FT-480R woes

[murphyv310]

Hi.
I've two FT-480R transceivers. One I got a couple of months ago, it started to sound distorted on SSB transmit and on FM it dropped in power after a minute or so.
Traced to the M57713 power module being intermittent. Before this issue I did note a fair bit of drift. I decided to do a full set up but noted there was a lot of drift on the PLL voltages. There is a lot of that glue around the crystals that had hardened and gone brittle and very dark. I softened it with solvent and gradually removed it, there was bad corrosion where it covered the crystals and components. A good clean up and the PLL Set up much better. A few days later then the PA failed.
So enter FT-480R number two. A bit off frequency, poor LF audio and a dull display.
C133, 1uf was dried out and this cured the audio response. C24 10uf 50v was also faulty and this cured the dull display, a pig to do though with double sided print
Then I decided to tackle the PLL. Oh what a mess. The 63.9151mhz crystal X3002 fell apart when the glue was removed, some of the nearby passives were shot too.
I've contacted Yaesu on the off-chance that one is available. So right now the first PLL board is in the second unit but I also see the frequency tracking is wrong so something else to investigate.
The plus side is some of the QSOs I've had via the Cork repeater, on the Tropospheric lift last night and today.

[murphyv310]

Hi.
I've been working on the second set today but not really any further forward.
I've put a wanted up for a 63.9151mhz crystal or the possibility of a PLL board.
If I get no luck I'll keep one for spares.

[Radio Wrangler]

There is the possbility of repairing the crystal....

If the quartz element and its plating is undamaged, it could be re-homed in another solder-sealed case from a sacrificial crystal.

I'v done this before, opening a failed crystal to re-solder a lead-out wire from crystal itself to pin and then soldering the case back together again. It was a channel setting crystal in a trio base station 2m transceiver belonging to Peter, GM3MUM. I used to get called in for things the local club couldn't fix. It was late on a Sunday, 25 miles from home and there was nothing to lose. Peter was in a Cheshire home and visits were special, very special. The guy keeping an eye on the door opened the Yale latch with his mouth. It put me in the mood for not giving in easily. The building had been the family home of Christian Salveson, the shipping firm, and Peter's radio shack was in what had been the board room. His microphone dangled from a cathedral ceiling far above, and he drove his wheelchair under it, the rigs being positioned for him to operate them with his toes with the mike over his mouth.

David

[Aub]

What a great story.

Aub

[murphyv310]

Hi.
Well I opened up the crystal a few days ago. I was able to graft the element onto another holder, tricky but I did it. The element was carefully washed with 99% IPA before reassembly and given time for the IPA to evaporate. Result...... No go.
The problem is we don't even know what overtone this crystal is?
Castle Electronics have no parts for FT-480R's and Yaesu have not replied.

[Terry_VK5TM]

There is a group on groups.io - The Electric Handbag - that is dedicated to the likes of these rigs where you might get the info (I've literally just joined today).

https://groups.io/g/TheElectricHandbag

[SiriusHardware]

Can you put the repaired crystal into a basic crystal oscillator circuit to see if the crystal does / does not work independently of the radio?

If you can gather enough technical information there are still some bespoke crystal manufacturers who will make them to order - for example Quartslab (spelling is correct), who can also analyse the characteristics of an existing example and make you a copy of it. In other words, if you were prepared to risk loaning them the crystal from the working set, they would be able to clone it for you.

[murphyv310]

Hi.
Quartzlab have closed down and I belive Mcknights are gone too.
Quartzlab work is done in the Netherlands, I've been informed that prices are high which rather defeats the purpose of a cheap rig unfortunately.
I will test the crystal in another circuit though.

[Richard675]

Sometimes crystals can be “kickstarted” back to life by heating them up. I have done this with a crystal mixing board (80m) in a FT101Z. Just heat up the crystal pin/wire with a soldering iron for a few seconds and then try. You can do this in circuit if you’re careful
(I’m sure I got this tip from a G3LLL article somewhere)

[G6Tanuki]

"Sleeping sickness" was sometimes a problem with crystals in infrequently-used two-way radio gear; it'd refuse to oscillate but when you took the xtal out of the radio and shoved it on a test-set that maybe involved a bit more-vigorous feedback it would come back to life so you'd put it back in the radio and send the thing back marked 'no fault found'.

If the radio then sat unused for a year or two [until the next fireman's strike....] when they needed it it wouldn't work.... and you got the blame.

Rumour has it that flux-contamination from when the can was soldered over the crystal was the cause; I got to just replacing the crystal because it was cheaper than the contract penalty-clause for failure.

[Jon_G4MDC]

This 63MHz crystal is not in an easy circuit. It has various diode switches to make it a stepped VXO. Get the wrong spec and I suspect it won't work as planned.

Icom seemed to be the masters of "rubbering" crystals. They started it in the IC2E. In this set Yaesu has taken the art to new levels.

