Further Korg KR-55 notes...

I've had a few KR-55s in with the same fault over recent years... they're generally very reliable old machines but I've seen several that would power up but not run. The fault on all of them was a failed transistor on the logic board... the large 2SD288 (TO220) which serves as the 5v voltage regulator... here it is on the board...

...and here it is out of the board...

I'm not sure why this part has failed on a few machines, possibly, because of the weird angle it sits at, it may come into contact with the top pcb if it's not bent down sufficiently and create a short -  anyway, it might help if you've had similar problems with your KR-55... it's a very simple job to replace it.