IC-745 Slowly Comming To Life

[AF6LJ]

This is a project I have been looking forward to for some time now. I have two ICOM IC-745s one in reasonable condition and one in very used condition. The one in very used condition I have owned for over 25 years. I bought it back when I was going to get my license the Third Time, it's relegated to being the hanger queen.

http://i558.photobucket.com/albums/ss21/AF6LJ/IC-745/745.jpg?t=1254237766

The above radio arrived in non working condition, which was the expected condition. The first order of business was to obtain a PIEXX memory module.
With the module installed troubleshooting could begin.
As one might guess the main PLL was unlocked, the sub loop functioned properly and since I had placed an earlier order with Mouser for my 820 I went ahead and ordered some trimmer caps for the four VCOs on both PLL boards. (this unit and the hanger queen.)

Both boards were powered up and some basic tests were conducted before installing the board back in the radio. All the VCOs could be adjusted and steered over the required frequency ranges. Each VCO covers 8MHZ of the total range of the PLL.

Upon troubleshooting the hanger queen's PLL board in the unit it was discovered that the PLL chip was bad.
All the correct serial data and control signals from the logic board were present, as well as the proper input signals from the main loop prescalier and reference divider. I ordered a PLL chip and prescalier chis from ICOM (OUCH) I should have bought the PLL chip from RF Parts.

The parts arrived and I proceeded to repair both boards. One board (the original board in the above radio) worked after replacing the trimmers and some adjustment of L8 (which is not documented in the service manual). L8 is the output transformer for the sub loop filter amplifier. The hanger queen PLL didn't work after repair and it was discovered that I had unsoldered a jumper wire that supplies power to the fourth VCO and the first buffer stage. The bottom shield was removed and the joint repaired. This board has yet to be tested. I may go ahead and test it after I deal with what is left to repair.

Bringing us up to date;
I have a numb and weak (outpur RF) 745 along with the usual dirty pots, switches, relays, and connectors.
As frequency increases both power and sensitivity decrease. This is acting like possible first mixer or first LO buffer (located on the RF board)
Receiver sensitivity is 20DB down.
Transmitter power (RTTY mode) starts out at 100W+ on 160M and ends up around 10W on 10M.
I can hear the low pass filters switching when bands are changed. There are a few other checks that need to be made before jumping to conclusions though.

I also have to investigate why the metering circuits are not functioning properly, but first the above issue needs rectification.

More to follow, I will have some time today to work on sensitivity / power problem.

[N8YX]

Good deal. Which trimmer caps did you go with? I'm go to have to re-cap a pair of R-71As sometime soon. :-?

[AF6LJ]

Good deal. Which trimmer caps did you go with? I'm go to have to re-cap a pair of R-71As sometime soon. :-?

http://www.mouser.com/Xicon/Passive-Components/Capacitors/Trimmer-Variable-Capacitors/_/N-5g94Z1z0zls8/

i went with XICON
2.8-12pf for the low freq. VCOs
1.8-6pf for the hi freq. VCOs.

http://www.mouser.com/catalog/specsheets/24aa.pdf

[AF6LJ]

Well this morning saw the failure of my desk lamp (a thrift store special) and the continuation of my PLL boards saga. The original PLL board has me scratching my head a little. VCO-1 & 2 work fine VCO three and four appear to be low in power output. With VCO-3 being the worse. I am wondering if i don't have a leaky switching diode or two, the transistors that turn on the VOCs work just fine and all they do is provide a DC return for the selected VCO. It might be time to pick up some IN5711's and replace them.

The second PLL board, the one from the hanger queen appears have a bad mixer, the one that mixes the up-converted sub-loop output with the VCO sample signal completing the main loop.

There are more tests I can do that will confirm this conclusion, however that involves more un-soldering and re-soldering of components than I really want to do at this time.

I'll just put in a parts order and wait and see regarding both boards.

This would be more fun if my desk lamp had not died this morning. :wall

[N8YX]

How's the Icom project coming?

