Nakamichi Dac 101??

I just managed to get hold of a nakamichi dac101 12v for cars upon powerup into my home setup was quite suprised possible better than my own dac then music kind of skipped a couple of times and Silence????? dac has to led 48khz and 44.1khs it initially locked onto 44.1 and illuminated led now it flashes if you leave dac down powered for 2hrs it works for half an hour? I think its is a problem with clocks?? not v experienced in dig any one got any ideas???

by the way ps is 13.8 big fully charged lead acid:mad:
Does anybody have more information about this beast ? Schematics or service manual ?

I have found one off eBay and it seems well built but for the moment, lacking sufficient technical info, I am reluctant to dismantle or mod it.

The only schematic I found is partial and contains only a drawing for the output stage.