Discussion about the Korg PolySix synthesizer

--- In PolySix@yahoogroups.com, "wasteking1" <wasteking1@...> wrote:
>
> it appears from many recent posts that a very common issue with the 
> Polysix  after battery leakage is that certain LEDs stay on all the 
> time. Commonly the patch selection ones, but others as well. Now a few 
> people (including myself) have replaced IC 30 and 31  but this hasnt 
> helped. Aparrently digging out corroded traces doesnt solve the problem 
> either... Thus I will propose that the problem is UNWANTED 
> CONTINUITIES. 

It certainly can be, in my experience. All three boards I've worked on
had unexpected and in one case unbelievable "invisible" connections.

One point that might help a few people here: you can test for these
quite easily if you put IC30 and IC31 in sockets then just use a DMM
in resistance mode to test resistance to GND and +5V and between
adjacent data lines. Ensure that SIL resistor is really pulling up all
8 lines, for instance. On all the "unwanted continuity" lines I've
had, the resistance readings have been suspect. In one case, the
resistance readings fluctuated as if I was measuring a capacitor, in
this case the was a stray connection through the contaminated board to
a capacitor - I never found out which capacitor it was, I simply cut
the track and rerouted it with wire.
Just remember to put the new ICs in sockets, it saves so much time as
the resistance checks are more straightforward when the IC's own
internal resistance isn't present. 

>The pushbutton switches stay on..or is it that they are 
> bypassed and the LEDs light up because they get current regardless of 
> the switch position.  Can the battery acids, if they are indeed 
> conductive , actually soak into the plastic board? Would there be a way 
> to literally SOAK the board in a neutralizer that wouldnt hurt the 
> chips etc? any other thoughts?

I don't know of a way of doing this, but I also don't really see why
you'd need to as the total number of traces affected seems manageable
with insulated wires running above or below the board. The hard wiring
technique only works well if the damaged/shorting traces are isolated
or removed entirely.


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