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  1. 89DF8D1B-F124-4825-B8C5-A52DCB3A2D6F

    89DF8D1B-F124-4825-B8C5-A52DCB3A2D6F

    • saranden
    • Media item
    • Comments: 0
    • Category: Marshall Amps
  2. CC4F8824-D4E5-4908-A3F6-58FCFD2E1091

    CC4F8824-D4E5-4908-A3F6-58FCFD2E1091

    R26 damage
    • saranden
    • Media item
    • Comments: 0
    • Category: Marshall Amps
  3. 3146EDEA-7D71-4E37-84C8-C444DA277E37

    3146EDEA-7D71-4E37-84C8-C444DA277E37

    V5 heat damage
    • saranden
    • Media item
    • Comments: 0
    • Category: Marshall Amps
  4. S

    JCM900 4100 high plate voltage! Any help

    It went really well, I took all the advice I was given, decided to change the valve sockets for ceramic ones which made it look a little more sophisticated! However, one fault I could not fix is, when you flick the switch from 100w to 50w on the back of amp switch, the amp will not work apart...
  5. S

    JCM900 4100 high plate voltage! Any help

    Geez ah break Fastdave. I'd loved to have gone to Uni, but circumstances you know. I'm a diy'er with common, and you know, some people have a lot of common but no sense!!! I'm a quick learner especially when it's a subject that you've loved since you were knee high. It never gets boring...
  6. S

    JCM900 4100 high plate voltage! Any help

    I've just received my 4 new EL34 sockets and will install them. It is really of no use asking me anything technical. I have took my guidance from all of the brilliant techs above, including earlier on the "check the socket for arcing". I had the amp running for an hour before doing final...
  7. S

    JCM900 4100 high plate voltage! Any help

    sorry RussBert. with the loose tubes I was getting erratic reading. Now i realize that, i will remedy it. The readings I have listed above, are made after the amp was turned on for about an hour, fully warmed up. I checked and double checked. Hope that makes a bit more sense. I swapped the...
  8. S

    JCM900 4100 high plate voltage! Any help

    try again
  9. S

    JCM900 4100 high plate voltage! Any help

    here the Bias reading view. Im going to order 4 new octal sockets. do you think ceramic is better? sorry the picture is up-side-down!!!!! 36.6mV
  10. S

    JCM900 4100 high plate voltage! Any help

    OK. Here's what I've done. While it was turned on and I was probing for voltages on V5, the amp started making a terrible rustling crackling sound, and stopped when I pressed pin 5, the green wire. Just to make sure, I jiggled the wire again, and sure enough it started up again, it sounded like...
  11. S

    JCM900 4100 high plate voltage! Any help

    281v AC Volts
  12. S

    JCM900 4100 high plate voltage! Any help

    If this doesn't help I will try my hardest to get a picture..very difficult. What is the definitive answer that tell you my amp is definitely an EL34 model? Green wire comes from mains transformer pin 5, links to both capacitors and then to GN5 on pcb. Cap 1 (+ post red) Red wire to...
  13. S

    JCM900 4100 high plate voltage! Any help

    Here you go....Jon, you must ask me things in simple to understand directives. As you can see along the way, I have had some great advice, and managed to get the amplifier working with sound....of which it sounds great. So, I put the orange wire on the wrong pole to start with, I soldered it...
  14. S

    JCM900 4100 high plate voltage! Any help

    OK. So the B+ is 356V. I measured this at the first point of HT at the filter cap.
  15. S

    JCM900 4100 high plate voltage! Any help

    Sorry ..I had those values the wrong way around. It is -47V with the amp turned on in play mode
  16. S

    JCM900 4100 high plate voltage! Any help

    B+=356v
  17. S

    JCM900 4100 high plate voltage! Any help

    The voltages are -77v in standby and -47 turned on
  18. S

    JCM900 4100 high plate voltage! Any help

    The voltage in standby is -77V and turned on is -47V
  19. S

    JCM900 4100 high plate voltage! Any help

    .
  20. S

    JCM900 4100 high plate voltage! Any help

    Hi Jon. It is definitely an EL34 board and I have 34's in it. I've got 2 new filter caps and 4 new screen resistors in. I can't get the bias below 54mV. Do you think there's a possibility I may have to replace some of the other electrolytics? I'm using the proper octal bias probe to measure.

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