[sdiy] Frozen DX7IID

[greg at gzifcak.net]

Hello,

I just replaced the RAM in my DX7II. I swapped the existing Toshiba
TC5564PL-15 chips for TC5564APL-15 since this is all I could find
available. I searched for info on the meaning of the suffix but couldn't
find anything.

Anyway, I did not try powering it on before I did the repair, but it
worked fine (aside from the RAM) when I last used it about a month ago or
so.

When I powered it on after replacing the RAM chips, all lights came on and
the screen is blank except for the top row, which is showing solid bars.
It is making no sound and no panel controls have any effect.

I probed around with my scope and the sub-CPU and main CPU are both
receiving clock and show approximately 5v on the power pins.

Any ideas what else to check or should I hunt for replacement CPUs?

Thanks in advance,
Greg