I opened up a Marshall JTM50 and…..surprise! Rats Nest! The wiring is very sloppy and neatness does count for many reasons in an amplifier. It also had the output transformer replaced some time ago. The owner wanted to replace it with a Mercury Magnetics unit, replace the filter caps and clean up the wiring. In the end the amp looked better inside and sounded better as well. I’m more of a Fender amp guy but these early Marshalls do sound gooood!
I used some waxed string to bundle all the appropriate wires together. I also added screen and control grid resistors which made the amp sound and feel more stable. For some reason both types of resistors appear to have been removed.