polysix repair

DETOX · Joined: May 22, 2008 Posts: 143 Location: Germany

i don't know wether i already posted this or anyone else did, the search function didn't result in any concrete matches.

i just got a polysix for free but as usual the battery was leaking and damaged the memoryboard. i already found an online tutorial on the repair and did all the steps of the board removal as described.

btw: before the removal the synth did still work more or less. the dco had some malfunctions as the attenuator and some other sections but it did work somehow.

now i'm at the point of the actual board restoration and battery replacement but i'm a little scared because i consider myself not as an overwhelming solderer ( i have basic skills so to say). the acid covers some traces and some legs of the ic being close to the battery (unfortunately i don't have a digicam atm so i can only describe it's condition).

my question is: what are the main mistakes i can make?
will it be doable for me as a relatively untrained technician?
will there be any problems before switching it on the first time after restoration?

thanks for your replies !

radek tymecki · Joined: Mar 22, 2009 Posts: 85 Location: PL

http://www.oldcrows.net/~oldcrow/synth/korg/polysix/crowlm367/klm367a_img.gif

get a multimeter and check all connections near ic30 and 31

ian-s · Posted: Mon Oct 05, 2009 2:14 pm Post subject: Re: polysix repair

Mooger5 · Posted: Mon Oct 05, 2009 4:51 pm Post subject: Re: polysix repair

Practice first, get some trashed PCB and wires, and practice. Make all sorts of crazy soldering until you´re confident enough.
After cleaning the PCB, do the continuity tests as advised. If you find the acid corroded some copper tracks you´ll either have to solder insulated thin solid-core copper wires on the damaged spots or link the components directly, lead to lead (or IC socket pins).

Good luck.

DETOX · Joined: May 22, 2008 Posts: 143 Location: Germany

wow !
believe it or not, i didn't finish the klm367 repair yet. i finally have got all parts together. the only part missing is the component called R17. i know it's a resistor array but because i live in germany i need to know the german word to tell the dealer what i'm actually looking for. can anybody 'translate' "resistor array" into german? i need the real name ! thank you.

btw: can i replace a resistor array by just soldering 8 10k resistors together?

DETOX · Joined: May 22, 2008 Posts: 143 Location: Germany

okay, i found it out myself again !!!

DETOX · Joined: May 22, 2008 Posts: 143 Location: Germany

i soldered everything together but the synth still doesn't work properly. the filter and envelope section seem to be okay, the arpeggiator also works as the effects section does.

the memory section doesn't really work......several leds lght up constantly but it seems not to work at all.

the vco section bothers me the most. i can't switch between pulse and saw. the only wave i can hear is a pulsewave, pwm works too. the sub oscillator seems not to work either. when i press down the memory board and hold it the subosc seems to work, but switching between octave 1, 2 and off doesn't work.

any solutions? i replaced the battery, the r17 resistor array, and the ic beneath. soldering is a bit messy but i think all traces should be connected properly.

did anybody of you order a cloned km367 board?

EdisonRex · Posted: Tue Nov 15, 2011 3:12 pm Post subject:

You might try checking the top board. When I powered on my Polysix after many years of dormancy, and after removing the battery (I had stored it in a way that left a nice corrosive spot on the back panel but didn't hideously damage the board), there were a number of issues, mostly with the front panel selections and the calibration (the voices were out of tune).

I haven't really started to restore the instrument, but capacitors go bad over time and I expect that has effects on the control. You might also have tin whiskers or other shorts which cleaning will help.

Mooger5 · Posted: Wed Nov 16, 2011 2:37 am Post subject:

philoop · Joined: Aug 19, 2011 Posts: 15 Location: hamburg

if many LEDs are on and sound misbehaving ts definitly the tracks on klm 367
to ic 30 31. I fixed three polys and it always was that problem....
thanks to oldcrow

DETOX · Joined: May 22, 2008 Posts: 143 Location: Germany

oh, great advices from you guys ! thanks for that. i'll definitely give it another try (or even some more). it's sitting in my studio half naked anyway.

if it worked again i'd be so happy ! i fell in love with the filter so badly.

philoop · Joined: Aug 19, 2011 Posts: 15 Location: hamburg

hurry up to extract the battery or its going to corrode its way to the pcb even further...long live the polysix

DETOX · Joined: May 22, 2008 Posts: 143 Location: Germany

YashN · Joined: Jun 27, 2011 Posts: 104 Location: Canada

Undergoing the same process here.

DETOX · Joined: May 22, 2008 Posts: 143 Location: Germany

DETOX · Joined: May 22, 2008 Posts: 143 Location: Germany

where do i get replacement boards?

djs · Joined: Jan 14, 2011 Posts: 4 Location: south beloit, il

replacement boards can be ordered here:

http://sites.google.com/site/jedjorgensen/

YashN · Joined: Jun 27, 2011 Posts: 104 Location: Canada

One circuit is very damaged: there are so many breaks around the battery area. It's one of the old boards where the chips were mostly soldered on.

The other circuit, which also had battery damage, surprisingly seems good, and it's the newer version, with most chips socketed.

One of the Quad gate chips is dead, so the socketed ones can be reused.

While cleaning the old circuit, I damaged the resistor array, so I need to order a new one.

In both synths, I have no control over the Cutoff and Resonance.

Arpeggiator in the newer one is working.

Some sounds in both synth: a wailing, rising tone sound.

Still a lot of work to be done: buying sockets for the un-socketed one, with the replacement Quad gate chips and the resistor array too.

Can't wait to hear them restored again. I think they're going to be fabulous synths, and I will also mod them too, as I've been doing with all my resurrected synths.

DETOX · Joined: May 22, 2008 Posts: 143 Location: Germany

JingleJoe · Posted: Sun Jan 22, 2012 11:54 am Post subject:

defog · Joined: Aug 24, 2011 Posts: 113 Location: Philadelphia

As far as repairing these and other old synths, in my experience it is always comes down to a single trace on the board or a single wire that does not appear to be physically damaged/cracked that is the culprit. A lot of times the ICs and everything else will work perfectly fine once they're found (except in the case of IC 31 on the Polysix).

I worked on one of these a few years ago that I pretty much had to rebuilt the entire bottom left corner of the PCB's traces with bus wire to get it going again. Took a little while and a very steady hand and exacto blade to make sure it was clean and no micro-bridges were made, but it worked perfectly afterward.

DETOX · Joined: May 22, 2008 Posts: 143 Location: Germany

defog · Joined: Aug 24, 2011 Posts: 113 Location: Philadelphia

I just automatically lay down bus wire on cracked/scratched traces now when I do repairs to keep it from cracking again. I just make sure to follow the exhisting trace's shape to avoid any sort of RF craziness.

YashN · Joined: Jun 27, 2011 Posts: 104 Location: Canada

YashN · Joined: Jun 27, 2011 Posts: 104 Location: Canada