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Old 14th Aug 2019, 11:37 pm   #21
SiriusHardware
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Default Re: Yaesu FT480R

With almost no idea what is going on but assuming all of the pins 1 through 18 are digital logic signals, I find it highly suspicious that pins 1 and 3 through to 18 are going up and down between expected logic levels but pin 2 is permanently stuck at an unchanging 2V.
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Old 15th Aug 2019, 5:59 am   #22
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Default Re: Yaesu FT480R

Highly suspicious.

A look with an oscilloscope would show if it was 2v DC or a logic waveform with an average of 2v, switching between 0 and 5v. Though I suspect 2v DC is the most likely.

This node needs checking for dirty connectors, muck on boards, bad connections (IC sockets?) and if nothing found it would point to failed IC. The glass passivation of this era of chips created a corrosion problem on the metal layer of the die if moisture crept into the package.

David
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Old 15th Aug 2019, 9:19 am   #23
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Default Re: Yaesu FT480R

I will work on that Chris and thanks for the effort to measure.

At first sight it looks OK but I will check through with a little more time.

The stuck at 2V Pin is RF In so not surprising it does not move - it will be 4MHz pulses looking like ~1/2 supply. Pin 17 RF Out you might expect likewise but you saw 0V. Could be very narrow pulses perhaps.

More later.
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Old 15th Aug 2019, 9:58 am   #24
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Default Re: Yaesu FT480R

If it's the RF input, then that doesn't look like a bad bias voltage.

David
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Old 15th Aug 2019, 10:25 am   #25
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Default Re: Yaesu FT480R

I have taken the binary and found the divide ratios for each step.
They make perfect sense provided that the main loop (10kHz one) is programmed to step between 145.528 and 145.529.

Doing that seems a little odd but who is to say what offsets are being taken out here - the designer had a free hand.
I'm pleased the table started with a division of 815 - see back at Post #7!!

To confirm it might be interesting to see what happens over the next 10kHz by repeating the exercise between 145.530 and 145.539 kHz. At least an abbreviated test to see if pins 7,8,9,&10 follow the same pattern would be interesting.

I think all this points to the uP and the 4094 shift registers being blameless. The trouble is almost certainly inside the works of TC9122, Q3005. It is not dividing by what it is being told.

It might be an idea to look into their availability.
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Old 15th Aug 2019, 6:51 pm   #26
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Default Re: Yaesu FT480R

Thanks Jon,
I will carry out the further tests and source a replacement TC 9122.
Thank you also David for you comments.
Will report results in due course.
Chris.
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Old 15th Aug 2019, 7:00 pm   #27
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Default Re: Yaesu FT480R

Good. It is a bit hard to find somewhere trustworthy to buy them - I have been looking.

They do turn up in scrap sets. Here is a VHF PMR handheld which contains one.
It is sort of based on the Icom IC2E design. A shame to scrap a set but if needs must.

I think David's theory is a good one. It seems happy to divide by 805-845 but does not like 855-895 - that becomes 805.
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Old 15th Aug 2019, 8:56 pm   #28
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Default Re: Yaesu FT480R

I have located a new TC9122P.
My trusty helper, Janet (XYL for 58 years) and I will measure the pin voltages tomorrow and post results.
The PDF file is interesting as it confirms the results as found so far.
73 Chris.
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Old 15th Aug 2019, 10:46 pm   #29
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Default Re: Yaesu FT480R

If we get desperate, I have an FT480 that's laid unused for 7 years. It worked fine when last under power, so I could extract voltages and waveforms from it for comparison.

David
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Old 16th Aug 2019, 4:34 pm   #30
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Default Re: Yaesu FT480R

Chris
I have serviced a few of these in the past. If I remember correctly (long time ago), there were some gates that were diode ORed. I had one or two with similar problem to yours and found these ORed gates with the Japanese diodes had developed a much larger voltage drop than around 0.7 normal to around 1.2v. This then ensured the logic was not getting the correct data.

As I said, it was a long time ago and I have no circuits now of the rig, but it might be worth checking the various diodes for forward voltage drop, I did replace them with IN4148s.

73
Andy G3UEQ
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Old 16th Aug 2019, 5:45 pm   #31
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Default Re: Yaesu FT480R

Update.
We have repeated the voltage test with the frequency set to 145.530 to 145.539 and the readings on pins 7,8,9 and 10 follow the same pattern as before.
I have removed the TC9122P and will fit the replacement as soon as it arrives. I may use a 18 pin socket to assist any further investigation.
Thank you Andy for your comments. I will look at the diodes when I have replaced the IC and report findings.
73 G4BYZ
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Old 16th Aug 2019, 6:23 pm   #32
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Default Re: Yaesu FT480R

Good that the pattern repeated but still strange that the 10kHz programming turns over at xxx.528!
The observations still support the divider is bad.

There are no diodes to give trouble here - see schematic snippet.

I think the socket should be OK since the TC9122 is only working at about 4MHz. I'm not sure I would go with it long term but for fault finding probably OK.
Make sure it is the turned pin type - the others cause more faults than they are worth!!
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Old Yesterday, 6:05 pm   #33
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Default Re: Yaesu FT480R

Hello Jon and others,
The plot thickens.
I have changed the TC9122 for a new one and the results are exactly the same as before. ie frequencies indicated ending in 4,5,6,7&8 are 5 KHz down on transmit. ie 145.525 transmits as 145.520, this is also the case on receive.
Any further suggestions would be very welcome.
I will have a look the diodes Andy, but am not sure where to start.
73 Chris G4BYZ
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Old Yesterday, 6:41 pm   #34
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Default Re: Yaesu FT480R

Arrgh - that is really strange! What can it be?
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Old Yesterday, 6:43 pm   #35
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Default Re: Yaesu FT480R

I think there's a satellite offset on that radio... could it have gone loopy?

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Old Today, 10:24 am   #36
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Default Re: Yaesu FT480R

Hello Chris - no flashes of inspiration so far but still thinking on it.
A couple of questions come to mind.

The TC9122 you removed was the original one installed by Yaesu? No signs it has been resoldered before and this set has worked fine in the past?

Is there any chance of a picture of the new and old TC9122s? I'm interested in case we can see anything with date code markings etc.

I was going to say are you sure you changed the right one since there are 2 used. That is a stupid question as it will be the one on which you measured the BCD codes 805,815 etc - forget I even thought of that but this fault is getting my goat - I'll grab at anything. It has to be in this section of the circuit somehow.
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Old Today, 5:50 pm   #37
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Default Re: Yaesu FT480R

Jon,
Thanks for your continued interest.
I will photograph the items although I did have to cut the original item pins out of the board.
There was no evidence that the original item had been replaced. I have had the radio for about a year and was unaware of the problem as it has not had much use and the frequencies used did not use the faulty digits.
Will send the information tomorrow.
Regards
Chris.
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Old Today, 6:03 pm   #38
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Default Re: Yaesu FT480R

OK pictures would be good.

Yes a fault like that can be something you don't notice straight away.
I had a TR2400 back in the 80s and any QSY made from calling channel to S21 lost the QSO. S22 was always fine. It was brand new and the stealer of the day wanted me to pay for return under warranty. I didn't think much of that and I had a Pye Telecom development lab full of gear at my disposal. Shorted pins on the uP.
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