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Marshall valvestate 40 guitar combo, clean channel works fine, dirty channel has no o/p have changed valve ecc83, channel indicator led comes on and valve lights up but still no o/p. Can you help please Andy

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Hi Andy

The problem you face is most probably the same that stops most all valve state amps from working. They suffer terribly from fry/cracked solder joints. You will have to remove the main circuit board from the chassis, and resolder any suspect joints you can see, particularly about the rear loop in out jacks, control pots on the front panel, and power supply. There is a large power resistor and zener diode that cause problems in this model from memory. The valve never fails in these amps. Due to the lower supply voltages they are run at, they are not under alot of pressure, and as such give good reliable service. Go over the amp for dry joints first, and see how you get on. I have repaired so many of these with that problem.

regards
robotek

Posted on Nov 08, 2008

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