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Old 26th Mar 2023, 10:12 pm   #1
John M1JWR
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Default Kenwood TS50 faulty.

Hope everybody is well
been given a ts50 to look at, i realise this will be far more complecated than the ptbm 121 and 125 boarded radios i had become fermilliar with, the owner said that it put out magic smoke on tx one time and he switched it off, and hasent been near it since, that was a couple of years ago, i know this model is prone to smd caps going fubar, upon visual inspection the ones i have seen are ok so far, including the one on the back of the display, so far the only checks i have done is to power it up which it does and check for rx, which it also does with no issue, dared tx on 10w low power at which point it goes off and boots stright back up again with no smoke, i did that with the variable bench psu which is only 3 amp max diddent take notice if it maxed out or not which is possible, just needing to know if it would be ok to try that with the bigger psu or not or to go in and check over output transistors etc first, the radio does use about 900mw on rx, the order of the day is if its going to cost too much to get going then he is either going to sell it spares or repair or have a rx only radio, he does also have the dedicated atu for this radio. i know the finals if it came to that are not cheap, i have just done a basic test so far to see what it does and dosent do before i went in deeper, regards to all
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Old 28th Mar 2023, 9:45 pm   #2
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Default Re: Kenwood ts50 faulty

Hi John. I have a working TS50. Have you managed to lay hands on the circuit diagram?

My feeling is that even on the lowest FM TX power (10W out), a 3A power supply just isn't going to cut it bearing in mind that those 3A PSUs were typically sold for powering 4W CB radios. If starved of power due to insufficient maximum current available the symptom you have described would be exactly what I would expect, the radio would crash and restart when you try to do something high-demand (like transmit).

The much heavier (25A) PSU that I run my TS50 on has a current meter on it, I'm busy tonight but if I get a chance tomorrow I will see what it draws at 10W FM into a dummy load.

Where there was smoke, there should be smell, so if you lift the covers and follow your nose you may get close enough to find something which actually looks burned, or you may see smoke streaks pointing to something which has burned up.

These were very popular radios and were produced for a long time but I think they have been out of production for a while and spares, especially RF output devices, may prove to be unobtainium now.

If it got to the point where it was going to be scrapped I might consider offering a meagre amount for it as a 'box of spares' for my still working unit, but if I am honest the owner could probably get more for it than I could offer if it was offered the way you have described it on an auction site.

However, that's all rather premature. Let's see what's in there first.

Last edited by SiriusHardware; 28th Mar 2023 at 9:56 pm.
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Old 28th Mar 2023, 11:50 pm   #3
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Default Re: Kenwood ts50 faulty

hi sirius
theres a story to tell here as i have discovered, i used the bench psu because i knew that it would shut down if something iffy happened or something unexpected, i thought there would be no output going by the owners discription of what has happened and if there was smoke then whats knackered is knackered, but the radio used amps so that was unexpected, so off with the lids, somebody has changed the memory battery and its had a mars mod its had a diode cut and a plastic sheath put over the cut end, all good there, had a look at some of those smd caps that are known to leak out especially the one on the front panel, trx bench has done some major repairs in that area on other radios, this one is lucky no leaks....yet ! at the back end where the antenna goes in there is a board with lots of coils, cant remember what its called, and under that
there is the tx board, thets where the problem should be, so removed the top one and checked the tx board, no black areas no smells nothing, checked the drivers with meter all seem ok, wasent 100% shure about one of the 2sc3133's, but was hopeful enough to put it back together and try on the main psu, palstar ps30m, i think if i used it first there would be no give with that one, turned the ts50 down to 10w setting as i only have a 20w dummy load 27.555 fm keyed the mike and stable 10 output, am about 6w and swings upto around 10w and usb will do the same with more voice, well whats going on here then, rang him up and told him the radio works at least on 10w via my testing anyway, i will think of a way to test with 50w at the weekend, colt black shadow has been on sometimes recently monitoring super bowl so its still going strong
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Old 29th Mar 2023, 1:15 am   #4
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Default Re: Kenwood ts50 faulty

Very strange, a ghost fault. Given the complexity of those things I would be happy that it still seems to work, but burnt things rarely heal themselves so the smoke had to come from something.

If there is still a fault there, no doubt it will make itself known sooner or later.

All this talk of leaking SMD caps has me a little bit worried about mine, I should probably have a scoot around because it would be a pity to lose it. I have both of the ATUs for mine, it came with the longwire one (AT300?) and at the first rally I went to after I had acquired it, I happened to spot the coaxial ATU (AT-50?) very cheap on a bring and buy. Apart from a blown internal fuse there was nothing wrong with it.

I used my TS50 a lot during the early years of my A ticket, at the time I was a field engineer driving around for much of the day and I had a full set of those Valor Pro-Am single band aerials. It is still my only multiband HF radio.