[AF6LJ]

How's the Icom project coming?
I was busy today and haven't had time to get to my work table.
Tomorrow will bring more progress, I should have somrthing to report tomorrow evening. :)

[N8YX]

How's the Icom project coming?
I was busy today and haven't had time to get to my work table.
Tomorrow will bring more progress, I should have somrthing to report tomorrow evening. :)
Cool.

My table is now piled high with parts boxes - we started remodeling a spare bedroom/storage room and as a result, I lost my bench for a few days.

A spare counter for my other '901 is inbound and I've been working with Sara Gore of ICM (one of the Best People on Earth!) to get another timebase crystal for the failed counter unit.

I am half-tempted to design my own counter unit and do away with the OEM part altogether. Blue VFD graphics module as a readout....how cool would that be? :yes:

[AF6LJ]

How's the Icom project coming?
I was busy today and haven't had time to get to my work table.
Tomorrow will bring more progress, I should have somrthing to report tomorrow evening. :)
Cool.

My table is now piled high with parts boxes - we started remodeling a spare bedroom/storage room and as a result, I lost my bench for a few days.

A spare counter for my other '901 is inbound and I've been working with Sara Gore of ICM (one of the Best People on Earth!) to get another timebase crystal for the failed counter unit.

I am half-tempted to design my own counter unit and do away with the OEM part altogether. Blue VFD graphics module as a readout....how cool would that be? :yes:
I like that idea Blue graphics :)


I am going to have to fix my HP-5245 in the garage, the oven power supply went belly up. It's just a 24VDC power supply and all it needs are diodes and a fliter cap. I like those nixie tubes.

We have a fence to repair in a couple of weeks, now that it's cool and before it rains :rofl: :rofl:
Rain what is that :think

[N8YX]

We have a fence to repair in a couple of weeks, now that it's cool and before it rains :rofl: :rofl:
Rain what is that :think
Rain is what stopped me from winterizing another of my motorcycles this afternoon. We got two of them done and were getting ready to wash a third when the sprinkles started.

Nixies...remember the NCX-5? I had a friend who owned one of those.

[AF6LJ]

We have a fence to repair in a couple of weeks, now that it's cool and before it rains :rofl: :rofl:
Rain what is that :think
Rain is what stopped me from winterizing another of my motorcycles this afternoon. We got two of them done and were getting ready to wash a third when the sprinkles started.

Nixies...remember the NCX-5? I had a friend who owned one of those.
I've seen pictures of the NCX-5 I have never seen one in real life.
That was back when radios had personality, that was a sharp looking radio that and the NCL-2000 (which I have seen in real life)
Everything now is ether black, gray or silver.

[N8YX]

I've seen pictures of the NCX-5 I have never seen one in real life. That was back when radios had personality, that was a sharp looking radio that and the NCL-2000 (which I have seen in real life)
Everything now is ether black, gray or silver.
My friend Hank - ex-KA8RZT (SK) had the rig, a power supply and the external VFO.

I would love to lay my mitts on an SR-2000 and matching peripherals. Why? All the rigs I have deal with QRM/QRN a lot better than the Hallicrafters would, but there's just something about those old radios.

The game of 'What If?' is also fun to play: What If National had marketed a transmitter to match the HRO-500...

[WØTKX]

I would still like one of these silly messed up things, but John already knows that... :roll:

http://www.hamanuals.com/S1/Graphics/My-CX7B.JPG

[N8YX]

I would still like one of these silly messed up things, but John already knows that... :roll:

http://www.hamanuals.com/S1/Graphics/My-CX7B.JPG
Was made by a subsidiary of NCR.

The CX-11 is the better rig in the series, BTW.

[AF6LJ]

N8YX;
I agree with you about the old radios, I love the way they look and work.

WØTKX;
You and me both, that was touted at the ultimate radio back in the early 70s. For many it was the ultimate project radio :)

Almost ten years ahead of it's time, and nice looking to boot.