The 63MHz could be 3rd overtone, so long as they could make 21MHz as a fundamental. By the 1980s that was probably do-able.

In earlier days it would have been a 5th overtone and something more like 12.7 MHz as fundamental. Pye PF1 of 1965 was 5th overtone to hit 85MHz. It's equivalent to a 17MHz fundamental which was the state of the art in the day.

[SiriusHardware]

Sorry to hear of the demise of Quartslab, they were very helpful to me a few years ago and provided exactly the service I mentioned, they analysed an unusual 'band crystal' from an old VXO tuned radio and made me a crystal for an adjacent frequency block by analysing an original loaned to them.

If they've gone I don't know who would be able to provide a similar service now.

[Radio Wrangler]

Originally Posted by Jon_G4MDC

This 63MHz crystal is not in an easy circuit. It has various diode switches to make it a stepped VXO. Get the wrong spec and I suspect it won't work as planned.

Icom seemed to be the masters of "rubbering" crystals. They started it in the IC2E. In this set Yaesu has taken the art to new levels.

The 63MHz could be 3rd overtone, so long as they could make 21MHz as a fundamental. By the 1980s that was probably do-able.

In earlier days it would have been a 5th overtone and something more like 12.7 MHz as fundamental. Pye PF1 of 1965 was 5th overtone to hit 85MHz. It's equivalent to a 17MHz fundamental which was the state of the art in the day.

Definitely third

The pullability of acrystal, in ppm, is inversely proportional to the square of the overtone number.

So, if you want to make 30MHz with a 15 MHz fundamental and a doubler, you get a certain amount of pulling range.

Make it with a 10MHz fundamental crystal and a tripler and you get roughly the same pulling range at 30MHz.

Make it with a 5MHz fundamental, and then double and triple it, you get 30MHz and about the same pulling range. There'll be small differences, but that's it. If the swings don't get you, the roundabouts will.

Now, make it with a 30MHz third overtone crystal and your pullability falls to around a ninth of what you had before. The third overtone crystal will have a fundamental mode, and it will be very close (but not dead on) 10MHz. But notice how it hasn't got the pullability of the plain 10MHz crustal, oscillating on 10MHz and then frequency tripled. Odd?

Make it with a 30MHz 5th overtone crystal, and your pullability at 30 MHz is about 1/25th of what you started out with.

Pulling range in a quartz crystal is a difficult commodity. I needed a VCXO at 100MHz with plenty of range just to get it pullable from wherever it landed to a precise 100MHz. In the end, Vectron made some units for us, using 100MHz fundamental crystals (yes, really!) The cost was rather speial as well. These used 'inverted-mesa' crystals if you want to look up the technology.

The firm who used to make special crystals for me are long gone, I'm afraid.

You could try talking to P R Golledge. They may be able to give you a steer.

Beyond that, there may be a cottage industry firm, probably in China.

David

[murphyv310]

Hi.
I'm wondering about the possibility of removing the original PLL board and going down the route of a more up to date way. I'm not really into modern chips etc but would say a frequency synthesizer way work? We only need to generate frequencies between 133.190mhz & 135.189nhz to cover the full UK 2 meter amateur band. Sorry if this is a daft question.

[SiriusHardware]

The DDS (Direct digital) synthesisers sometimes suggested for this have a reputation for having rather noisy output, unfortunately.

[Terry_VK5TM]

Plus you are going to need a bit of software trickery to account for the stepping of the 63MHz xtal unless you are going to replace the whole chain. I haven't looked in depth at the schematic to see what would be involved.

Re noise etc from the various options, there's not going to be much noticeable difference between AD9851, Si5351, Si570 (the most commonly used ones) although the last one is supposed to be the better of that lot.

Note in the case of the first one, I mentioned AD9851, as driving an AD9850 to 63MHz is asking for a noisy output.

[G0HZU_JMR]

It does look to be optimised for a third overtone crystal and I think it may be possible to tweak the design to work with a tired crystal if you want to try a few things? I can describe how the overtone oscillator circuit has been designed and what the design goals and compromises were if that helps with an initial understanding of the circuit?

Failing this it may also be possible to crudely reverse engineer the crystal parameters if the tuning step sizes are known for each diode switch setting.

[G0HZU_JMR]

If this was my radio and the crystal can't be encouraged to work again then I would try and fix this in slow time. Keep a watch on ebay for a spare FT480R PLL board for example. Even if it takes a year or two to find a spare crystal does it really matter?

I guess the next best option would be to replace the 63MHz oscillator with a stepped synthesiser chip controlled by a PIC/AVR MCU. I just don't think it's worth it unless you are particularly fond of operating this radio.

[ex seismic]

There is a chap called Joachim or something along those lines, in the UK I think, who does crystals to order at reasonable prices. I do not think he has a web site but others on this forum will know of him and how to contact him.

Gordon
G7KNS

[murphyv310]

Thanks Gordon.
Will see if anyone responds with details.