Discussion about the Korg PolySix synthesizer

Andrew;

your observations go along with my theory that this is a question of the
balance of the clock signals. By attaching the probe to C22 (or XTAL1 at
the chip) you increase the capacitance of C22 (which should originally be
10pF, not 22pF).
On the other hand I had decreased the capacitance of C23 (originally 22pF,
now 10pF but I first tested this with a 22pF and 10pF cap in series which
should give less than 7pF).

As I said earlier my measurements probably don't amount to much. I again
measured with the 10x probe setting. So even if we ignore the actual values
the following was still apearent:

- the signals on XTAL1 and XTAL2 are closer in amplitude on the old boards
than on the new boards
- exchanging C23 for a smaller value brought up the amplitude for XTAL2 on
the new board

All this was only measurable with the 10x probe setting; the measurements
with the 1x setting did not show such a strong difference (but they almost
always locked up the processor and showed a completely different waveform).
If I'm reading this right my probe has a capacitance of around 100pF in the
1x range and around 15pF in the 10x range - which of course explains why
measuring with the 1x setting does no good.

The new board with the different C23 value has been running now for over 12
hours.

I need to find out how to make screenshots from my scope (it's a digital
one); or perhaps I'll simply take pictures with the camera.