Discussion about the Korg PolySix synthesizer

I haven't seen any more posts on this thread since I mentioned getting some
test equipment. I didn't mean to spoil your fun. It just sounded like you
were getting to the point where it would be cheaper and less time consuming
to start with a brand new bare board from Jed or Scott and start putting new
parts on it than to try and remove all those old parts from the existing
KLM-367 board.

This isn't like an automobile where basic maintenance is needed to prevent
catastrophic failure of some other parts, like changing the oil to prevent
engine damage. The only part of the Polysix where that might apply would be
the large electrolytic caps in the power supply. I've never needed to
replace any of the smaller electrolytics. Some other synth sites like to
propagate "the great Mylar scare", since old Mylar caps have been shown to
cause problems on some other synths. I haven't seen this problem in any
Polysix that has passed through my hands, but maybe somebody else on the
board has.

As Scott says on his Old Crow site, and I think Andy has mentioned it as
well, some old 4000 series chips seem to have a definite life span. I have
replaced some chips on various Polysixs over the years. Interestingly
enough, they were all 14051 chips that had either failed completely or had
gotten slow and sloppy. Maybe Korg just got a bad batch. I've never heard of
problems with the ceramic caps or resistors, unless they were damaged by a
battery leak.

In any case, it's your machine so have fun with it. If you like a hot
soldering iron in your hand, then go for it, but any improvement in sound
might be just wishful thinking if you are operating blindly without the
right tools to see what really needs to be fixed.

 

Don Backshall

 

  _____  

From: PolySix@yahoogroups.com [mailto:PolySix@yahoogroups.com] On Behalf Of
backshall1
Sent: Tuesday, June 05, 2012 5:32 PM
To: PolySix@yahoogroups.com
Subject: RE: [PolySix] Polysix service checklist for the amateur ;)

 

  

It sounds like you are already well on your way to "what really, really
doesn't need fixing". Spend some money on test equipment like an old
oscilloscope and a capacitance meter first.

Don Backshall

_____ 

From: PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>
[mailto:PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com> ] On
Behalf Of
analoglove
Sent: Tuesday, June 05, 2012 4:40 PM
To: PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com> 
Subject: [PolySix] Polysix service checklist for the amateur ;)

I'm planning on doing some basic maintenance on my old Polysix. I've been
reading threads and manuals found here on this group, excellent tips,
thanks!

I thought I'd like to make a 'basics' checklist, not about solving specific
problems but just best practice for the owner who wants to take care of the
synth, and keep it sounding fresh and strong.

1) Electrolytic capacitors: My synth is sounding quite dusty and a bit dull
at this point, so I'll put in new electrolytic capacitors, a reasonable
thing to do after 30 years. I'm going with mainly Vishay 517Ds available at
Mouser.

2) I'm putting in all new 4000-series ICs, as recommended here (Old Crow):
http://www.oldcrows.net/~oldcrow/synth/tips.txt
I'm getting TI's series with the CD4xxxBE or CD4xxxBEE4 part numbers. 

Is there anything else that you would do without hesitation? I mean, I know
that there may be some tuning work involved also, but I'm thinking about
whether there's more hardware that should be replaced?

Would you take the time to swap all the old resistors, or at least those
made of carbon?
Would you bother to swap the mylar and ceramic caps, or are you thinking
that they will keep on trucking for years to come?

Hope to hear your inputs before I start operating, and I'm hoping not to fix
what really, really doesn't need fixing ;)

Thanks,
Analoglove

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