What does DRLC MAIN on a sony strd590 radio receiver?

DRLC (Different Room Link Control) which lets you setup an optional remote control receiver in another room, and connect it to an input jack (that doesn't exist on my unit).

If the receiver is played at maximum volume, it will go into protect mode. Heat has something to do with it, as does the output capacitors. If both A and B speakers are turned on, the surround sound must be turned off. If protect mode occurs when operating with a DVD, the sampling frequency may be set too high (which probably isn't the issue with our stone-age DVD)

This problem also occurs on my STR-D790. The problem occurred for us in the winter, and the house was 69 degF. The unit is in an enclosure that gets warm, but not hot, and the configuration has been the same for a long time. We don't operate the unit at high volume, and only the A speakers were on.

I'm guessing that the problem is that the unit contains aluminum electrolytic output capacitors, and that they are drying out with age and losing their capacitance. The problem is intermittent now, but likely to get worse. These devices are known to have a limited lifespan.

I have not attempted to repair it yet, but if you wish to give it a shot try the following:

1) Unplug the unit (duh) and take your time getting it apart so the capacitors have a chance to discharge. Remove the internal circuit boards that have large cylindrical aluminum things with markings that include "uFd" (microfarads). If any of those have tops that look like they have ballooned out, they are shorted and definitely bad, but that isn't likely in this case.

2) Short across the terminals of each capacitor for a few seconds to discharge them. They are like little batteries. If it isn't there already, mark the circuit board with which side is the "+" terminal, based on the marking on the side of the capacitor.

3) Unsolder one or both leads, and measure the capacitor with that setting of a DMM if you have one available that does that. If it measures to its rated value, its probably okay...for now. If in doubt or you don't have the equipment to measure them, replace all the big ones.

4) Take the board to Radio Shack or an electronics parts store and get replacement parts. Newark Electronics or Digikey is good too. The voltage rating of the new part can be greater, the uFD rating can be a little greater, but it still has to fit in the location.

This is obviously pretty deep DIY.