Help repairing Sony ES-series car stereo?

Has anyone here repaired any of the Sony ES-series car stereos?

I'm trying to diagnose an XR-C750 head unit and would like some help.

Unit shows a display (clock) when the faceplate is attached. Pressing the
power (Source) button results in one beep (per usual) indicating power-on.
Then everything goes blank. Display flashes once per second, but never
reaches "booted" state. No sound from speakers.

Faceplate must be removed and replaced to cease the cycle of flashing.

If the power button is not pressed, I can sequence through -- and set -- the
parameters (clock, display contrast, etc.) on the faceplate (this is normal
function with power off).

Any ideas, suggestions, or pointers to schematics or other resources would be
greatly appreciated.

Thanks,
--
Dave C
dave-usenet3016@mailblocks.com