Discussion about the Korg PolySix synthesizer

A while ago I was given - to clean and repair - a pair of Polysixes that belonged to a 
friend. I managed to get the keyboards cleaned and working perfectly, one has a green 
battery, the other has a blue one, and one of them (it varies which one as I keep moving 
the chip) has a faulty 2056 chip.

Originally both had bad keyboards, one had a stuck voice, and that was the size of it. I 
repaired both keyboards, identified the faulty voice, and brought the cleaner of the two 
down to the studio to play with. It developed a new fault:

When powered up, half the LEDs on the patchbank light up, not all of them.
Selecting patches is unpredictable within a fixed pattern - 2 can be selected, but doesn't 
light the LED.
Tape Enable doesn't work. The LFO cranks up, but nothing else happens.
Switching the Sub Oscillator doesn't work correctly.

I swapped the 371 etc. boards over in the hope that it might be that, and of course, put 
the working filter chip in the other keyboard. I think the fault must lie within the 367A 
board, but the battery (blue) doesn't appear to have leaked.

The other one appears to be working normally, but I'm holding off putting the screws in 
until I can confirm a couple of things:

First - the green battery. From what I've read these don't suffer the same leaking and 
some places imply green ones are NiMH. Is that the case?
Second - when first started, the Polysix 'rises' in pitch until it is in tune. It's just the first 
note/s player - basically it stabilises. I haven't read of this behaviour anywhere so I'm 
assuming something is failing.

Patch storage works, and I have loaded/saved to tape with it. Since all the keys work and 
this works, once I can find out if the pitch rise behaviour is normal/fixable, and the battery 
can be trusted, I can put the synth back together and return it.

But the first keyboard; it was working fine then developed this issue without any visible 
signs - all socketed chips are seated (I have removed and cleaned connections with no 
noticeable changes), the voice chips all work aside from the broken one, and the button 
board works in the other synth just fine (and the one in the other synth, which works, was 
originally in this one).

I expect a course of replacing electrolytics might help the working one a bit, but the 
broken one sounds more complex.

Best Wishes,
Richard

Richard Kilpatrick wrote:
> I swapped the 371 etc. boards over in the hope that it might be that, and of course, put 
> the working filter chip in the other keyboard. I think the fault must lie within the 367A 
> board, but the battery (blue) doesn't appear to have leaked.

But is it still working?

My Trident MK2 refused to work without a proper battery.

   Niels

On 14 Jul 2006, at 14:52, Niels Ott wrote:

> Richard Kilpatrick wrote:
>> I swapped the 371 etc. boards over in the hope that it might be  
>> that, and of course, put
>> the working filter chip in the other keyboard. I think the fault  
>> must lie within the 367A
>> board, but the battery (blue) doesn't appear to have leaked.
>
> But is it still working?
>
> My Trident MK2 refused to work without a proper battery.

I'm getting a reading of 3.6V on the blue battery, 3.99 on the one  
with green battery (which I now can't remember if I posted before or  
after, but what I did today was swap the assigner/voice board over  
and put the 8302 dated SSM2056 I'd nicked from blue battery back onto  
the board it came from - so they're all matched). So now blue battery  
has a board with older SSM chips (well, one is a newer one), a patch  
assigner board I am pretty sure is failing in some way (now the 366B?  
boards have been swapped too and worked the same in either), and  
green battery is working pretty much as I'd expect beyond the tuning  
'warming up'.

I've now swapped parts over so often including feet that I've  
forgotten which was the better keyboard in the first place! But green  
battery is currently getting to hang out in the studio, hooked up to  
the Sequential Drumtraks' metronome output (the drums seem too weak  
to trigger the arp and the clock output is just nuts). I think I'm  
going to have to decide one is for spares; good keyboard, below  
average case, slight bend in the 371 board, all pots working well,  
both have had the wheels stripped, cleaned and rebuilt and keyboards  
too, but blue battery needs a battery, a voice chip and ???? repairs  
to the patch assigner at best. Oh, and feet. I don't know why only  
one had feet.

Richard

-- 
Tasty Other - Because Far Too Much in Life Makes Sense
Music for download - coming soon (RIP MP3.com)
G.A.S. http://www.dmc12.demon.co.uk/music/
Platform: PowerMac G5 2.0GHz Dual, 20" LCD, Logic, Hammerfall.

Richard Kilpatrick wrote:
>>My Trident MK2 refused to work without a proper battery.
> 
> 
> I'm getting a reading of 3.6V on the blue battery, 3.99 on the one  
> with green battery (which I now can't remember if I posted before or  

A few minutes after I had sent my reply, I switched on my Trident and
found it out of order. Obviously, the CPU board is in trouble, it
"displays values" on the patch selection LEDs which are impossible.
(Like patch 4 and 5 active at the same time.)

The battery is still in perfect condition.

So this falsified my assumption.

Right now, it came up working perfectly. I hate those kind of errors.

Furhermore it makes a little bit of low rumble on the output every once
a while.

Maybe I should check the output of the power supply.


> to trigger the arp and the clock output is just nuts). I think I'm  
> going to have to decide one is for spares; good keyboard, below  
> average case, slight bend in the 371 board, all pots working well,  
> both have had the wheels stripped, cleaned and rebuilt and keyboards  
> too, but blue battery needs a battery, a voice chip and ???? repairs  
> to the patch assigner at best. Oh, and feet. I don't know why only  
> one had feet.


Hehe. Sounds like a plan, to have one spare device. I wouldn't complain
about having another Trident.

   Niels