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Topic: peavey nashville 400 comp light and howl- only on a gig |
Lynn Kasdorf
From:
Waterford Virginia, USA
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Posted 12 Sep 2010 7:45 am |
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I did an important (to me) gig last night with my old Nashville 400- at least I tried to. I tried this thing out at home all day- played loud- and it worked fine.
Got all set up at the gig- everything was fine. First song kicks off, and as soon as I try to play something, the yellow comp light comes on, and then the amp starts "screaming" or "howling". A horrible, loud sound that it does on its own.
Luckily, I had also brought my nashville 112 and was able to run out to the car, get it and be all set up before the next song.
I know I can send the chassis to Peavey and have it gone over for $250 (right?), but maybe somebody as an idea here. I'm an electronics guy and I'm good with a soldering iron. Maybe it has a cold solder joint and I should re-melt all the soldered pot and jack connections. But then, how do I test it without trying it on a gig?
This was my main amp before I got the nash 112. Last time I used it on a gig, we played a telecaster through it and it worked ok except for a bad input jack- had to wiggle the plug to get it to work. So, before my gig I took it apart and cleaned an retensioned the input jacks. All seemed well.
What I find amazing is that this problem only happens when the ambient sound level is high! Like during a song on a gig. Works fine in the living room. Gee, that's handy...
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"You call that thing a guitar?" |
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Mike Wheeler
From:
Delaware, Ohio, USA
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Posted 12 Sep 2010 8:15 am
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I would suspect the A/C voltage was sagging. I've had this happen at gigs. Sound check is fine, then all he!! breaks loose at show time.
On the other hand, your 400 might need new power supply caps. If they are still the original ones, they likely are loosing their ability to filter the DC reliably, so internal voltages can drop lower than the amp can tolerate. In the worst case, the caps can short out internally and explode...usually taking other components with them.
Combine these two situations and the 400 can go nuts.
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Best regards,
Mike |
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Lynn Kasdorf
From:
Waterford Virginia, USA
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Posted 12 Sep 2010 8:26 am
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| Mike Wheeler wrote: |
I would suspect the A/C voltage was sagging. I've had this happen at gigs. Sound check is fine, then all he!! breaks loose at show time.
On the other hand, your 400 might need new power supply caps. If they are still the original ones, they likely are loosing their ability to filter the DC reliably, so internal voltages can drop lower than the amp can tolerate. In the worst case, the caps can short out internally and explode...usually taking other components with them.
Combine these two situations and the 400 can go nuts. |
The gig was at a pretty old dive with marginal wiring, so AC sag could be an issue. And the caps are old for sure. Maybe I can re-create the problem on the bench by running it off a variac and see if the problem happens.
Actually, if I replace the filter caps, I should bring up voltage gradually with a variac anyway, right? Or is this just with tube amps?
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"You call that thing a guitar?" |
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