PM 1.5 that just won't quit--turn off

I have a bunch of PM 1.5 amps and have encountered one that does not want to turn off via the Power and Sequencer switches on the front panel. I checked both switches with a meter and they are in proper working order. The amp functions fine otherwise, but must be turned off by unplugging or turning off the power source. Any input appreciated...

Strip plug or line conditioner for an easy fix.

I use sequenced power conditioners for all of my amps, but the objective here is not for it to work, but to work CORRECTLY--I'd like to find the source of the problem and fix it. A lot of amps use relays on the power supplies that may become sticky or burned, but this is not the case with the PM 1.5 amps.

Thanks anyway...

Check the power supply Triac if it's shorted.

Holy Thread Revival, Batman!

I was reading through some of the old threads and saw another older post similar to this. Anyone that has a PM1200, PM1.5, PM1800, PM2400 etc. That doesn't power down, I would advise getting the amp in to a qualified service shop. If the transformer phase control triac shorts , then the transformer runs hot and the rail voltages are elevated too causing more heating as well as stress on the filter caps and power transistors. Some people replied to continue using it the way it is, just pull the power plug to power it down; but I wouldn't advise doing this for the above reasons.