[Richard]

Here is the readers digest condensed version. The SCS units as built had a serious flaw with the control boards. Issue one was that the current for the compressors traveled through “lands”’ or circuits that were inadequate for the amperage. Second the connection to the board for the compressors was inadequate for a light bulb much less a compressor pulling almost 15 amps at times.

The first fix was to add external relays to remove the compressor current from the boards because at the time there were NO replacement boards to be had. https://newellgurus.com/showthread.php?tid=3252

In recent years Newell had someone make new boards that have robust connections and circuit enhancements. You really need one fix or the other. It will not increase performance, but will increase reliability.

Now let’s get to some basic troubleshooting. You say the breaker trips as soon as the AC comes on. Correct? If correct that tells us the problem is with the Number 1 compressor circuit.

Step one, disconnect all power, remove the circuit board and examine front and back for obvious circuit failure. Post pics of the front and back.

Step two, ohm the windings on the compressor, and both fan motors. That can easily be done where the connectors were removed from the board. https://www.mingledorffs.com/using-an-oh...-windings/

We can go further after seeing the results of those two.