Re: K5 distorted output from patches using Source-2

Does this chip have a bias circuit to set the min/max
output voltage scale? It could be something as simple
as a cold solder joint finally loosing contact and
changing the bias. I'd check/re-solder the solder
joints to everything connected to the chip, and the
chip it's self.

James

--- narfman96 <narfman96-/[email protected]> wrote:

> 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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