Recent content by JJman

  1. JJman

    Master volume in JTM45.... Can it be defeated at will via push pull pot?

    Hey, this Fonzarelli MV loads the PI outputs down as you turn the MV down. I don't think the Fonz would find this to be cool.
  2. JJman

    Power output question...

    1/2 of the human-perceived volume of 150 watts is 15 watts. That's why volume knobs are log taper.
  3. JJman

    SF Champ upgrade project: Questions, thoughts..?

    My 74 (Vibro) Champ was idling at 20watts on the 6v6 when I got it. Use an excellent 6v6 after changing the cathode cap. I guess a 6L6 would not need to be as excellent to take the voltage and/or current these amps run the output at.
  4. JJman

    Does biasing hotter give you more rms wattage?

    In the OP's example, hotter bias (compared to anything close to "normal") will result in less output power. This is from the "earlier" clipping which is often a goal. The reduction in power is minimal especially in the audible world.
  5. JJman

    For cathode biased amp, which way is more accurate to measure plate current?

    OT shunt method is not accurate depending on the internal resistance your meter adds in ma mode. This can be significant in this application, even in an excellent meter.
  6. JJman

    H303a Harmony

    Old wax caps like that are often leaking DC. Interesting how they added a power tranny but kept the higher filament-voltage tubes by ground-tapping the secondary. Much safer yet still lower cost with only one secondary.
  7. JJman

    Moding silvertone amp, locating cathode

    Keep in mind that the bright-cap/switch on a volume pot does nothing when the pot is cranked. And very little when almost cranked.
  8. JJman

    Retensioning tube sockets, when is it necessary?

    You could try testing with some "socket savers" for continuity. However, if the male pins on the SS are larger than "normal" it won't be a valid test and could make the sockets even looser. Or just leave them in and you shall be saved! Gently tilting the tubes around a little, with the amp...
  9. JJman

    anyone know if this tube tester will do a good job testing tubes?

    Very similar to my 920 model. I see an issue. I don't see a 9pin socket (e.g. for 12ax7 type tubes or el84 or many others.) My 9pin socket was changed when I got it and I changed it again myself due to poor contacts. Mine is from 1947 IIRC. It did not have EL84 or 6V6 on its roller but I...
  10. JJman

    Help!!! My new Bassbreaker 15 (with the fix) is unplayable...

    I jammed with a guy who brought his brand new Bassbreaker. Mediocre tone to me but maybe they sound great.
  11. JJman

    Problem with tremolo..

    As mentioned, we don't know if you changed only the PI or also the trem to the EC scheme. The 5E9-A trem modulates the cathode of the PI so changing (only) the PI to cathodine is likely not kosher. You would now be modulating the thing that modulates only one of the output tubes.
  12. JJman

    Looking Into Local Stash Of Nos/anos Vintage El34's - Help With Matching Pairs

    Set the bias to something a little cold on an existing pair you already have. Change one tube on one side and measure the milli-voltage on that side via the probe port. Assign that number to that tube and take it out. Put in another and measure and assign that # to that tube. Keep changing...
  13. JJman

    Open secondary on reverb transformer

    I would be concerned with WHY the secondary opened. The standard suspect would be that it was driving a shorted load.
  14. JJman

    More fun with Deluxe Reverb project (PT replacement, plus blackface)

    My '71 distorted above 3 until I changed out the original speaker. Have you tried a different speaker/cab?
  15. JJman

    2204 with PPIMV to make it more basement friendly?

    The problem you are referring to is with the taper of the pot. Get a new pot with a more logarithmic taper. Maybe the stock ones are linear? Larmar is cool and I like mine on homebrews and my '71SFDR but that's really a separate topic from correcting a taper issue.
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