Hi guys, My SC20H is not near the power output spec. It puts out may be max a few watts for switch in high and much less than 1W in the low switch position and guitar input connection. It is when both the Master and Pre-amp knobs maxed out. I checked EL34 plate voltage under 300vdc and it looks very low. I suspect some issues with the rectifier or PT. Can someone check Marshall's nominal bias voltages on EL34 of this amp. It would help a lot to track down the problem. Appreciate in advance.