K5 distorted output from patches using Source-2

Hi, 
I've been troubleshooting a neglected K5 I found. I replaced the 
battery. Fixed a missing ground trace on the mix output. Verified the 
power supply voltages. There are a few keys that are hit and miss. 
Etc.

The output whenever the S2 source is included in a patch is cranked 
and distorted. If I set the S1/S2 balance to -31 I can hear S1 at the 
normal volume with no distortion. As soon as the S2 source is mixed 
in even at -30 the distortion appears. At 0 to +31 it turns into a FM 
and ring modulated mush fest. It sounds analog to me. If I turn down 
the harmonics in the DHG for S2 to around 30 or so the distorion goes 
away. So it seems volume related.

Using only a DVM I traced out the JRC opamps and they are working 
fine except for the clipping in IC9 on pin 7. Then I noticed the DAC 
output for IC14 is 2 to 3 times higher than IC15. I can vary these 
outputs with the balance as S2 is IC14 and S1 is IC15. Could IC14 the 
Burr-Brown PCM55HP DAC have failed and be causing this distorion? 
This is the first analog section in the synth. The only doubt I have 
is can the Kawai digital chips when they fail overdrive the DAC's 
capabilities? Doesn't seem like they could or if this did happen it 
should sound digital. Eh???

Sorry for the lenghty post. I don't have the Service Manual or a 
schematic for this puppy. I need to find one and I've already signed 
their disclosure form. This is a V1.0 K5 and next I will make a V1.3 
27C512 eprom for it. What's the 27C256 for, harmonic tables?

Thanks for listening, Fran   


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