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Old 14th Jun 2021, 10:09 pm   #1
Janner7859
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Default Trio (Kenwood) TS-780 2m 70cm Ham Radio.

Hi

My name is John, and I am restoring an old Trio (Kenwood) TS-780 2m 70cm Ham Radio. A previous owner has butchered it a bit, with a soldering iron, by the looks of things. I have managed to get the digital display working and it does now receive signals, although it is not very sensitive. I need to replace the RF board, so if anyone has any idea where I might get hold of one, I would be really grateful.

Thanks

John
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Old 15th Jun 2021, 1:43 am   #2
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Default Re: Trio (Kenwood) TS-780 2m 70cm Ham Radio.

Hello and welcome!

I've no specific experience of that set, just the much earlier TS700.
Was there a Mutek front end for that model?

Is it equally insensitive across the band and on all modes? What does the S meter show? Do you have a signal generator and other test gear?

David
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Old 15th Jun 2021, 7:46 am   #3
SiriusHardware
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Default Re: Trio (Kenwood) TS-780 2m 70cm Ham Radio.

I'm away from base but I think I have an almost working 780 in the loft - if I remember correctly there was a problem with UHF RX because the previous owner's spouse had accidentally spilt coffee on the top but hopefully you would be able to make one good one from two. I've kept it for years hoping a parts donor would turn up but you are welcome to it if it will get your radio working.

I know you are a long way from me but it so happens that I will be in Devon in July, so let me confirm (when I get back) if the radio is what I think it is and then I will get back to you via PM.

Of course if you can fix the radio with the help of others here before then, all the better.
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Old 15th Jun 2021, 9:07 am   #4
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Default Re: Trio (Kenwood) TS-780 2m 70cm Ham Radio.

Quote:
Originally Posted by Radio Wrangler View Post
Hello and welcome!

I've no specific experience of that set, just the much earlier TS700.
Was there a Mutek front end for that model?

Is it equally insensitive across the band and on all modes? What does the S meter show? Do you have a signal generator and other test gear?

David
Hi David, thanks for the reply.
I'm not entirely sure what you mean by a Mutek front end. I know they did pre-amp modules for radios, so if that's what you mean, then no it doesn't have one.
It is definately the RF board that's causing the weak signal, I can get it to work intermittently, but this thing has really been messed about with. The S meter will barely move, even on strong local signals. As for the signal generator, no I don't have one. The only test gear I have is an oscilloscope, a multimeter, and a logic probe. I am a semi retired PC engineer with a keen interest in electronics and radio.

John
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Old 15th Jun 2021, 9:15 am   #5
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Default Re: Trio (Kenwood) TS-780 2m 70cm Ham Radio.

Quote:
Originally Posted by SiriusHardware View Post
I'm away from base but I think I have an almost working 780 in the loft - if I remember correctly there was a problem with UHF RX because the previous owner's spouse had accidentally spilt coffee on the top but hopefully you would be able to make one good one from two. I've kept it for years hoping a parts donor would turn up but you are welcome to it if it will get your radio working.

I know you are a long way from me but it so happens that I will be in Devon in July, so let me confirm (when I get back) if the radio is what I think it is and then I will get back to you via PM.

Of course if you can fix the radio with the help of others here before then, all the better.
Hi, and thanks for the reply.

That would be great if you do have one, because to be honest, there are one or two other things that could do with replacing. If those parts are in better condition than the original ones, then I could swap them out too.

Look forward to hearing from you.

John
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Old 15th Jun 2021, 10:20 am   #6
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Default Re: Trio (Kenwood) TS-780 2m 70cm Ham Radio.

This looks like it may be heading towards the best possible outcome!

Mutek was a firm headed by Chris Bartram, an excellent RF designer (who also plays a mean fiddle sometimes at Microwave Roundtable meetings) He made little add-in preamp boards for a number of sets like the FT290, but he also made complete replacement front-end boards for a number of the larger size VHF/UHF radios. He was able to develop something which both gave a lower noise figure and a higher overload margin than the originals. This is an indication that the designers back in Japan either weren't quite on the ball as far as optimum design was concerned, or a useful amount of performance was being wasted to save a quid or two on parts. I'd put my money on a bit of both.

David GM4ZNX
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Old 15th Jun 2021, 3:27 pm   #7
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Default Re: Trio (Kenwood) TS-780 2m 70cm Ham Radio.

I put the radio I'm thinking of away in the loft probably 15-20 years ago and I THINK it is a 780 but let's not be too hasty. I'm not back at base until next week so that's the earliest I can take a look.

I remember that at the time it was put away it was working fine on 2m TX and RX and on 70cms TX.
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Old 15th Jun 2021, 5:13 pm   #8
Janner7859
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Default Re: Trio (Kenwood) TS-780 2m 70cm Ham Radio.

No problem, I am hopeful that the radio you have is a 780, but if it's not thank you anyway for taking a look when you get back. It's not urgent, it's just a project that I am working on as a hobby.

Thanks again.

John
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Old 21st Jun 2021, 6:18 pm   #9
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Default Re: Trio (Kenwood) TS-780 2m 70cm Ham Radio.

An update on this. My loft hulk is a Trio branded TS780 and it's working quite nicely on 2m just now. The main tuning control feels lovely, display bright and clean and clear. Some of the pots (especially squelch) could do with a squirt of Servisol.

I'm glad this thread prompted me to look at it because the 3 x backup batteries (Alkaline) had gone into terminal decline and have damaged the battery box, but luckily nothing else, and the backup battery box is just one of those removable plastic trays with PP3 style studs on the end, easily replaced.

I've just sent an email off to the previous owner, who gave it to me initially to fix if I ever had time, but then his interest in AR waned soon afterwards and I never did have the incentive to fix it - as explained earlier there was a suggestion of UHF RX not working due to a small amount of liquid spillage into the top of the unit. Many years ago someone here did post to the effect that they were breaking up a 780 but by the time I found the post the boards from that radio had sadly already been stripped of parts. An opportunity missed.

I'm just making absolutely sure the original owner of this radio has relinquished all interest in it, then I will proceed from there.
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Old 21st Jun 2021, 7:11 pm   #10
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Default Re: Trio (Kenwood) TS-780 2m 70cm Ham Radio.

OK, thanks for the update.

John
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Old 30th Jun 2021, 5:52 pm   #11
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Default Re: Trio (Kenwood) TS-780 2m 70cm Ham Radio.

A more subdued update on this: After a lengthy wait for a response from the owner of the set I have had here in my loft for quite some time, he now tells me that while he's not active on AR any more himself a friend of his has just revived his lapsed licence and would like the set.

I can only apologise to John for the premature offer of the set - the owner has shown no interest in it for at least a decade and I thought with my heading down to John's neck of the woods shortly the opportunity to pass it on would be too good to miss.

I've suggested John starts a repair thread for his radio in 'Vintage Amateur and Military Radio'.
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