[sdiy] FORMANT VCO restoration and improvement

[HA.Synth at t-online.de]

I am doing some restoration work on my Elektor FORMANT and started with the 
VCO. I have also done some improvement. So far i did:

replaced OpAmps to better types where appropriate.
Increase signal output to +/- 5V
Added voltage reference +/- 10V to critical points
Added sync input
Added lin FM
and some other minor changes.

Two Questions here

Now i want to add sync out. Therefore i wanted to use pin 8 of the 7413 
Schmitt Trigger. Just added a source follower here. But it didn't work. I 
can't see the pulse at the scope. Not at pin 8 nore at the output of the 
source follower. Any ideas or help here? Maybe the pulse is to short/weak to 
trigger my scope? Derive sync out from another waveform? Which?

The load capacitor and the transistor switch are driven against the +5V rail. 
Is it useful or recommended to put an +5V refernce here instaed?

Third Question: Any other iprovements?

Harald