[sdiy] Keyboard controller question

[Gustav Andersson]

Hi
Some 2 years ago I built one of Ray Wilsons keyboard kontrollers ( 
http://www.musicfromouterspace.com/analogsynth/keybrdcontroller.html ), 
I never really got it to work properly then but after replacing a few 
broken ICs it now seems to be working fine except for one thing. 
Whenever I release the keys the s/h voltage drops half a volt or so 
resulting in the pitch dropping 5 or 6 semitones. 

I dont have scope at home but it seems I am getting a small pulse at the 
trigger input at IC3 (pin 13) that seems to discharge the capacitor 
slightly.
I'm powering the whole thing of +/- 15 volts instead of 12 volts which 
might screw things up.

I'm thinking maybe the delay for the trig pulse is to short so I have 
tried larger caps for c14 and c13 but that didn't help. Though I must 
confess I dont understand exactly how that part of the circuit is 
supposed to work.

Any suggestions are more than welcome.

/gustav