Vintage Synth Repair

HI

thanks for the tip.. this is the second reply I have received 
mentioning the caps.. I will go and check those the next time the 
korg is in front of me

thanks again for the ideas!!!
-rick



--- In vintagesynthrepair@y..., "jdb000001" <jdb000001@y...> 
wrote:
> I've run across a problem in the past, with a piece of 
equipment that 
> used a single DAC fed thru a demultiplexer.  Hopefully it is 
similar 
> to your synth - I have not seen the schematic for the PS3200.
> 
> The output of the DAC is a sequence of voltages, generated 
from the 
> stored memory data.  The demultiplexer is used to send each 
of the 
> voltages to the circuit it controls, where it is stored on a 
> capacitor.  Since the capacitor discharges over time, the DAC 
> constantly cycles thru the sequence of voltages, recharging 
each 
> capacitor before it can discharge enough to be noticeable.
> 
> Now for the problem.  If one of the capacitors is leaky, or the 
> circuit it is connected to is discharging it, its voltage will drop 
> significantly before the DAC gets back around to recharging it.  
This 
> will cause a noticeable modulation in the circuitry it controls.  
The 
> voltage across the capacitor will appear as a sawtooth 
waveform if 
> you look at it on an oscilloscope.