EMU SP1200 vintage drum computer. Device turned on, but did not load any sound or OS. The 5V voltage was clearly underestimated at 4.3V. The 5V voltage regulator measured around 100℃. Desoldering and testing under load the voltage still was still too low.
I replaced the faulty voltage regulator with a modern setp down regulator (drop in replacement).
That made the 5V rail much more stable and temerature is now around 25℃ instead of 100℃! Floppy disk drive still had no read / write function. I exchanged it against a modern HxC drive. I also detected Bouncing buttons. So all buttons were replaced with new ones (black ones were cleaned) and, in addition, all sliders were cleaned.
I’m documenting repairs for my reference and yours. I do synth restorations and repair with a specialty in vintage synthesizers, drum machines and other vintage gear, based in Düsseldorf, GERMANY