Vintage Synth Repair

Yea, its locked up for the most part.  Lfo 2 speed can still be adjusted immediately, but it seemed that after I wait a while the panel controls seem to unlock, its not perfect as it seems that the number select buttons only work 1, 6-8.  So 2-5 don't work.

Anyway, when I scope the reset inputs of the 3 CPUs I don't a locked voltage, which is normal.  When I power on the machine i can see the voltage jump as a spike on each reset.  So I'm assuming the reset works, as outlined on page 2b.

My scope is only a 20mhz but i can scope the other pins of the main cpu and i see what looks like all sorts of activity looks like pulse waves etc which I assume is normal.

I'm not so familiar with digital stuff, so i don't really know where to begin.  I was hoping when I bought this that it would just be a failed power supply!  Oh well 

Any further ideas? :)

greg

--- In vintagesynthrepair@yahoogroups.com, Malte Rogacki <gacki@...> wrote:
>
> So did I get this right:
> 
> At first the machine seems to be completely locked up?
> 
> Then after a while the controls (buttons, LED's and so on) start to work
> but there's still no sound?
> 
> There's one thing to keep in mind: The processors of the voice boards need
> their reset pulse, too. They are supplied with that pulse from the main
> processor board. So break out the oscilloscope and measure the situation on
> pin 9 of all three processors.
> If you have the service manual the reset procesure and the components are
> described on page 2b.
>