Hi guys, I am working on a Marshal 1974X-20-20 reissue 18 watt tube amp hand wired point to point. http://www.ampwares.com/schematics/marshall/marshall_18watt_schem.pdf Capacitor C3 connected to the cathodes of the EL84's has a stated value per the schematic as 50-500uf/50V. The actual cap in the amp measures 439uf and is marked as 470uf 100V. What does the 50 indicate? This cap and a 125 ohm 5 watt resistor (resistor in the amp measures 107 ohms) are in parallel and control the bias. Just as a side bar, there are other things on this schematic and actually installed in the amp that I don't understand how it is possible that they could actually work. Looking at the Normal input J1 Low and J2 High both have a 1M resistor from the positive input to ground and on to the grid of the 12ax7. This resistor would have the effect of creating a large impedance mismatch which would limit the current to the tube. If one wanted to have a low gain and a higher gain input how is it possible that the two resistors could have the same value? Signed....confused in Miami...again...lol Billy Edit...One other clue is that there are 50uf 25V caps indicated which says to me a value that has not been made for a good many years....47uf yes...50uf no. The actual value printed on that cap is 22uf 100V, so there are things on the schematic that do not match what what is in the amp in the first place.