[sdiy] Juno 60 dead CPU diagnosis

rsdio at audiobanshee.com rsdio at audiobanshee.com
Sat May 9 18:59:31 CEST 2015


My quick skimming of the Juno 60 Service Manual shows that there are two CPU chips. Which one are you referring to?

Is there one of those CPU upgrade boards installed that might be replacing one of the CPUs?

Grab the Service Manual online and go through the adjustments section. It has expected waveforms that you can check with a scope (or maybe even an audio interface, if you make some probes with audio wires).

Brian


On May 9, 2015, at 8:33 AM, Jack Jackson <jackdamery at hotmail.co.uk> wrote:
> 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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