1990 Marshall JCM 900 2500 MK3

This amp needed a complete cap job in the power and signal sections, all new tubes, the bias C- voltage modded to provide correct biasing of the EL34/6CA7 power tubes and general cleaning + pots sprayed out (A lot!). Also the V2 tube socket had to be replaced with a new 9 pin socket of higher quality as the old one was dropping voltage to pin 8. The preamp sockets are riveted in place so I had to take my grinder to it for removal - fun stuff, thanks Marshall! The pots and sockets are a weak point of this series.

2 of the preamp tubes were NOS RCA blackplate and greyplate 12AX7’s, 1 TAD ECC83CZ selected for the cathode follower, and the power tubes were NOS CBS/Hytron 6CA7’s. The caps were a mix of Vishay, F+T, Sprague, IC, and CE brands. Finding all the correct values takes a number of different brands these days to get right. The Fixed Bias was set at %66 Class AB Plate Dissipation. This particular JCM 900 was the best sounding one I have ever heard.