF6LJ
11-03-2009, 10:13 PM
Good sounding AM is a pleasure to listen to.

On a quiet band with a single conversion receiver having no filters, it's amazing.
That really makes me want to find an elegant way do make the 820 receive AM. It's the only single conversion receiver I currently own.
.....
Come to think of it I have an idea or two...

N8YX
11-04-2009, 06:41 PM
That really makes me want to find an elegant way do make the 820 receive AM. It's the only single conversion receiver I currently own.
.....
Come to think of it I have an idea or two...
Hint:

Find an R-820 and set them up for transceive... ;)

AF6LJ
11-04-2009, 07:23 PM
That really makes me want to find an elegant way do make the 820 receive AM. It's the only single conversion receiver I currently own.
.....
Come to think of it I have an idea or two...
Hint:

Find an R-820 and set them up for transceive... ;)
That would probibly be a better approach.
What I would like to do is get away from the whole PLL business
I'd love to have a R-599, yah I know so would just about everyone else who has ever used one.

N8YX
11-11-2009, 11:37 PM
A bit of follow-up on two particular FT-901 Eham reviews:


Not a bad radio....the receive could be a little more sensitive, it does drift an unusual amount for a radio like that, and it does not have general coverage receive...it's okay.


Worst radio I have ever seen....terrible, drifty, all over the place, overdriven audio.....terrible.

Pass me some of whatever it is this guy was smoking when that verbiage was posted.

I have had one of mine sitting on 14.300.0 for the past two weeks (under VFO control, yet) and in that entire time it has not drifted at all. Zip, zero...you get the idea.

Additionally, it'll easily hear a 0.1uV signal out of the generator in SSB/CW modes, even on 10M.

Methinks these WonderHams need to quit evaluating hacked-up, CB-fied examples of a piece of gear...especially if they lack the skills or knowledge to discern a correctly functioning model from one that isn't.

N8YX
12-28-2009, 09:15 PM
FT-901 #2 finished.

In addition to the 'factory' bands, it now covers 30 and 12M. I reconfigured the WWV spot for 10MHz and added 24MHz to the "AUX" spot.

The easiest way to mod one of these rigs is to find a junker FT-90x and lift any required parts from it. In the case of a '902, one can directly salvage and substitute the crystal oscillator components, including those for the "missing" (unmarked) AUX band position. One can also use parts from a junked FT-901, but you'll have to order the required crystals.

The short "how to" list:

1) Remove XTAL and VCO assemblies from radio
2) Add and/or replace components at the WWV and "AUX" spots in each assembly. Pay close attention to the type of slug-tuned inductors, padder capacitors and bias resistors used for each band segment. You can work from a '902 schematic if unsure of which parts to use, or consult the WARC-conversion articles which can be found 'round the Internet.
3) Replace XTAL, VCO assemblies
4) Remove counter assembly from radio. Depending on which band(s) you're adding, you'll need to do a little hardware reprogramming of the counter's display programming matrix. Again, there are several articles available which explain the ins and outs. There is also a "secret" display programming line; an in-depth description of counter programming is found elsewhere in this writeup.
5) After counter has been tested, install it in rig.
6) Align new XTAL/VCO tuned inductors per Yaesu's service manual. Ensure that the PLL locks all the way across each new band's tuning range.
7) Invert radio and remove two shielding plates from the PA and Trimmer A/B/C areas.
8 ) Rewire band switch segments S1E, S1G and S1I to enable receive and transmit preselector peaking. This involves running jumpers from the "WWV" and "AUX" switch contacts to the 10, 15 or 20M contacts...depending on what combination you've elected to add. There is a gray wire which runs from one side of L09 (a chassis-mount, slug-tuned inductor) to the WWV position of S1I. This should be removed when you jumper the WWV contact to the 20M contact on the same wafer.
9) S1R is the PA screen-grid voltage selector switch. Jumper the "WWV" and "AUX" positions to the rest of the contacts if you want to transmit on both spots; omit one or the other if you don't. More on this in a bit.
10) S1O is the PA tank coil switching deck. You'll need to add wires from the unused WWV/AUX contacts to the PA tank coil (a toroid) or jumper them to the nearest band segment. This is dependent on the new bands to be added.
11) Remove upper PA shield and tubes. Remove PA input circuit board and locate C01, a 100pF, 1KV rectangular mica capacitor. Remove it and replace with a 100pF, 1KV (or better) silver-mica unit. The OEM part has been known to fail shorted and will allow screen voltage to get into the rest of the radio...
12) Replace all items removed in Step 11.
13) Align the rig per Yaesu's service manual. Watch yer a$$....there's high voltage on the trimmer boards.
14) Replace all covers.

Correspondence with Jean, ON4AEF led me to a modification article he authored...and which contains the following:


"The WWV position is wired for receive only and the cached AUX( 11 M) band position is standardly full wired for TRX."


"Due the fact the AUX(11 M) bandswitch position is originally fully wired for transmit and receive, we do nothing here."

That's true of a Euro-spec '901 but not one bound for the States. I recently got hold of a counter assembly from a European FT-901 and the "Aux" position was wired by the factory to indicate 27.xxx.x MHz! :shock:

Connecting Pin 2 of Q2910 to the "Aux" band switch counter input pin enables the readout; it's the only "vacant" pin on a U.S.-spec '901. Evidently, Yaesu "built" this logic into the counter programming matrix on purpose. You'll need to change this line's programming if you wish to use it for 12 or 17M. A couple of 1N4148 diodes to pins on Q2910 will do it. Tack the anodes to pins 1 and 6 for 17M; 5 and 14 for 12M. The cathodes are twisted together and soldered beforehand; their junction is tied to the counter's "Aux" input pin via a length of wire. Use heat-shrink tubing over the pin connection and over the diode junction.

30M programming is a bit more complicated. Jean's article provides a good explanation of what's needed.

By omitting the screen voltage connection on Wafer S1R for the 'Aux' spot, one can set this range up just to receive. This is similar in concept to what Yaesu did with the early FT-101 series with their marked "11M" band switch position.

All of the above is a moot point on the '902. IIRC, there's no easy way to "reprogram" its ASIC-based counter for frequency ranges other than those programmed in at assembly time. And since the rig already covers the WARC bands...