Vintage Synth Repair

Hi,

Thank you for replying.

I checked the ICs that you mentioned and they seems to be working fine.

What I don't understand is that the KBD Track signal enters at the input pin 3 of IC23 multiplexer and should come out at each output but it's just not there for 2 outputs.

Like I said, I already replace the buffer chip IC21 for those voices and that did not help.

Any other ideas?
Thank you!


Nicolas

--- In vintagesynthrepair@yahoogroups.com, Malte Rogacki <gacki@...> wrote:
>
> If single voices are affected the problem never resides with the CPU board.
> Problems with the CPU board affect all voices identically.
> 
> So we have various parameters that affect Cutoff. Most notably of course
> cutoff/cutoff mod (this CV contains als the LFO modulation if applicable);
> then we have the external filter control. Those two affect all voices
> globally.
> Then we have key track and EG intensity; those affect individual voices
> (since the effect they have on a single voice depends also on the pressed
> key and on the point the envelope has reached).
> 
> So if key track has no result for certain voices I would see if the
> keyboard CV reaches this part of the circuit. This enters on pin 3 of IC
> 29. Check also the buffers between IC 29 and IC 25. Also, the buffers
> behind IC 23 could also affect Cutoff in general.
>