[WØTKX]

Was made by a subsidiary of NCR.

The CX-11 is the better rig in the series, BTW.

Long ago and far away when we actually talked on the air,

and some PM's...

I know you are a resource about these.

The SK's call that I have was one of the early "kit finishers" of the CX7a. He was pretty annoyed about what went on for a while, till he got the bugs ironed out. A constant stream of cuss words when he was working on it. :rofl:

And now, back to the IC-745, already in progress...

[N4VGB]

After all else is done, there's this little mod for the IC-745, http://amfone.net/Amforum/index.php?topic=7107.0;wap2

:mrgreen: Yep, it's a very good sounding AM transmitter also, after this mod. :mrgreen:

[N4VGB]

I would still like one of these silly messed up things, but John already knows that... :roll:

http://www.hamanuals.com/S1/Graphics/My-CX7B.JPG

Here's a horror story for you. At the very first Tri Cities hamfest in Gray, TN, many moons ago, I passed on a nice looking but dead on xmit Signal One CX7. It was cheap and probably a simple fix. :cry: At the table next to this find sat W2IQ/Hank with pics of K4FW/Al Kahn's Collins KW1 that he had left with Hank when he depated TN and had ordered Hank to sell on his behalf. I passed on that one also. :cry:

Several more Signal One CX7 and CX11 sets showed up at hamfests in this area after that first exposure and I found reason to pass on them all. Most had admitted problems but all were cheap. :cry:

The last Signal One that I saw for sale was the property of country music singer Ronnie Milsap/WB4KCG and was on eBay. I was out of the bidding on that one quickly, as the price soared. Supposedly Ronnie was the original owner and from the pics it looked brand new, described as 100% with all update mods.

Live and learn, as the old saying goes.

[N8YX]

I saw an -11 at Dayton this year. Guy wanted ~$5700 ...

[AF6LJ]

After all else is done, there's this little mod for the IC-745, http://amfone.net/Amforum/index.php?topic=7107.0;wap2

:mrgreen: Yep, it's a very good sounding AM transmitter also, after this mod. :mrgreen:
I saw that mod a few months back.
Not a bad hack, there are a few ways to do that mod.
I have another ideal in mind.

Well today I am going to borrow a couple of parts off one of the PLL boards to fix the other. We shall see what happens.
Up to this point I wanted to avoid doing that, but hay you only live once :)

[N4VGB]

I saw an -11 at Dayton this year. Guy wanted ~$5700 ...

I just took another look at the registry for the Signal One CX11 & CX11A, still looks like I know of 2 that are not on there, one of them could be the one on the registry listed as wishing to remain anonymous. The registry claims that only 111 of the CX11 and CX11A models were built, guess I was lucky to have encountered the ones that I saw at area hamfests. The registry only has 41 known units listed, it seems to be a rare bird indeed. Even at that level of rarity, $5700 seems a bit much. :shock:

[AF6LJ]

It's fixed;
I went ahead, took the easy way out and repiared the PLL board with decreasing output. I borrowed two transistors out of the VCO buffer on the other board and that fixed the problem.

Before cannibalizing the other board I made a few measurements which included checki9ng the switching network that coantrols the four VCOs. I was conserned that one of the switching doides may have been leaky, turns out that wasn't the case after looking for reverse leakage in the shut off VCOs.

I ended up replacing the muting transistor (used to kill the first LO when the PLL is out of lock) and the VCO buffer output transistor.

Reciever sensitivity is .3 microvolts (with the Pre Amp off) across the the radio's HF coverage, less below 1.7MHZ.

Now I have a whole boatload of aligment to do, and maybe some small repairs. The Power limiter needs adjusted, the radio does 110 watts on 29MHZ. (a little hot) I'll turn it down to 90W max no need for much more than that.

The power control is dirty and gave my power supply fits. :)

I'll let it run for the next two days and then begin alignment.

it was a hard decision to cannibalize the other board, but I decided it was time to stop messing around and fix the radio. That is way I have a hanger queen in the first place.

