Can anyone help me with diagnosing an electrical problem somewhere in my system?

Years ago, I had a McIntosh MC275 amp fail (under warranty) with a loud pop through the left speaker. The system went dead immediately but there was the acrid smell of burnt electronics. The company repaired it without issue and it has worked fine since then. However, for the first year or so, it always produced a slight odor. It finally went away. Apparently a tube shorted and destroyed a few components in the process.

I suppose the same is occurring with your repaired amp. If it is playing normally, I would give the odor a chance to diminish on its own. Of course if the odor is getting strong, I would shut it down and contact the repair facility at once to report the problem.

Hopefully not a problem!

Best, Fred

If nothing else was connected to that outlet other than the amps, I would look at the wall receptacle and see what sort of shape its in.

It could be a simple as a loose screw on the back of the receptacle, which could be heating it up.

Given that two different amps resulted in the same result, i would follow the aforementioned advice and check the outlet. Are you using the same aftermarket power cord? 

I used the same power cord run from the power conditioner. Since posting I tried it again and noticed the left channel is out. I am about to check the fuse inside.

Left channel out? Now a different scenario is presented- you may have a short on that channel- perhaps speaker cables touching each other, or a shorted woofer. If that is the case you may have damaged both amplifiers in the same way. This needs to be checked right away before any other amp is installed in the system!