Arp Odyssey troubleshooting

[RoutingChaos]

I've received this synthesizer from a friend who plugged in the power connector to the filter/adsr board the wrong way which resulted in no sound coming out anymore (big suprise here).
The way he plugged it in there was -15V on the ground rail and ground on the 15V rail. I'm quite stumped where to begin now though, would you just immediately replace all the active components or does anyone have a more elegant approach that I could try?

if anyone has any tips on how to approach this I'd be very thankful.
(I attached the schematics of the board below)


lilith

 

[ccaudle]

And +15V power was not connected anywhere? Was the device connected to anything else at the time? Was the power supply fully floating?
If the power supply was floating, and the device was not connected to anything else, then that would be the equivalent of just failing to connect the -15V supply, since there was still 15V between the positive rail and gnd, and in the proper polarity.
If for example the +15V was connected to the negative rail, or any of the DC coupled ports were connected to a different device that might change the analysis.

The general approach to start troubleshooting a possibly damaged component would be to power up the circuit from a current limited supply (resistors in the power rail connection if you don't have a bench supply with current limit settings) and measure all the DC bias points of the components. Look for transistors with base-emitter junctions not sitting around 0.5-0.7V, look for collector voltages that are the same as base or emitter voltages, on op-amps make sure that the inverting and non-inverting input are identical voltages to within a few mV.

I don't know what the component labeled 4023 is, and I can't quite read the marking on A2, but it looks like CA3080. I don't think CA3080 device are easily available currently, but you might be able to find a source if you need to replace it.
I'm not sure how you would diagnose whether the 3080 is working properly or not. It has a differential pair input, so I thought it would be connected like an op-amp, some feedback signal to pin 2, but that does no seem to be the case in the schematic you posted. Perhaps the gain is low enough that the device is run open loop, but since it has a diff pair input the constraint about input pins (pins 2 and 3) staying within a few mV of each other should still apply.

 

[JohnRoberts]

I would apply correct power and look at how it behaves. Looks like several cmos logic chips, an OTA, and a number of discrete devices.

JR