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  1. AndyK11

    Mystery SL-X bias issue?

    Bingo! I got fast blow fuses instead of the slow-blow/timed! New heater fuse probably blew as soon as I turned the amp on! D'oh! Hopefully the right fuses will cure my problem. Times like these I so miss Radio Shack!
  2. AndyK11

    Mystery SL-X bias issue?

    Pins 2 and 7 lead right to the power transformer. 😳
  3. AndyK11

    Mystery SL-X bias issue?

    What do I check next or do to fix it?
  4. AndyK11

    Mystery SL-X bias issue?

    So I am getting 1 VAC in that one socket, 7 VAC in the one that works.
  5. AndyK11

    Mystery SL-X bias issue?

    Changed R28 and R29 to the stock values. Got sound out of the EL34's, but then the volume went down and up. I decided to hard wire the BR3, thinking the burned traces weren't making good contact. I fired up the amp, and blew Fuse # 5. Turns out I hard wired two wires too close, and it must have...
  6. AndyK11

    DSL… the WORST of ALL Marshalls?!?!

    Amazingly, most early JCM2000 DSL's are over 20 years old - and still going! Wonder if the new, wave soldered Vietnam made versions will be working in 20 years?
  7. AndyK11

    Mystery SL-X bias issue?

    R28 is a 68k resistor, and R29 is 27k? R28 should be 22k according to the schematic, and R29 should be 8.2k. Not sure what is going on, or why these should be so wrong?
  8. AndyK11

    Mystery SL-X bias issue?

    I replaced the bias trimmer pot. The new one is nice and clean. But it did nothing to fix the problem. Anyone know what would cause the voltage range at Pin 5 to be very limited when turning the bias pot? There is supposed to be -35 to -50 volts for EL34's, but I am only seeing -39 to -42 volts.
  9. AndyK11

    NVMD - ‘72 1987 (Clip added!)

    The beauty is most issues are pretty repairable on these old classics! Unless your transformer(s) go, most everything else is fixable. Feel better soon!
  10. AndyK11

    New SV20H Day!

    Wonder how hard/easy it would be to wire in a PPIMV, to tame the volume for home use? Even 5 watts is LOUD when you have no master volume!
  11. AndyK11

    Mystery SL-X bias issue?

    Also, with the tubes in, I get a super low volume tone that doesn’t get louder with the master on 4. Normally that would peel paint.
  12. AndyK11

    Mystery SL-X bias issue?

    Fuses are fine, all check out for continuity. I ordered a replacement bias trimmer to see if that helps!
  13. AndyK11

    Mystery SL-X bias issue?

    No, these are just plug and play. They plug into the socket, and have internal wiring that converts to the small tube. I think if the socket was bad, it wouldn’t convert to the new tube correctly - so it wouldn’t work. Not 100% sure though.
  14. AndyK11

    Mystery SL-X bias issue?

    The TAC adapters run 6AK6 tubes at 2 watts, for a total of about 4 watts of Class A with self biasing. If the tube sockets were dirty they wouldn’t work either.
  15. AndyK11

    Mystery SL-X bias issue?

    A bad bias trimmer pot could be part of the problem. If the traces are worn, that would maybe mean bias issues. But, like Peter said, if there’s just low bias, the amp could still sound fine - maybe not great, but not “barely audible”. I haven’t measured the transformers since it is loud and...
  16. AndyK11

    Mystery SL-X bias issue?

    Hmm. Right, the output tubes fuse. It's fine.
  17. AndyK11

    Mystery SL-X bias issue?

    I only see 2 fuses on the board, labeled F5 and F6.
  18. AndyK11

    Mystery SL-X bias issue?

  19. AndyK11

    Mystery SL-X bias issue?

    When I connect to pin 5, and turn the bias control, it goes from 39 to 43 or so. The 2 fuses on the board look fine to me. If they were blown, or the op amp was failing, wouldn’t that kill the sound, even with the Smicz adapters installed?
  20. AndyK11

    Mystery SL-X bias issue?

    I changed the bias caps for good measure. Still doing the same low bias, no sound. Not sure what to check next?

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