#1
Hey all. I have a problem with a Marshall Valvestate Amp I just picked up off a guy. Couldn't test it on pickup. Got it home and I turn it on with nothing plugged in and there is a pretty good HUM happening. I notice the hum will go away it seems when put my fingers on the faceplate, or if I lean the amp forward. The hum gets louder if I touch the mesh screen covering the speaker. Seems like a ground hum? Anyone have solutions?
#2
I would unplug it and not turn it on until you know more about what is going on.
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#3
Quote by trashedlostfdup
I would unplug it and not turn it on until you know more about what is going on.


I love it when people post useful information It's not like the AVT is gonna explode, that said if you got it for some crazy cheap price and couldn't try it out... well the guy could just be a massive dickhead.

Check the kettle lead, try a different one

Check your guitar cable, try a different one

Try a different guitar

Try the amp on a different mains power socket

If all that fails, well at least you've tried all of the super cheap options for fixing the problem. Take it to a guitar store and get them to look at it, they're likely to be able to help diagnose the problem if they're at least half decent. If it is a grounding problem that's not too much of a big deal, but the main thing you should take away from this is that you should always, always, test gear out when it's second hand - and be thorough about it.
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#4
Yea, I'm not taking it to amp repair specialist on something small and drop another bill on it or more. I know how to wire and I don't think this is a big deal. Also amp making sound with nothing plugged into it.
#5
Quote by reelbigfish2020
Yea, I'm not taking it to amp repair specialist on something small and drop another bill on it or more. I know how to wire and I don't think this is a big deal. Also amp making sound with nothing plugged into it.


I meant that just taking it into someone more experienced means they could spit ball ideas on what the issue could be; rather than being 'well, I have ideas, but it'll cost you!'

Try rewiring the ground and see if that fixes it, if that's not it maybe there's something wrong with some connectors in the inside, or the amp is just towards the end of its life (I wouldn't pay to repair it either)
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Korg AX5G
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Zvex Fuzz Factory
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#6
Not that this "IS THE ISSUE" mind you - but, I did have a Tube Amp that did the same thing - sort of. One of my pre-amp / Pre-gain stage 12AX7's was shot. The tech identified it quickly because my amp has two inputs, high and low, and the high gain had the hum. Because, it has an extra 12AX7, and that was the tube that was shot. I replaced the tube, and blam-o - good as new.

I know the Marshall Valvestate's have a tube pre-amp - so maybe, just maybe it could be that? Not saying it is, but i suppose it could be - still doesn't make sense that it goes away when you touch the face-plate. That really does sound like a ground issue. Still, I thought I'd offer, on the off hand chance that maybe that was it.

This website might also offer some help - http://www.geofex.com/ampdbug/hum.htm
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Last edited by Jonny Ryan Mac at Jul 15, 2016,
#8
Nice! - that was my issue as well - good to know sometimes its a simple solution!
1981 Gibson Les Paul Custom (Black Beauty)
1980 Marshall JMP 2204