Kenwood TS-2000 problem

Discussion in 'Radio Circuits, Repair & Performance' started by KC4UMO, Apr 26, 2015.

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  1. KC4UMO

    KC4UMO Ham Member QRZ Page

    That would suck. but knowing the guy that had it dont think that was the problem...
    Have not gone far enough to see if it transmits. It draws so much current when connecting the power wires it worries me.
     
    Last edited: Apr 27, 2015
  2. KC4UMO

    KC4UMO Ham Member QRZ Page

    Came home right after work.
    Unsoldered the bases of both C5125 transistors.
    No more current draw with radio off. When turned on I am getting around 2 amp current draw on the power supply meter which I don't trust because they are not that accurate.
    Next step is to remove both C5125 transistors and check for a short.
     
  3. KV6O

    KV6O Ham Member QRZ Page

    Cool - looks like you found the problem! I had a short in one of the drivers (1972's, IIRC) on my TS-2000 about 10 years ago, radio was drawing about 8-10A on receive, would get very warm and the fan would run constantly. Put in a new matched pair, been fine since.

    Steve
    KV6O
     
  4. KA5IPF

    KA5IPF Ham Member QRZ Page

    Ok I'm lost now. I had the understanding it was blowing the fuses when the radio was powered up. The last notes make it seem it's blowing fuses when the power supply is turned on. Which is it? It will determine the next step.
     
  5. KA5IPF

    KA5IPF Ham Member QRZ Page

    Now you're getting somewhere. Probably one is leaky and turning on the other, see the previous note about the drivers. They will probably ohm out. Be sitting down when you price them.
     
  6. KC4UMO

    KC4UMO Ham Member QRZ Page

    Sorry to confuse you Clif. But you are right on both. When I first tested the rig it would blow when powered up. Back on post 17 is where I noticed the current when connecting the supply with radio off. I did not check the current draw with radio off the first time. So did not really notice it until post 17.
    Tell me, is it possible the transistor(s) got worse after the first power on and started drawing more current?


    Oh boy. Now I am afraid to look lol.
    I do have a set in stock I bought a while back.

    But at the moment I am have a good time just sitting here using it as a receiver.
     
  7. G4COE

    G4COE Ham Member QRZ Page

    Had that very thing with a Icom... one of the push-pull drivers was s/c between collector base, this was turning the PA bias regulator 'TX ON line' hard on causing lots of current through the finals even in the RX mode..... this is easily overlooked, " it's the finals the guy said".

    The bias for driver and the finals bias are 'switched', the bias ON line was receiving the voltage from the leaky driver.

    Dave
     
  8. KA5IPF

    KA5IPF Ham Member QRZ Page

    I don't know about Icoms but Kenwood has a separate bias circuit for the drivers and finals, they can't crossfeed. On the newer TS2000's using fets there are several bias circuits, one for each final transistor (4 total, 5 if you count the 450 circuit), one for the driver and one for the predriver.

    If you have a pair put them in. Make sure you understand how the bias adjust circuit works and is adjusted. Much confusion there.
     
  9. KA5IPF

    KA5IPF Ham Member QRZ Page

    Easy to check, the bases are lifted so check the voltage on each base. One will show 13.8v. Check the pads for the bases also, just in case. All the pads and bases should be at zero.
     
  10. G4COE

    G4COE Ham Member QRZ Page

    @ KA5IPF

    I don't want to take this thread off-topic nor hijack it. Have you ever used Eleflow replacement drivers for the TS2000 (2sc1971 & 2SDC1972)? The ones I ordered wouldn't fit in, they're 1mm or so too wide, now I used them in the past in they 'dropped right in', but these I think may be dodgy I dunno

    1) The print is easily smudged
    2) The tabs and pins look far too shiny for my liking, nothing like the last ones I fitted

    I got them from a recommended site from Eleflow USA... there's a lot more to this specific story I don't mind going into but I don't wanna change the op topic.

    Be warned:
    Should anyone order ANY RF power transistors be very careful of the source there are plenty of forged ones around.... sadly this is becoming same with audio power transistors, there are bags of info on the internet.

    In my Icom case, the driver and final bias was separate, it was turning the 'bias ON line' hard on, it was easy to find as been mentioned, by either lifting the collector of the drivers or the bases of the finals.... far far better than go pulling the transistors out.

    Dave
     

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