Archive of the former Yahoo!Groups mailing list: Discussion about the Korg PolySix synthesizer

Hello everyone;

since I wanted to get to the bottom of the capacitance problem with some
KLM367A clones I got me a dedicated capacitance meter and did some
measurements on various old and new boards. All measurements were done on
populated boards with the processor removed. I measured:

pin2 of IC22 socket to TP3 (that's essentially the capacitance across C22
to ground)
pin3 of IC22 socket to TP3 (that's essentially the capacitance across C23
to ground)
pin2 to pin3

I realize the absolute values probably don't mean too much; however it
should still be possible to compare the overall behaviour. The picture is
quite clear IMO.
All measurements in pF. The percent value is the difference between the
first and second column.


boardpin2pin3pin2<->pin3percent

old140.746.79214.7

old232.236.18918.3

new123.128.781.324,2

new22433.556.639.6

new2 (mod1)19.018.453.0-3.2

new2 (mod2)26.040.558.555.7


board "new2 (mod1)" has two 10p caps installed, "new2 (mod2)" has two 33p caps.

A couple of weeks my guess was that the difference between the two "clock
legs" becomes too great for some boards to properly function. The above
measurements seem to point into this direction as well. I have some more
half-finished clones on which I will do additionla measurements once they I
finished them.

I have no idea why the overall capacitance for board "new2" was
significantly lower than for board "new1"; I also don't know if this may
affect operation.

Ideas? Comments?