Discussion about the Korg PolySix synthesizer

In recent years I've noticed that my P6 takes quite a while to to warm up and get in tune. I read some older posts here and it sounds like 10 seconds is normal. Mine takes longer, maybe a minute, but it's more like a slow VCO LFO rather than individual notes being out of tune. My gut would tell me to start replacing capacitors but I haven't pursued it and I'm not sure how it would affect the sound by doing that.

Also - generally speaking the synth out of tune and is off by a semi-tone or so. I've got my tune knob all the way to the left and I imagine it'll get worse over time. Note for note the synth is ok so the calibration appears to be normal, but as I said, overall it's noticeably out of normal range.

Thanks everyone!
(Hammering you guys with questions today) :)

One observation which might be worth considering before you do anything else
and that is make sure the PSU is generating clean DC voltages to the rest of
the P6, calibrated and within spec. You will need to consult the service
manual and someone who owns an oscilloscope to get this right. Settings
drifting over time and logic randomly latching is never a good sign.
However, if it is just the MG which goes crackers then make sure the MG rate
pot reliably delivers between ­5 and +5 volts when fully clockwise. Give it
a good waggle! Failing that you could try switching IC20 and IC21 (they are
socketed) to see if the fault shifts to the PWM rate. I would not be
surprised if the fault is somewhere on the 367. Call in as you proceed...

Cheers,
Andy


On 21/12/2009 14:27, "f115@rocketmail.com" <f115@rocketmail.com> wrote:

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>  
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> In recent years I've noticed that my P6 takes quite a while to to warm up and
> get in tune. I read some older posts here and it sounds like 10 seconds is
> normal. Mine takes longer, maybe a minute, but it's more like a slow VCO LFO
> rather than individual notes being out of tune. My gut would tell me to start
> replacing capacitors but I haven't pursued it and I'm not sure how it would
> affect the sound by doing that.
> 
> Also - generally speaking the synth out of tune and is off by a semi-tone or
> so. I've got my tune knob all the way to the left and I imagine it'll get
> worse over time. Note for note the synth is ok so the calibration appears to
> be normal, but as I said, overall it's noticeably out of normal range.
> 
> Thanks everyone!
> (Hammering you guys with questions today) :)
> 
>  
>    
> 
> 



[Non-text portions of this message have been removed]

Thanks for all the suggestions! I'll let you know what I find. I'll be making time for this P6 and the other two over the holidays. Lots of troubleshooting to do :)

Well I'm happy to report that I made some progress.

Starting with my main Polysix:

I was able to test the power supply as you suggested. It checks out fine at all the test points: +/- 4.95 V and +/- 14.96 V.

I went through the KLM-367A and replaced it with a fresh battery. My battery mod was done about 15 years ago and it appears that the original mod never included the 1N914 and cap removal so I did that. I also re-checked the continuity for IC26, IC30, IC31, and IC32. Everything appeared to be working. Since I had the 367A out I gave it a thorough cleaning too and double checked the solder joints in key areas. I reflowed a few spots for good measure in kew areas on the card as well as on the MG board. All in all I didn't make major sweeping changes but I somehow managed to get rid of that intermittent MG level. Unfortunately I'm not certain how that was achieved. I did lose the original patch data though by keeping the battery out long enough. I also removed the 8048 and tried two others to test their integrity. Perhaps all this had some effect. It also doesn't seem to detune as heavily as before either so I just don't know what changed it so drastically! The clean up and tune was well worth it though. It feels like a fresher instrument. Time will tell. I'm watching and listening to it closely.