I bought this 1983 2203 100w head for dirt cheap, but as I opened the hood I was rewarded with a messy inner arrangement, swollen electrolytics, inductors in rlc circuits behind every pot, a ton of relays, 2xel84+2xel34, chassis holes back front and center … your typical ultra modded shit. I had initially tabbed on a simple revamp – the clean channel sounded really nice and sparkly – but had to give up on the idea given the timeline.
After some work I was able to get this powerhouse back on the up and up. Bellow is a gut shot of the amp as it stands today, in stock circuit configuration with a brand new ptp board, a couple more Orange Drop 715 caps and the original Marshall resistors, possibly carbon film. I ungrounded the pots as advised.
I also added the compulsory PPIMV and it sounds dope!! The amp is a wet dream for stoner guitarists, fat, greasy, sharp. A surprising amount of gain is on tap… obviously the PI tube acts as a low impedance symmetric extra-gain stage without any of the inconvenient of the added gain stage before V1a i.e. hum and other high-impedance related niceties.