Archive of the former Yahoo!Groups mailing list: Discussion about the Korg PolySix synthesizer

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Subject: Re: [PolySix] I have my dream synth - help me get it working!

From: Bob Grieb <bobgrieb@yahoo.com>
Date: 2014-02-20

Hi,

    Others know the Polysix better than I, but here are some suggestions anyway:

  The first thing to do is download the service manual from the web and start getting
familiar with the circuit, and where the different test points are.

  Then I would measure the power supply voltages and make sure they are good.
Voltages that are too high can damage expensive chips.

   Assuming the voltages are good, I would look at the control signals that feed the voice
chips.   The gate signal turns on the LED, so it seems that one is working for all
six voices.  But there are other voltages that are separate for each voice.   Maybe they
are only getting to voice 0?   If you put the synth in unison mode, then I would expect
the control voltages for the VCA and the filter cutoff and pitch to be the same for all
voices.  If you turn up the sustain and put something on a key to hold it down,  then you can
measure the voltages and see if they are getting to all 6 voices.  You should be able to measure
some of the voltages with just a DMM as they won't be changing for a sustained note.

   Unless you have a power supply voltage that's too high, I wouldn't expect 3 of the voices
to fail in a few weeks.  Hopefully it's just one thing that has failed and is keeping them
from coming on.

    Hope that helps.

        Bob


From: "moondog1311@gmail.com" <moondog1311@gmail.com>
To: PolySix@yahoogroups.com
Sent: Wednesday, February 19, 2014 3:31 PM
Subject: [PolySix] I have my dream synth - help me get it working!

 
Hello good Polysix people,

After nearly 30 years of lusting after a P6, I finally took the plunge and bought a lucky dip from eBay. Good overall cosmetic condition, inside it had the usual battery corrosion issues; but the board has been mended (rather crudely) with a new lithium battery, and the CPU seems to be behaving and presets are remembered and recalled.

The keys were appalling, only a few worked. So I stripped 'er down and rubbed 'er good and proper with alcohol (no giggling please) and I now have a working keybed.

Which brings be to the issue at hand, only the 1st voice seems to be working. On poly mode you'll have to hit a key six times before it fires again. on Unison, it acts as a mono synth. Now the strange thing is when this was purchased last week at least 4 of the voices were working (it was hard to tell because of the unresponsive  keys and a irate seller).

All the internal LEDs fire in order when a key is pressed. I am really hoping that it's not the filter or envelope chips that have all gone. If so, how and why so quickly?

Anyone have any ideas?

I know it only has one voice, but it is truly sublime. I just need five more..

Respectfully,

Moondog