Hi fj bertrand,
By disconnecting the plugs you are talking about you would only interrupt the audio signal and not the power to the amps which is at the amps. You will need to disconnect them one at a time to see which one or both are shorted. If you need the serviced let me know. I stock most of them for exchange.

Cleeve Morrison
La Jolla Audio Repair

www.lajollaaudiorepair.com