1989 MARSHALL JCM 800 2210

This is the Switch-Channel 100 watt Reverb version of the famous JCM 800. It has the ability to switch between a piggy-backed boost circuit or the cleaner and more straight forward “clean” circuit. The clean channel is differentiated with the more concise Treble/Bass tone stack - although this tone stack is unlike any normal Fender/Marshall/Vox circuit. In fact it is very unique, Marshall themselves never used it again in any of their amps. The reverb is definitely a different vibe than the Fender style circuit being darker with a shorter decay and far more subtle. This amp came needing a standard workup, having never been previously repaired.

The amp was given a full restoration. All the axial lead electrolytic capacitors were replaced with upgraded temperature rated Vishay/MOD/CE brand electrolytic’s. The multi-section cap can’s were replaced with new German made F&T 50/50uf 500v type units. The power dropping resistors were upgraded to 3 watt Metal Film type and the Screen Grid resistors were upgraded to 5 Watt Cement type units respectively. This was done for better noise floor and reliability. The diagnosis was blown power tubes, burned open screen resistors, and swollen filter caps with high ESR ratings.

To any one on the internet that say 30+ year old amps don’t necessarily need cap jobs, take a look at the photos below of the 34 year old cans. The caustic paste inside is pushing up through the exhaust port in the center bottoms of the LCR cans - it can also be observed that the cans have swollen around the metal bands that hold them in place. This means they are bad and will eventually explode on the inside of the amp causing the power tubes and power transformer to very likely fail. They looked okay from the outside - and this is why amps of this age always need restorations, even if from a casual glance they look fine or even play fine, they should be brought to a competent tech.

The amp was completely re-tubed with the following compliment. V1-V4 = JJ 12AX7S, V5 = EHX 12AX7, V6-V9 = JJ E34L Matched Quad. I picked out this lineup specifically for this amp to give the best balance of tone, reliability, and low noise. The adjustable Fixed Bias was set to %68 Class AB Plate Dissipation with a B+ of 422 VDC. All pots were cleaned and hardware tightened.