Ok, two things.The mod wheel
I've resolved the strange mod-wheel issue where it seemed to have an effect on pitch bend and the data slider...
I calibrated it manually.
1) I unscrewed the assembly out and removed the wheel from the pot that controls the modulation; leaving the pitch-bend wheel alone.
2) With my multimeter, I measured the resistance of the pitch wheel while it was at rest in its center position. It read something like 4.32k
3) Then I adjusted the mod-wheel pot with my hand until it read exactly the same, 4.32k.
4) Put the wheel back on the modulation pot; making sure it was centered like the pitch wheel.
5) Plugged it back in, turned it on. The issue is gone. The problem doesn't show itself in the analog test procedure either.MIDI out
After looking carefully at the ESQ1 schematic at the buchty site, I was convinced I could remove the motherboard and positively test for a bad transistor. However once I started inspecting the motherboard carefully, I realized the schematics did not match what was on the board.
The labels for the components for MIDI out (and everything else) did not reflect that what was on the motherboard.
These ESQ-1 schematics did not match my board.http://www.buchty.net/ensoniq/files/schematics/esq1_digit1.gifhttp://www.buchty.net/ensoniq/files/esq1-tg/25.jpg
However, the labels on the SQ-80 schematics for the MIDI OUT components match exactly what I was tracing in my ESQ-1 board.http://memi.de/~buchty/ensoniq/schematics/sq80/sq80-d1.jpg
I tried to compare my motherboard with other photos of ESQ-1 motherboards and I can see the difference.
My board is labeled "Assembly ... revision J"
So the suspect transistor is NOT Q5, its Q1.
I used my multimeter's diode test and was able to see it was passing current from collector to emitter with power off. I believe that should not happen.
I will attempt to pull the transistor out tomorrow (Saturday) and replace it with a new.