Marshall JCM800 2204 Schematics
3x2AX7s, 2xEL34s, a solid state rectifier and a big transformer. Simple. If you like to turn up, turn on, ROCK then spend the evening nodding and smiling politely at groupies you can no longer hear this is the amp for you. Some would say one trick pony. I would argue no nonsense in an area where a lot of nonsense is spoken about presets and settings. It does one thing but it does it beautifully.
Ceriatone Marshall JCM800 2204 Layout:

Source:www.ceriatone.com
These early 80s models (with the vertical input jacks) use printed circuit board (PCB) construction to hold most of the components, but all jacks, pots, and tube sockets are mounted to the chassis and connected using wires.

Marshall JCM800 2204 Schematics
Marshall-jcm800-2204-Schematics