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  1. R

    Marshall JMV410H

    One step closer. Connected a cathode current meter to the tubes. Measured about 40mA. Then the current started to rise on V3 and V4 to about 50-55 mA. The pop sound came and the cathode current dropped to about 40mA. After a while it rose again and the same thing happened. V1 and V2 were normal.
  2. R

    Marshall JMV410H

    I have just put in 4 new tubes
  3. R

    Marshall JMV410H

    Having a strange problem with a Marshall JMV410H. At irregular intervals there is a pop sound. The sound is the same as when you switch off the standby button. Like a small pistol shot, but with a silencer. Several minutes may pass between each time it happens. All volume controls are set to...
  4. R

    Popping sound marshall jvm410H

    I will take a look at the tubes. To make it clear. I changed first the two catode resistors and then a put in the new tubes. i will also check the screen resistors.
  5. R

    Popping sound marshall jvm410H

    The popping starts after changing the tubes. That is what the owner said. I could not try it before, because of the burned resistor.
  6. R

    Popping sound marshall jvm410H

    I have changed the 4 power tubes and also the two cathode resistors with the same value but as 3W. One was burnt. Have also adjusted the bias to approx. 45mA for each tube (pair). Might try to test with one by one of the old pipes to see if that helps.
  7. R

    Popping sound marshall jvm410H

    I run a small service workshop for electronics, especially tube amplifiers. I have received a Marshall JVM410H which emits a pop sound in a non-linear pattern. There may be pop sounds at 40 second intervals or it may take up to 5 minutes before the sound comes. The sound does not depend on the...
  8. R

    Marshall Super PA 100

    Thanx. I will check the voltage loss and the ESR. And will use a variac to check the curent. I also uploaded a picture in higher resolution. I understood that the owner would like to have the amp so close to the original as possible.
  9. R

    Marshall Super PA 100

    Ooops. Forgotten serial number. It says SP/4700A
  10. R

    Marshall Super PA 100

    Hi I have a Marshall Super PA 100 with serial number to check for a customer. For me it lokks like there are original capasitors in the amp. See pictures. Is it necessary to change this capasitors? There are no leakage or "bubble" .
  11. IMG_20220117_192303

    IMG_20220117_192303

    • rbotn
    • Media item
    • Comments: 0
    • Category: Marshall Amps
  12. IMG_20220117_192227

    IMG_20220117_192227

    • rbotn
    • Media item
    • Comments: 0
    • Category: Marshall Amps
  13. R

    Fire in Marshall2203

    Hi I got an amp Marshall 2203-1 with effect card from a customer who has burned. As you can see at the attached pictures it is R31/32 in the filament system, and R17/18/20 in the feedback/cathode of the phase inverter tube, and R11 the cathode resistor at V2, the second valve in the preamp witch...
  14. R

    Hum and hiss Marshall JCM 800

    Thanx for lot of tips. i will try some of them this week-end and report back the result. @neikeel asked for what happened . The owner told me that he tried to adjust the bias, then he short-circuited two pins on one of the EL34. @Ray Baker. I am using a variac with ground between the wall and...
  15. R

    Hum and hiss Marshall JCM 800

    Thanx. Now it is public
  16. R

    Hum and hiss Marshall JCM 800

    Hi everybody. I hope that somebody can help me thinking. I have looked at this amp for a while, and I have problem thinking rationally. I have uploaded a video who explain the problems with the amp. I think it is a grounding problem, I have checked all point of soldering, twisted the filament...
    • rbotn
    • Thread
    • artiste filament hiss hum jcm800
    • Replies: 8
    • Forum: The Workbench
  17. R

    JMC 800 Artist (2203) with noise

    Yes. I have also a suspicion about ground, but it looks like every groundpoint is ok. I have changed the preamp tubes. No difference When I remove the first preamp tube, the noise is almost gone. Even when the guitar volume is totally down, the noise is still the same.
  18. R

    JMC 800 Artist (2203) with noise

    Sorry. had forgotten to set to Publish. Thanx.
  19. R

    JMC 800 Artist (2203) with noise

    Help! I have a Marshall JCM 800 who are rather noisy at High input. I post a video here where you can hear the noise when I put in the guitar at high input. I have tried with 6,3 DC filament for the two preamp tubes, no result. I have change the jack input set at the front. In the video you can...
  20. R

    Noisy JMC 800 Artist (2203)

    Hi. I wonder if I have the right diagram, because there is a effectloop printboard in the amp. I put a picture inside the amp. I also put a video about the noise when I connect a guitar to the High input. Also there is a vlip from the scope at the end of the video. The probe is connected to...

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