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Marshall Valvestate VS65R
Posted: Sun Apr 10, 2005 11:08 am
by mui
Hi Anybody familiar repairing these? I've heard there are some design flaws in this design and I'm intrested what are the usual issues that makes this combo silent, (some IC's to mention or sthin), Powers up nicely and notices jack input but no CH1/2 lights go on and no sound. Tube lights up nicely aswell.
Posted: Thu Apr 14, 2005 7:52 pm
by Gtr_tech
Sounds to me like either no low voltage to the op amps/switching circuitry or the switching is section screwed. I believe there's 78-7915s in there to regulate the preamp voltage rails. You can check for proper output right at the pins of te reg ic's. Good place to start without having service info on that chassis.
Posted: Thu Apr 14, 2005 8:01 pm
by Gtr_tech
Sounds to me like either no low voltage to the op amps/switching circuitry or the switching is section screwed. I believe there's 78-7915s in there to regulate the preamp voltage rails. You can check for proper output right at the pins of te reg ic's. Good place to start without having service info on that chassis.