[N8YX]

There's another -745 on eBay at the moment; if the bidding stays reasonable, you may be able to get yourself another parts rig.

[AF6LJ]

Thanks for reminding me that it's time to look at my saved searches. :)

[N8YX]

Thanks for reminding me that it's time to look at my saved searches. :)
Did you snarch it while the snarching was good?

[AF6LJ]

Thanks for reminding me that it's time to look at my saved searches. :)
Did you snarch it while the snarching was good?

I had a watch on two of them and both went for more than I wanted to pay.

[AF6LJ]

http://i558.photobucket.com/albums/ss21/AF6LJ/IC-745/IMG_0574.jpg?t=1256306088


Well except for a few minor things I'm finished.
The receiver does a little better than .25 microvolt
I had to replace the meter lamp, it had burned out after I lifted the front panel for cleaning.
This receiver is quieter than the 756.

The speech processor needs a little touch up on the alignment. The mic amp is rather numb for some reason. The radio was easy to drive with an audio source I wonder if the mic voltage is low....
The audio sounds good on a monitor receiver and looks good on the scope.

The IC-756 is out of the picture for now, I need to try and track down some internally generated noise and see if I can do something about it. While I am at it I need to verify the alignment on the automatic antenna tuner, there are certain conditions under which it will kick itself out of line when it should be able to match the load. I don't think this radio is going to spend much time on the bench.

I'm going to have to come up with a better operating position, sooner or later the computer is going to end on the opposite side of the room.

[N8YX]

I'm going to have to come up with a better operating position, sooner or later the computer is going to end on the opposite side of the room.
Looks good. :agree:

On the subject of operating positions..."rickety" would best describe the old shack table incarnation. Its finest moment was an appointment with the trash collector. :shock:

Over the 2007-2008 winter I built a new one from an executive desk, an interior door whose width and thickness matched the desk's top, two 24" x 60" , two 24" x 84" doors as shelves...center and end supports scratchbuilt from 2x4 and 3/4" interior plywood, covered with walnut veneer. The large span is butted up to the desktop and is supported by a custom platform which incorporates two 2-drawer file cabinets and a center support, also of plywood, 2x4 and 2x6 construction.

The whole shebang was veneered and lovingly stained a dark walnut. There was probably $100 worth of stain used in the project. It was applied heavily enough that the equipment surfaces are effectively liquid proof.

Ground busses and power distribution facilities were built in, as was cable management.

The sad thing is that I could use at least three more of these arrangements, and a suitably sized room to house them. One of my FT901DMs, matching accessories and an FT726R occupy the bottom left areas. The large span holds two TS820S/R820 pairs and a third R820. Above them on the second shelf are all the Kenwood peripherals: TV502/506, AT200s, SP820s...SM220s and an AT230.

Top shelf has all of my scanners and computer-controllable HF/VHF gear. Right now, that consists of a TS440S/R5000 pair. A bunch of Drake MS7 speakers also reside there, for use with the scanners.

[AF6LJ]

Sounds like a good arrangment, I have been running some designs for an operating / work desk here based on using a couple of solid core door blanks. Right now the operating position is on the edge of my oak computer desk. (real wood even!)
The bookshelf that serves as shelves in my first pic is the usual plastic contact paper covered Beaver Poo Bord from China.

Sometime soon I need to fit in a few hours to build a directional coupler for that scope sitting on the extreme right to provide transmitter monitoring.

Used SB-610s and HO-10s are problematic due to the age of the transformers. A Kenwood SM-20 costs too much. I paid $25.00 for that scopa and it's a 100MHZ scope. It use to be my mainstay before I picked up my Tek 466.

[N8YX]

Sometime soon I need to fit in a few hours to build a directional coupler for that scope sitting on the extreme right to provide transmitter monitoring.
What kind of frequency range and power are you looking for? I may have just the thing you need in Ye Olde Junque-Box. IIRC, it's a Motorola line sampler and is good for at least 100w; possibly a kilowatt.

