[sdiy] Juno 60 dead CPU diagnosis

Jack Jackson jackdamery at hotmail.co.uk
Sat May 9 17:33:35 CEST 2015

I bought a non working Juno 60 today. During the buy I popped the lid and found one cable unplugged and another cable in its place. I put them back in the right place but no joy.

Things I checked that work:
1. Power supply - Voltages are correctly adjusted according to service manual
2. Chorus - When I turn the chorus on I can hear it hiss as expected.
3. Output - Volume knob seems to work
4. Raw waveform - All show sawtooth at test point 3.
5. Patch LED display seems to allow you to choose different patches.

Things I checked that dont work:
1. VCA output
2. Gate output
3. Keyboard - keyboard seems to have no effect on raw waveform frequency at test point 3.
4. Test mode doesn't seem to do anything

I suspect it could be a dead CPU.  I tried removing the CPU chip and it seems to have no effect on the operation of anything that I listed above that worked - including the patch memory LED display.

Is there a way I could tell for super sure it is the CPU? If it is a dead CPU, what could have killed it? If it's dead where I can get a new one for cheap?


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