I have a problem with one of these amps, the SD500 un-boosted version (actually this is the second one I have the same problem with, and cannot return it, bought through ebay and seller does not want to communicate, etc.). The issue I have is the unit does not power on the actual amplifier part, through the DC DC converter (I have pulled the main PBC off and tested which component has failed). To provide an idea of what is happening, the unit shows the red power light, and when an LFE signal is passed to the unit, the power light activates, and turns green. From there on, there is no output to the sub, the internal relay does not activate, etc. I have checked all components and traced the issue to a small 8pin IC on the back of the PCB (side which faces the plate) location on the PCB U2. This seems to be a power management chip, which switches the actual amp part of the unit on /off. Unfortunately, the surface of the chip has been sand papered off (no chip identification marking left what so ever), and because of this, I am unable to see if I can find a replacement chip on the internet. I believe this has been done on purpose, although this is just speculation. There is also another chip on the same side, location U1 which has the surface of the chip also erased.
Now to my request... If anyone has pulled one of these apart, or is willing to help, I need the part of this chip (location U2). If the same is present on your model as mine (the chip surface has been erased), then I require the output of this chip, on each leg. This way, I might be able to locate something on alldatasheet.com.
I would like to thank anyone willing to assist me in advance.
Image of the location and chip...