500/5 LF channel problems

Will be no doubt the main power amp that has failed that is connected to that channel. It will be located on a big heat sink and be hotter than the other(s) channels if you go in after it's been on.

If the sound is also dead on that channel on a pair of headphones. Then you have probably lost the main power amp for that channel. To be certain. With you headphones on, slide or turn the balance control so you can only hear the faulty channel. With some music playing turn up the volume. If you can hear "faintly" music playing then the pre-amp is OK and the power amp has gone.
The power amp will be located on a heat sink. It will consist of 4 transistors (2 for each channel) or one big device (or two) (an IC). If it is transistors you only need to replace the two for the right channel.

This sounds like it could be an overheating issue. Some manufacturers use a cheap thermal paste on their processors. If you are dealing with a computer this should be an easy fix but if you are dealing with a laptop then it is much more involved. Go to Youtube and research replacing or removing heat sink. You wont be replacing the heat sink but the procedure is the same except you will need to clean the old paste off your heat sink before you apply more. Don't go crazy with the paste, a little goes a long way, all you are doing with the thermal paste is ensuring full contact between the processor and the heat sink with no air gaps.

Power supply in most cases and a lot of the time the part is under a heat sink where you cannot see it.

You might have more help if you posted the question again with the exact brand and model number.......

I believe you popped your breaker at the box. If it does not reset then you have to replace the breaker itself.

The Thermal Senser on the Heat sink may be Defective. Heat the Thermal senser and see if Fan Turns on. It is a device with 2 screws holding it to the heat sink

There are so many components that can fail that troubleshooting this can be an expensive problem.

HINT: Put a 150 Watt light bulb in series with the power going into to limit current for/during troubleshooting.

Go through and compare the voltages on the teo channels. If power amp transistors have failed, likely the driver transistors also are gone.

Testing components in-circuit is very dificult. Resistors are pretty reliable and usually show damage by discoloration.

Furhter use before repairing MAY cause further damage.

The heat sink has the power modules attached but also has 2 power transistors that become disconnected from the circuit board when the heat sink moves or flexes. The pins on each need to be resoldered (it helps to bend them a bit too, prior to soldering). Had the same problem on the same amp today and that was the fix. There was no sound other than a clicking when the volume control was rotated.

Remove the heat sink and fan, take it to any computer shop and they will give you compatible replacements

More than likely, you popped an amp channel. My experience is that it is the one closest to the middle of the heat sink.

Take it to an authorized service center, and be prepared for a large bill. Good luck...Rob