To see if the microcontroller is working you can do the following,
there is a 20pin IC 74HC373 (adress latch for eprom),
check if the DAC0832 does something,
measure pin2 at the TLC274 opamp.
look at the pins on these ICs if they are toggling around
with a "soundcard oscilloscope" for example:
http://www.zeitnitz.de/Christian/Scope/Scope_en.html testlead
<=------
| 100nF
1M pot | |<----| |------=> to soundcard audio in
|
_|_ gnd
But if the MIDI LED goes on, the microcontroller is probably working because the MIDI LED is controlled
by microcontroller pin14 via a transistor (siiting beside the LEDs).
damn, I don't have a dead one, somebody send me a dead one
low priced for a poor student for educational purpose only