Vintage Synth Repair

--- In vintagesynthrepair@yahoogroups.com, Philip <eggwheatis@...> 
wrote:
>
> No problem...
> 
> Yes it's pulsing digital signals, and to check them 
> you need a logic probe or a scope. 
> 
> Then you can probe around the CPU to if you have the
> correct activity. A 4050 is a buffer chip..generally
> you should see the same signal on the input of the IC
> as on the relevant output.
> 
> Check that the cpu is not stuck in reset..the reset
> pin on the cpu should be high IE +5
> 
> Phil.

Very good info. 
The cpu pin 4 reads +5. 
After doublechecking, d17 (octave up) is conducting both ways, and 
(very much hopefully!) is what´s confusing the cpu. On Monday morning 
I´ll look for a replacement diode and will post the results. 

Paulo.