I would replace both those 7408s in that area. the chips I used are
nte7408. dont under etimate the power of the dark side (aka bad
traces) I scratched all the traces (on the top of the board) away from
the 2 7408s. You may want to replace the in line 10k? resistor
network to. the acid can get to that.
--- In PolySix@yahoogroups.com, "essboyer" <sean@...> wrote:
>
> Hi everyone!
>
> Just got into the exciting world of PolySix yesterday, when I was
> given two p6's for free!
>
> One is in great shape, though suffered some battery damage. the other
> is a near write-off with sever corrosion on several areas of the main
> boards.
>
> After repairing all bad traces and vias (AFAIK) on the good p6, and
> replacing the IC31 SN74LS08 with a SN7408 (note the lack of LS),
> things seem to only half-work.
>
> The sub-osc doesn't appear to work, the ADSR only sort of works
> sometimes, the effects don't work, but there is a slow delay that is
> constantly applied to the signal.
>
> The programmer does not function at all. Sometimes program lights 2
> and 5 will be on, other times just 3. Pressing any of the buttons on
> the programmer has no effect.
>
> I'm wondering if I really should replace the IC31 7408 with a 74LS08.
> The difference being that the LS has zener diodes, and different
> (higher?) impedance.
>
> Any suggestions on where to look next?
>
> Also, I believe the delay chips will need to be recallibrated. Are the
> trimmers on the bottom of each BBD section the bias or offset
> controls? OR neither?
>
> Thanks in advance!
>
> Sean
>