On Tue, 15 Apr 2003, Ellsworth Hall wrote:
> Hey all,
>
> I have a Polysix that I had MIDIed up back in '01. Battery was replaced
> 2 years before that. Worked fine until last fall when at first it
> wouldn't retain the patch memory settings, at least until it warmed up.
> Sounded like a bad IC32 SRAM chip according to the Old Crow.
>
> But now every time each patch comes up fine right away but now they
> can't be edited. So the patches now ARE being remembered correctly but
> can't be changed. ??????
>
> Is the board going up due to undetected corrosion (none visible since
> the battery change)? A different IC chip going bad? Any ideas?
Check to make sure IC25 (called a 4011 quad NAND gate) doesn't have
corroded pins or traces. A safe bet would be to replace IC25--this one
you can get at RatShak. IC25 disables writing to the RAM when the machine
is turned on so that random junk doesn't somehow overwrite the RAM
contents. This chip can fail in the same manner as the RAM chip, so
replacement is recommended, given that it is a 4000-series CMOS part and
it is 20+ years old.
Crow
/∗∗/