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  1. G

    JVM410H Issue

    OK, So I was correct, only one EL34 was working. Put in some near new EL34's and biased it to 70mv per side and what do you know. It has roared back to life. Just need to replace the preamp tubes as they are also 14 years old. So a good result. Cheers
  2. G

    JVM410H Issue

    I also forgot to mention. I placed the bias probes on all 4 sockets, as I have the one x 2. So I tried every EL34 and only one give a current the #1 EL34. So I swapped #1 with # 4 - EL34. and I now have the 38Mv on the opposite side.Confirming it's the tubes. Which I think proves that 3 x EL34's...
  3. G

    JVM410H Issue

    What if I remove the working valve and place in the opposite socket V1 to V4. if that then shows a reading, then all 3 EL34's are dead. If that doesn't change and I still get zero, then it's something else. let me know, Cheers.
  4. G

    JVM410H Issue

    see image attached.
  5. G

    JVM410H Issue

    I should have mentioned all power tubes are glowing
  6. G

    JVM410H Issue

    Hello Southpark, So remove all the power tubes and I'm not sure how to check the bias voltage. They are 14 years old. Cheers.
  7. G

    JVM410H Issue

    Just had another look. I don't have the original schematic for the JVM410H. But FS3 and FS4 don't have fuses but now have wire in it's place. Does that sound right?
  8. G

    JVM410H Issue

    Hey Thanks, I just had a quick look inside. Looks very clean and original. I can't see any burntout resistors or capacitors. I also checked my multimeter on the 3 pin connector, just to be sure. 0Mv on one side and 35Mv on the other. Can an amp run safely on 1 power tube? I am hoping to replace...
  9. G

    JVM410H Issue

    Hey Guys, So I have a JVM410H that was loaned to me by my band member. I took it home and tried it out, WTF?? I have owned 2 JVM410H and 1 JVM410HJS before. It just sound weak and dull and lacked gain. So I checked the tubes. Amp manufactured date - M2007 - 34 -1150. EL34's are also WK32/07. So...

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