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Marshall Valvestate 8080 has only 12V + and - on 15 volt rails, has a loud hum

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  • Marshall Valvestate 8080 has only 12V + and - on 15 volt rails, has a loud hum

    I am looking at a Marshall 8080 valvestate for a friend of mine. I checked the 15 volt rails and found one was -10.8v and the other was +14.3v. I checked the zeners and they are ok, only pass current in one direction, so I changed the 1000uF on the side with the low voltage. Now I'm getting 12.8 or 12.9 on both rails so I'm thinking it may be something down stream. Any help or ideas would be greatly appreciated.

  • #2
    Have you measured the ripple voltage? What is the zener value in the schematic. If I was shotgunning I would have replaced the zeners too.

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    • #3
      Why have you started a new thread on the same topic? It makes things very difficult for us.
      You should continue in the other thread here: https://music-electronics-forum.com/...ad.php?t=47630
      You said you were on a bulb limiter, if so, that is why the voltages are low.
      Please continue in the other thread which contains more information.
      Originally posted by Enzo
      I have a sign in my shop that says, "Never think up reasons not to check something."


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