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Temp "Time Format" issue Fix in Discussions

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Author Topic: MP-1 loud buzz  (Read 5305 times)

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j_weeks

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MP-1 loud buzz
« on: Time Format »

I just picked up another MP-1. The unit works fine for the first 1-2 minutes, then after it heats up i start to get a loud buzz/hum. I put new tubes in it and noticed that one of the tube sockets was slightly loose, but both tubes still light up when powered on. Has anyone experienced this problem before?? :???:
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j_weeks

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Re: MP-1 loud buzz
« Reply #1 on: Time Format »

Heres a video of what the preamp is doing. https://www.youtube.com/watch?v=tAgtZCMz-UQ
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j_weeks

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Re: MP-1 loud buzz
« Reply #2 on: Time Format »

Hell I think I found the problem. One of the caps looks shot.
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rnolan

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Re: MP-1 loud buzz
« Reply #3 on: Time Format »

Mmm, it's not looking like a happy cappy, and you may well have located your problem (and hopefully that's all it is)
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Studio Rig: Stuff; Live Rig: More Stuff; Guitars: A few

MarshallJMP

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Re: MP-1 loud buzz
« Reply #4 on: Time Format »

Yes seems to be shot,replace all 3 (black) caps while you're at it.
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j_weeks

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Re: MP-1 loud buzz
« Reply #5 on: Time Format »

I replaced all 3 caps on the tube board (6.8 uF 450v) and she's back and running perfect. No more hum :banana:
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MarshallJMP

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Re: MP-1 loud buzz
« Reply #6 on: Time Format »

Ok great to hear!!
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rnolan

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Re: MP-1 loud buzz
« Reply #7 on: Time Format »

I replaced all 3 caps on the tube board (6.8 uF 450v) and she's back and running perfect. No more hum :banana:
:whoohoo!:
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Studio Rig: Stuff; Live Rig: More Stuff; Guitars: A few

gb

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Re: MP-1 loud buzz
« Reply #8 on: Time Format »

So by caps you mean capacitor?  And how do you know if they are stuffed by looking at them?
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j_weeks

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Re: MP-1 loud buzz
« Reply #9 on: Time Format »

Correct gb. If a capacitor is swollen out on top, or busted open as in the case with my mp-1, it is an obvious sign that the capacitor is no longer viable. That is not always the case though, some bad capacitors show no signs.
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