Fix protection mode on Denon DRA 395

A while back, my Denon DRA 395 receiver started aborting its power up cycle -- it would shut down automatically after a few seconds of blinking lights.  I put it aside (for nearly two years) and finally returned to fixing it recently.  After searching around a bit, I found a great hint in a video posted by databits about a Denon AVR-488 with similar symptoms.

The above video suggested a possible problem with the power regulators.  There are +/- 15V regulators (7815, 7915) located here in the DRA 395:

I checked the voltages at the outputs of the 7815 and 7915 with respect to the grounded heat sink.  In my case, the 7815 was fine.  However, pin 3 of the 7915 was around 0V, not at -15V as it should be.  The input voltage, pin 2 of the 7915, was at an acceptable -24V.  It looks like we found the problem -- time to swap the 7915.

The construction of the case makes it extremely difficult to get to the bottom of the circuit board for soldering rework.  I decided to cut out the old 7915 and solder the new one onto the old one's legs so that I could avoid case disassembly.

Extremely Important Note: The 7915 included with the DRA 395 had an insulated (plastic) heat sink, however most replacement parts in a TO-220 package will have the heat sink attached to pin 2 (-24V input).  You don't want to short that to the heat sink, so you will need to install the new heat sink with an electrical isolation kit (unless you can find one with an insulated heat sink).  You can see the insulating screw insert and pad behind the 7915 in the above photo.

I had some trouble in soldering the middle pin to the -24 V rail via the old 7915's cutoff leg, so I searched around the power diodes on the board to find another place to tap into it.  Here's how I attached it with an air wire:

Sure, it's a little ugly on the inside, but now my amp is ready for another decade of service!