[AF6LJ]

100 - 500 watts up to 50MHZ.
It doesn't have to be calibrated.
I have made them before out of two peaces of coax.
I only want about -30-40DB of coupling.
Just take two peaces of coax,
remove the outer jacket from both,
tin the shield,
with a dremel tool or something simular cut a slot almost end to end lengthwise,
soldeer the two peaces togather with the slots facing,
Place the assembly between two peaces of plexyglass, or whatever for stability, put on connectors on and your done....
Oh don't forget to terminate the reflected port.

Quick, dirty, cheap, but effective. :)

You can make some darn good ones for UHF with little effort.

I have one of those Motorola gizmos around here someplace.

By the way before I forget,
When you get those lamps let me know I want ten of them.

[N8YX]

This sampler is made from aluminum - a machined body.

Acquired it by virtue of someone else's junk box...

[AF6LJ]

This sampler is made from aluminum - a machined body.

Acquired it by virtue of someone else's junk box...
Cool!
Sounds good.

What does it have on it for connectors??

[N8YX]

This sampler is made from aluminum - a machined body.

Acquired it by virtue of someone else's junk box...
Cool!
Sounds good.

What does it have on it for connectors??
SO239s at each end. The sampler outputs (there are two) appear to be feed-through capacitors.

[AF6LJ]

This sampler is made from aluminum - a machined body.

Acquired it by virtue of someone else's junk box...
Cool!
Sounds good.

What does it have on it for connectors??
SO239s at each end. The sampler outputs (there are two) appear to be feed-through capacitors.

I wonder if it's made to output RF or DC?

[N8YX]

This sampler is made from aluminum - a machined body.

Acquired it by virtue of someone else's junk box...
Cool!
Sounds good.

What does it have on it for connectors??
SO239s at each end. The sampler outputs (there are two) appear to be feed-through capacitors.

I wonder if it's made to output RF or DC?
One way to find out. I'll throw it inline and connect my 468 to the outputs. Might be useful for doing some out-of-lineup tuneups of the 901s, the first of which is nearing completion.

[N8YX]

Sue, have you been over on AMFone.net recently?

I think we had discussed the IC-745 AM mod which is described there...

Anyhoo - I was searching the site for a bit of info about how to make the '901 sound better on AM and I came across a very interesting mod for the TS-520. Basically, it involves using a dual-section relay to switch the mic amp output off the balanced modulator and onto the source of the RF PA predriver, itself a dual-gate MOSFET:

http://amfone.net/Amforum/index.php?topic=4903.0

That being said, I looked at my TS820S service manual and have come up with a way to do same.

My thoughts are to convert the 'Tune' position to 'AM TX'. Almost everything is set up properly in stock form; the exception being screen voltage. In 'Tune', there is 105v delivered to the PA screens via a voltage divider across the screen supply. It consists of a pair of 68K resistors. If one were to change the divider ratio to put, say, 130-150v on the screens, the max power output would remain in the "safe" region yet the operating class would be made more linear.

Rather than a single predriver transistor (a la 520), Kenwood used a pair in push-pull for the '820's RF amp chain. MOSFETs are used here, and I have a feeling that the same modulation technique could be successfully utilized.

Reception....is a whole 'nother ballgame. I'm lucky in that I'm planning to slave an R820 to the converted TS-820S, thus giving me true AM reception. Anyone else contemplating this conversion has a little work to do in the detector department.

Thoughts?

[AF6LJ]

That is essecially the line of thinking i was pursuing regarding AM in the 745. It's easy enough to set up to check out the concept.
I'm an implementation that is transformerless, using a series transistor to modulate the collector voltage in ether the driver or predriver. The Yesu FT-301 and countless CB radios use this technique with great success.

Ether way this is far more elegant, and should produce much better audio than the usual hacks. :)

As a side note;
Not sure how long I will continue to be here.
the inbreeders are getting on my nerves, and I have made my feelings about them quite clear.