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Electronic & Amp guys - a solid state question


Billster

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I pulled my Marshall Valvestate out of the closet for the first time in maybe two years yesterday, and when I first turned it on, had NO SOUND.

 

After a few minutes, I had intermittent, staticy sound, and after about 20-30 minutes of the thing sitting there powered up, normal behavior.

 

My theory is that after such an extended off period, the capacitors had thoroughly discharged and needed to build up their load. Yes/No? If not, what is the reason for such behavior?

 

Finally, any downside to such an extended vacation for the circuit? Should I power up once a month or so, just for reliability purposes?

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I'd suspect the ON/OFF switch more than anything. Even the wires connecting the speakers. I'd also reseat the fuse. It shouldn't take long at all for the main power caps to charge.

 

As far as maintenance, solid state was meant to sit for years with no power.

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Bill, to the best of my recollection the caps should load up nearly instantaniously, unless they were bad when stored the unit and have a leak to ground. There's got to be something else going on.

As Prague noted, check all the connections, particularly any slide connectors. Sounds alot like a corroded connection that caused an open circuit and broke down in stages to finally let the current though.

 

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Even a tube amp shouldn't take more than 20 seconds or so to warm up after being plugged in. You should be able to store an amp for years without any problems.

 

As suggested above, I'd check for loose connections, corrosion, etc.

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What Prague, Dak, and Gabriel E said.

 

It sounds like a case of corrosion. The fuse is a likely suspect.

 

I've had this happen with battery operated devices where the batteries caused corrosion in their connection to the battery compartment leads. In that case a simple scratch with a wire brush, etc. cleared up the problem in a jiffy.

 

Capacitors will, indeed, power up in a tiny fraction of a second. I would expect a faulty, leaky capacitor to go bad long before you put the amp in storage.

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damn theres a helluva lot of things that could have gone wrong, none to do with the power side caps charging back up. That stuff happens in fractions of a second. I have worked on the Valvestates and I suspect one of those MMIC's (eight pin IC) in there that route rail voltage around might have not turned on right away. Probably had to heat up a bit. One thing about solid state amps is they benefit from reflowing the signal path now and again. Its the magic fixit that your local amp tech charges you $100 an hour for and you think he's great. I second the dirty pots, dirty input or worn input jacks. Theres a ton of stuff I could mention but without doing a check myself I couldn't reliably give you a sure fire fixit.
Down like a dollar comin up against a yen, doin pretty good for the shape I'm in
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