Kenwood TS 830S

Discussion in 'Electronics Repair' started by Nemo1956, Jun 27, 2017.

  1. Nemo1956

    Nemo1956

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    Im not having a good month.
    Now my much beloved TS830S has gone tits up on my.
    It started to fail two weeks ago when i switched it on no RF output. So I left it running for about 1 hr and then 60 watts. OK that will do. But this weekend nothing at all. so I took some measurements only to find that the 12AY7 valve base had problems. So I pulled the RF board out and I found cracks around the solder joints. The pins where in a mess so I had to remove the base and clean up all the pins. Put it back and re-soldered it in. But as the board was out I took some other measurements and found the 12AY7 grid leak resistor was open circuit and the one of the two cathode resistors had gone a bit high. Both replaced. So i put it all back together. Switched it on and still on RF output but then I could see the HT volts dropping to 350 volt and not 850 volts.
    I think I may have a short in one of the PA valve now ?
    Has any one had anything like this???

    Oh well it is over 25 years old so I guess it would like a bit of attention and TLC.
     
    Last edited by a moderator: Jul 14, 2017
    Nemo1956, Jun 27, 2017
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  2. Nemo1956

    davenn Moderator

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    any mode ? AM, SSB, CW ?

    start with seeing what is coming out of the pre-driver and driver stages
    From memory, they had a pair 6146B's as the finals

    I assume you have a service manual ?, they are readily available online

    your one is only 25 yr old ? ..... gosh those things go back 40+ yrs
     
    davenn, Jun 27, 2017
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  3. Nemo1956

    Nemo1956

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    Hi there. Yes it has 6146's in the final and a 12?? in the driver stage. I replaced the valves with a second set but still nothing. Guess I need to strip it.
     
    Nemo1956, Jun 27, 2017
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  4. Nemo1956

    davenn Moderator

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    I haven't looked at the diagram .... maybe a 12AX7 .... think they were often used as low power transmitting tubes
    been years since I was regularly playing with tube tech

    also make sure ALL switches ... band switching etc are all clean, crappy worn contacts can do all sorts of weird things
     
    davenn, Jun 27, 2017
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  5. Nemo1956

    Nemo1956

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    I have looked at all the switches and all seem to be in good order and clean. Yes the 12AX7 Could not remember it. Like you its been some time since I have worked on vintage equipment. But Im vintage as well. LOL I think the problem is the driver section as I also don't see any drive level. I need to take it to bits and have a good look at it. I love my 830 it's one of the better radios of it's day.
     
    Nemo1956, Jun 27, 2017
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  6. Nemo1956

    Nemo1956

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    Im not having a good month.
    Now my much beloved TS830S has gone tits up on my.
    It started to fail two weeks ago when i switched it on no RF output. So I left it running for about 1 hr and then 60 watts. OK that will do. But this weekend nothing at all. so I took some measurements only to find that the 12AY7 valve base had problems. So I pulled the RF board out and I found cracks around the solder joints. The pins where in a mess so I had to remove the base and clean up all the pins. Put it back and re-soldered it in. But as the board was out I took some other measurements and found the 12AY7 grid leak resistor was open circuit and the one of the two cathode resistors had gone a bit high. Both replaced. So i put it all back together. Switched it on and still on RF output but then I could see the HT volts dropping to 350 volt and not 850 volts.
    I think I may have a short in one of the PA valve now ?
    Has any one had anything like this???
     
    Nemo1956, Jul 11, 2017
    #6
  7. Nemo1956

    dorke

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    Swatde kharp.

    I haven't ever used this SSB/CW HAM radio.

    Something seems to be wrong with your description:
    Where did you get the idea that HT of the 12AY7 (dual Triode audio)should be 850Volts?
    350V sounds o.k(even a bit high).

    Did you check the output in CW mode?
    What are you using to check the output power?
    Is the receiver part working?

    Do you have a schematic diagram or service manual of the unit?