For the past 15-20 years or so it has been my main base HF radio but the racket coming out of all the surrounding routers, computers, switch mode PSUs and powerline network adaptors, most of which are not under my control, have made it impossible to listen to HF here now.
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Old 29th Mar 2023, 10:54 am   #5
John M1JWR
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Default Re: Kenwood TS50 faulty.

maybe get the tuner off him and have a look at that, as this radio would've been sitting on it at the time
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Old 29th Mar 2023, 12:03 pm   #6
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Default Re: Kenwood TS50 faulty.

If you mean the AT-50 coax tuner, it is the same size and shape as the TS-50 and is often (as you say) used like a 'plinth' with the radio standing on top of it, so if any smoke emanated from that then it may have looked as though it was coming from the transceiver.
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Old 29th Mar 2023, 1:03 pm   #7
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Default Re: Kenwood TS50 faulty.

The TS50 was such a popular rig in its day with a long production run, but now getting quite long in the tooth. As a consequence, many are malfunctioning, often due to the small conventionally sized electrolytic capacitors, which - being mounted close to the PCB - look like through-hole components but aren't. They look innocent enough but as well at developing a high ESR, they can leak and corrode the copper tracks underneath the caps, which isn't apparent at first sight.

There are lots of youtube videos by those who repair them professionally, two of whom stand out.

Firstly, 'Radio Repair Shop'. 294 videos of repairs of a wide range on amateur equipment.

Several are relevant to the TS50. The first three might be a good place to start:

'Kenwood TS50 Capacitors and previous repairs gone bad'.

Part 1 Evaluation:

https://www.youtube.com/watch?v=z8Mv...o5Nbu&index=71

Part 2: Kenwood TS-50 Display board trouble shoot and repair:

https://www.youtube.com/watch?v=_uN3...o5Nbu&index=70

Part 3 – troubleshoot and repair transmitter:

https://www.youtube.com/watch?v=czIxQqAqjE0

Kenwood TS50 Display Problem:

https://www.youtube.com/watch?v=W6I8VhM5_j0

Kenwood TS50 Repair:

https://www.youtube.com/watch?v=w1tndknljnA

Secondly, 'TRX Lab' - 265 videos on a wide range of amateur radio repairs:

https://www.youtube.com/@TRXLab/videos

Some of relevance to the TS50:

Several aging issues - ‘KENWOOD TS-50 and AT-50 are getting old and needs love’:

https://www.youtube.com/watch?v=9C2qsosGok4

Kenwood TS50 no function/fixed crazy fault:

https://www.youtube.com/watch?v=Rr-6mOxbewk

Kenwood TS50 needs urgent intensive care in order to survive:

https://www.youtube.com/watch?v=r_TCZ41A51c

Kenwood TS50 intermittent no power and other odd behaviour:

https://www.youtube.com/watch?v=6em059oiLGA&t=1s

ALC Repair:

https://www.youtube.com/watch?v=c7c0iZOQimg

Rather a lot to go at, but you can pick and choose as you wish.

I hope that may be of some help.

Good luck with it.
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Old 29th Mar 2023, 1:17 pm   #8
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Default Re: Kenwood TS50 faulty.

Thanks David, that may save a LOT of time. I've only ever taken mine apart twice, once when I first got it because it was going straight into TX whenever it was put into CW mode - caused by a faulty switch integral to the CW key socket, a replacement for which was still available from Kenwood service and parts agents at the time. I had to take it quite a long way apart to replace that. Quite common, I have heard of other people who 'solve' it by just keeping an unterminated plug in the CW key socket.

The only other time was to replace the memory backup battery - there is an official sequence for how to go about that otherwise the replacement battery runs down quite fast - I can't remember the details but someone may have covered it in one of your linked videos.
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Old 30th Mar 2023, 12:42 am   #9
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Default Re: Kenwood TS50 faulty.

I did watch some of those vids with interest, as i knew nothing about ts50's, was at least handy to find out what goes wrong and where things were, doing smd components is out of my skill set, i did tell the owner to send it to somebody to replace them, i did see one or two elna thru hole caps in there aswell, i know from the hi fi world that they can be troublesome, i did take some out of a denon cd player some time ago and replaced them with panasonics, it did also have some elna cerafine caps in there aswell, they are more reliable and are proper audio caps. when ive finished my tests on the ts50 i will get it back to him and get the atu, that may tell a different story, he also has another radio he hasent used in a while a superstar 3900 that has carrier on ssb tx, carrier balance was checked last time and was ok then he moved it and carrier came back on ssb tx, so in that case mr and mrs dry joints will be the port of call with that one, more pairs on specs then !!
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Old 30th Mar 2023, 12:51 pm   #10
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Default Re: Kenwood TS50 faulty.

