[Early B.]

The power went out in my neighborhood for about an hour. The system was on when the power went out. While the power was out, I turned off the system. Once the power came back, I turned the system back on and there was a loud hum from the left speaker. I played some music and there was no music from the left speaker, just the hum. I switched speaker cables and the hum went to the right speaker. To rule out the preamp, I switched ICs and the hum remained on the left speaker.  Then I checked all of the fuses in the left amp and they look fine. I put my right amp in stereo mode and everything is playing fine, so I'm pretty sure the problem resides in the left amp. I have a SurgeX power conditioner, but I don't think it was triggered.

What else can I do to troubleshoot the problem??? 

[Folsom]

Does the amp have multiple fuses?

[Early B.]

Does the amp have multiple fuses?

Yes. It has one main fuse and several other fuses inside. I checked all of them.

[Mike B.]

Tube or SS? Did you test the fuses with a multimeter? It could be a tube if tube type.

[Early B.]

Tube or SS? Did you test the fuses with a multimeter? It could be a tube if tube type.

Solid state. I didn't check the fuses with a multimeter. Don't know how.

[Speedskater]

Then, I think that you need to find someone else to do the troubleshooting.

[richidoo]

Sorry to hear about your amp trouble, Early B.

I think you have troubleshooted it as much as you can without probing board level voltage and testing for blown output transistors. Running your amps in bridged mode pushes them closer to the edge and a voltage surge from the power outage probably pushed it over the edge while the other amp just lucked out this time.

Unfortunately, I think you will have to mail it back to the mfg for repair.

I would recommend that you install a whole house surge protector at the utility entry (meter) to avoid a repeat.
Good luck!

[SpatialKing]

Here are some ideas:
1.  I suggest you swap fuses with the fuses in the right amp that works properly, that will rule out the fuses as a problem. 
2.  Do you have the amps plugged into separate wall outlets?  If so, swap outlets.   
3.  Since you have the system plugged into a surge conditioner, remove it and run the entire system directly from a single wall outlet.  You may need to buy a generic power strip to get enough outlets.
4.  Assuming you can open your amplifier, remove power and all IC's, look inside, and look for something blown near the power inlet line.  You are looking for carbon, possible flash residuals, or something that smells not quite right.
5.  If all of the above checks out, then take the amplifier to a factory authorized repair shop and get a performance check.   As an alternative, if you know someone handy with an oscilloscope, have them check the amp with the inputs open and also with the inputs shorted.   If the amp has an hum issue, it will show up there.   

[SpatialKing]

PS:  I just thought of this - see if you can borrow an amplifier from a buddy and try that in your system.  That will eliminate any system related issues from the hum question.   So far, I don't see what you have done completely eliminates this question.

[Early B.]

OK, thanks, fellas. I'll take it to my tech guy next week.

[Don_S]

Solid state. I didn't check the fuses with a multimeter. Don't know how.

A blown fuse may not be visible. Checking with a multimeter is necessary. Just check for continuity. e.g. a complete circuit passing current. No value reading is necessary. The fuse either passes current or it does not.

Or, Drum roll please: swap the fuses from one amp into the other amp.

[timind]

If you're hearing hum, it's probably not a fuse issue. It would be better for you if it were. Good luck with it.

[rollo]

The power went out in my neighborhood for about an hour. The system was on when the power went out. While the power was out, I turned off the system. Once the power came back, I turned the system back on and there was a loud hum from the left speaker. I played some music and there was no music from the left speaker, just the hum. I switched speaker cables and the hum went to the right speaker. To rule out the preamp, I switched ICs and the hum remained on the left speaker.  Then I checked all of the fuses in the left amp and they look fine. I put my right amp in stereo mode and everything is playing fine, so I'm pretty sure the problem resides in the left amp. I have a SurgeX power conditioner, but I don't think it was triggered.

What else can I do to troubleshoot the problem???

   Did you smell any odors like wire burning ? You had surge protection ? Did not work ? Good luck.

charles