    Do you have a scope?
     
    dorke, Jul 14, 2017
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  8. Nemo1956

    davenn Moderator

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    I have moved more info from another thread to this one .... @dorke have a reread from the new start of the thread and it may now make a bit more sense to you
    and some of your Q's will be answered .... like yes we got a manual :)

    Paul and I had started talking about this problem some days ago .... I think he typo'ed in his post above and forgot the other thread and that I said that it was a 12AX7
    (not a 12AY7)
    The 12AX7 was a common transmitter driver tube for a single or pair of 6146B finals

    service manual link on my home page site

    http://www.sydneystormcity.com/TS830S_Service_Manual.pdf
     
    Last edited: Jul 14, 2017
    davenn, Jul 14, 2017
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  9. Nemo1956

    dorke

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    Thanks Dave,
    From the SM :
    V1,the driver Pentode is 12BY7A .

    So still, HT of 350V looks o.k.(a bit high).
    Please check all DC voltages on V1 with a DVM ,including the heater(ACV!)
    per the SM :

    V1.jpg V1.jpg
     
    dorke, Jul 15, 2017
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  10. Nemo1956

    Nemo1956

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    Hi all Many thanks to you all for your kind replays.
    Over the weekend I had a very deep look at this. My first thoughts where that I miss aligned the switch in the PA stage but no it's ok but the coupler will need to be replaces soon as it has cracked. I measured all around the Driver valve (12BY7) and it looked ok so I moved on to the PA section. There I found that they was no cathode volt and the anode volts are 300 +/- volts short when in transmit. This I traced to the power supply board and found no end of problems here. Resistors open circuit and high in value the doubler stage the capacitor was open circuit and many others like it or leaking. I just don't know how this radio worked at all in this state.
    Anyway I need to order some new capacitors now as I have replaced all the resistors now.
    I Let you all know how i Get on when I get the new parts.
    Thanks again for all your help.
    Paul
     
    Nemo1956, Jul 17, 2017
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  11. Nemo1956

    Nemo1956

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    Up date for you all.
    Sadly after doing all this work on my 830. I have discovered that the mains transformer is the main source of the problems. Its got a shorted turn on the HV winding. And now gets very hot after only running for 30 seconds. Very sad so that makes my much loved TS830 scrap. I had through of rewinding it but its the second winding after the primary winding so I would have to completely dismantle the thing to do it. Then get it rewound. So I have decided that enough it can't do any more for it.
     
    Nemo1956, Jul 19, 2017
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  12. Nemo1956

    davenn Moderator

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    far out, that's a total bummer :(

    maybe you could look around for some one that is selling one for parts and rat out the tramsformer
     
    davenn, Jul 19, 2017
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  13. Nemo1956

    duke37

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    How did you determine that the shorted turn is on the HV winding? Shorting to an adjacent turn will make very little difference to the winding resistance and all windings are inductively coupled so it is difficult to find the origin.
     
    duke37, Jul 19, 2017
    #13
  14. Nemo1956

    Nemo1956

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    I measured it to one of the other winding it should be open circuit but it it reading around 30 ohms and the transformer is getting very hot indeed after a very short time.
     
    Nemo1956, Jul 19, 2017
    #14
  15. Nemo1956

    Nemo1956

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    Yes I have had a look for one on ebay but nothing there at all. but some other boards for sale but no transformer. Maybe it a common fault on these old radios after it's been running for some years continuously like i think this one has.
     
    Nemo1956, Jul 19, 2017
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  16. Nemo1956

    Nemo1956

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    Hi all. Update for you all. I removed the damaged transformer and had a good look at it but can't see anything that shows me where the problem is.

    As i live in Thailand there are many places that will rewind a motor for you so I just took it up to the closest one and said can you find the fault on here. I told him I think it has a shorted turn between two windings. At first he just said no can not do but after having a longer chat with him. He said if I remove the bobbin he would look at it.

    This I did. (not an easy task) Them took it back. He looked at and said come back in two days.

    Well that was last week but I have not had time to go and see what he has done with it.
     
    Nemo1956, Jul 27, 2017
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