Overview
The Emulator II uses a third-party Compower switch-mode supply (not E-mu designed), and it is the single most common point of failure. Note: the EII has no backup battery, CMOS or NVRAM — all state loads from floppy at boot, so there is nothing battery-related to service here. Any guide telling you to replace a "PSU battery" is mistaken.
Common failures (gslug teardown)
- Vaporized tantalum capacitors, especially on the −15 V rail; tantalums can short −15 V to ground.
- Shorted mains rectifier diodes (two documented) → blown fuse.
- Shorted chopper transistor; dried-out electrolytics.
- Thermal design flaw: the 5 V rectifier diodes sit on heatsinks running ~60 °C and slowly cook the adjacent smoothing caps. The X2 mains caps are a known fire risk.
Recommended fix
Community consensus is to replace the whole PSU rather than chase individual parts:
- Abstrakt Instruments sells a drop-in replacement kit (based on a Mean Well RT-85C).
- DIY: a Mean Well RT-85C / RT-125B triple-output supply can be adapted.
If you insist on rebuilding the original: replace ALL electrolytics and tantalums, both mains rectifier diodes, the X2 caps, and verify the chopper transistor. Critically, confirm the +15 V rail is exactly +15 V before reconnecting the voice boards — an overvoltage event (e.g. +19 V) can destroy 7 of 8 SSM2045 filters at once.