[sdiy] midi keyboard failure

[o b i s : c y g m a]

Hey guys, I've had this Kaysound MK-4902 that's been acting up lately.

It will not power-on under A/C adapter juice or battery-power. Although,
after I took it apart and disconnected the keyboard assembly from the rest
of the unit, it would power on fine... all top-panel buttons responded
properly and the little LED display seemed to be indicating that the unit
was working correctly.

But when I re-attach the keyboard assembly, it again fails to power-on.

I have no schemos for this, and even less patience (which is why I refuse to
send it back)...

A few other pieces to this puzzle:

About 24-hours after I got it, the supplied AC adapter suddenly died.

I obtained a radshack one, and that was fine for several months. Then, after
the unit had collected some dust for a while, I tried to fire it up again,
and it came on, but seemed to "crash"... there was no MIDI output, and the
function keys (channel select, etc) were ineffectual and the LED display was
"frozen"...

Any suggestions on how to go about trouble-shooting this or further
isolating the area of the problem?

Thanks!
  obis