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View Full Version : Ampeg VT40 - need some technical help


sl1960a
10-19-2007, 03:57 PM
I just bought a clean Ampeg VT40 last week, but when I went to gig with it last weekend I had some problems. I powered it on and after warming up. I switched the standby off (lit up the standby light). I powered it down a couple of minutes later and switched my standby back on. For some unknown reason I switch the standby back off and the light lite up even when the power was off. Didn't think too much about it until gig time - when I went to power it on, it wouldn't - checked the fuse, it was popped. I put a new one in and powered it up, but when I went to take it out of standby, the standby light didn't lite and no sound (as if it was still in standby (the output tubes were on, but not lighting up brighter when you take a tube amp out of standby). I just popped the amp open and did a conrinuity check on the standby light - open.

It the standby light part of the circuit where if the light is burned out, it won't work? If so, can I gust bypass the light (jumper the two lamp wires together)? An advise or help would be appreciated - The amp rocked when I tested it and bought it, but I haven't got to jam with it with the band. :mad:

Leonc
10-19-2007, 04:28 PM
I've moved this to the correct section. Good luck. BTW, there are plenty of schematics available online. Try SchematicsHeaven.com for starters. You might be able to answer at least part of the question after getting a gander at the schematic...

BTW, did you test the amp at all before the gig?

sl1960a
10-19-2007, 04:41 PM
Thanks - No I bought it put in my van and pulled itout at the gig two days later. I've been seachin' the 'net - found a couple of threads that said it may be the 180K resistor in series with it. Any help would be appreciated!

Leonc
10-19-2007, 05:46 PM
http://www.kbapps.com/audio/schematics/tubeamps/ampeg/vt40.html

sl1960a
12-08-2007, 02:49 PM
FYI - got my vt40 fixed - bad filter caps. WOW this amp is a MONSTER!!

Leonc
12-08-2007, 06:35 PM
Cool. Congrats on getting a really classic, under-appreciated amp back in shape! Ya, the big electrolytic caps will always go, sooner or later and they make all the difference in the world.