Ref: The 3900, don't overlook the possibility that it's just a physically intermittent carrier balance preset, if there is a preset (I'm not so familiar with those ones).

For the removal of surface mount caps you really need TWO soldering irons with fine needlepoint tips. Put a bit of lead-tin solder on the projecting end of each 'foot' of the cap and then heat both sides at once and just use the two irons to 'tweezer' the part off the PCB while the solder is melted on both sides.
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Old 2nd Apr 2023, 3:04 pm   #11
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Default Re: Kenwood TS50 faulty.

yes, i see trx bench used a double headed type iron aswell, i have now checked the radio for 50w output and no smoke, so yes, hmmm, us mechanical types say let it develop !!! i will be seing the owner next week end so its future is of course up to him, ive advised him to get the caps replaced as not a question of if they will go bad but when, will be going up with my iron etc to look for any dry joints in that 3900 to start with, then work on the trimmer itself after that,i did put a dab of switch cleaner on it last time and exersized it, and then look over that atu to see if the "smoke" came from there
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Old 3rd Apr 2023, 8:02 am   #12
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Default Re: Kenwood TS50 faulty.

With the open-frame type of presets usually used in such radios I have sometimes seen cases where the metallic 'wiper' part has been bent slightly upwards away from the track it is supposed to make contact with, so that it works either intermittently or not at all.
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Old 18th Apr 2023, 11:57 pm   #13
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Default Re: Kenwood TS50 faulty.

apologies for not returning sooner, hadent been able to return ts50 to owner until yesterday as his aged mother is very ill, anyway now i have with the info that it is ok at the moment and to have the caps delt with as soon as he can, i do now have the tuner here and hopefully tomorrow i can take pics of the insides as there dosent look anything visably wrong with it so far, i also have his 3900 here, as my very limited level of expertise is limited to certain cybernet boards, i have done some basic checks so far and 1 adjustment, this is as far as i can see a single final output version from 1994 made by crt, somebody has been inside before and turned ssb upto 20w output or a bit more, this is apparently bad for this model as the spec is 12w ssb and 4/5w am/fm, so the adjustment was to put ssb back to around 12w, i noticed am/fm was very low and diddent know until i looked inside for the trimmer that it is connected to s rf pot on the front panel as a variable power out, it is factory and there is a little mark on the front that when lined up is 4w so thats all good, i have reflowed the rv7 joints and one or two others in the area, havent done a readjust on vr7 as yet,noted in your comment, i have also read that vr's in these radios can go duff over time, i can possibly replace it with one out of the scrap 121 chassis as those are the same value as a get by for now
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Old 22nd Apr 2023, 11:33 pm   #14
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Default Re: Kenwood TS50 faulty.

interesting thing with that 3900, got a little time with it today, i de soldered rv6 trimmer out of scrap 121 chassis just incase, i adjusted the 3900's carrier balance with original pot to dead minimum and no solid carrier after that into dummy load, also as a test i put it into a resonably resonant antenna on 27.205 usb it has swr of 1.3 to 1 on there, the solid carrier returned, s3, it does do normal ssb i will call it splatter carrier on top of that, then i put it onto long wire, i have to be quick on tx as swr with this is miles out on 27mhz, and guess what no solid carrier at all, just your normal splatter carrier, just like the dummy load, is this just an anomaly with 3900's or what, because now i dont think its the trimmer, or is this normal for 3900's as ive never owned one or operated on one.
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Old 23rd Apr 2023, 10:00 pm   #15
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Default Re: Kenwood TS50 faulty.

back on topic please find enclosed pics of tuner, one black mark but dont think it was caused by anything electrical, mint inside really
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Old 24th Apr 2023, 12:05 am   #16
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Default Re: Kenwood TS50 faulty.

I wonder if the patch lead between the TS50 and the ATU was the actual failure? Did you get that with the ATU?

Which ATU is this, the AT-300 longwire tuner or the AT-50 coax-fed tuner?
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Old 24th Apr 2023, 12:54 am   #17
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Default Re: Kenwood TS50 faulty.

its the at50 co ax fed one
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Old 24th Apr 2023, 2:37 pm   #18
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Default Re: Kenwood TS50 faulty.

I haven't tried it but I don't imagine the AT50 works too well with a random length of wire connected to the centre terminal of the ANT-OUT socket, that is really what the longwire tuner (AT-300) is for.

For the moment it seems like you are chasing after a ghost - all you can really do now is see if the fault either ever or never re-occurs.
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Old 24th Apr 2023, 9:54 pm   #19
John M1JWR
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Default Re: Kenwood TS50 faulty.

i think you are correct, bit like the ss3900 that seems fussy with antennas,could only go by what my mate said, probably take it all back to him at the weekend and he can soak test it all at his leasure, thanks for your input as always
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