Introduction
I purchased this untested English Commodore 64 from a local friend. Unfortunately, it booted to a black screen and hit my desk for repair. Interestingly, it passed all the diagnostic tests and would boot games from cartridge. However, when booting to BASIC it would yield a black screen.
Case Study
The first clue came from a wire dangling out of the back of this unit suggesting someone had modded it.
Inspection of the circuit board revealed a modded kernel ROM which became the first suspect as it certainly looked old and sketchy.
Replacing this mod with a known working kernel ROM fixed the issue and allowed it to boot BASIC.
Comments
You never know what you are going to find when you open a non-working c64. Fortunately, the kernel was socketed so this was an easy fix.