1984 Marshall JCM 800

This classic British amplifier needed a full re-tube + bias, cap job and general cleaning of pots and hardware. It was completely original with the exception of modern power tubes which had blown. The original LCR brand filter caps were still in place and as they started to fail with high ESR value they took out the 6550’s and the HT fuse. The filter caps were changed to German made F+T caps and the bias caps were replaced with Sprague Atoms. The tubes were replaced with JJ 12AX7’s and a set of JJ 6550’s (much better than the Groove Tubes that had come with the amp). The Fixed Bias was set to %63 Class AB Plate Dissipation with a B+ of 446VDC. One of my favorite amps to work on.