From: user@example.net
I have a Korg SDD 3300 triple digital delay rack unit that was a bit of
a basket case when I got it. Someone had tried to "fix" it at some point
and it had a number of issues including the wrong voltage regulator
slapped in the negative rail, miswired output jacks, dead EL backlight,
bad SRAM 2032...
Fixed that up and I was able to get a copy of the service manual and use
the three-finger-salute button combo to get its mind back after SRAM
battery replacement as is common on units of this vintage, followed the
adjustment procedure in the service manual and everything seems to work
as it should now except one really irritating intermittent fault
remains: the LCD will occasionally garble up at power-on or in use as so:
It's annoyingly unpredictable and seems somewhat related to how it's
mounted? I can power it up 25 times on the bench and it works fine
making me think I solved the problem, then slide it back in the rack and
it starts acting up again. I've tried a number of things like adding
bypass capacitance on the display board which is separated from the CPU
by good distance, disconnecting the backlight thinking it might be
interference from the inverter, moving the wiring around, also recapping
the PSU which I was planning on doing anyway. Doesn't seem to help.
Here is the upper digital board (the analog board is on the lower
level), the lines to the LCD from the NEC Z80 variant are on the far right:
Thinking about just trying a new display with LED backlight at this
point but I've read that this unit can be finicky in accepting
aftermarket LCDs.
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