Korg Polysix gone mad

[flintan]

I have a Korg Polysix fitted with Kiwisix upgrades that all of a sudden has started to behave really bad. It has been working flawless since the upgrade a couple of years ago.

With output volume at zero there's a faint hum, with increased volume there's a lot of hum and buzz (amplified by the volume increasement). The filter seems to function properly but does not affect the buzz. The oscillator and the programs does not make any sense at all, there's just weird noise and crackles.

I would suspect a somehow faulty PSU but it outputs all voltages regulated within tolerance (+5, -5, +15, -15). I don't have a scope at home but could probably borrow one tomorrow.

Any ideas where to start?

 

[dmp]

How old is it? It might need a cap job (the electrolytic caps replaced). 
For old gear, the likely suspects are old bad caps, switches, pots.

Disclaimer I have no idea what the 'kiwisix' upgrades are

 

[beatnik]

Is the programmer still working ?

Do you still have a working KLM-367 board ?

Might be useful to place the old board in and see if that works.

Definitely do some fault finding with oscilloscope, it might be just a simple problem in the output stage

 

[Jarno]

Leaky battery? There are quite horrific cases to be found on the Internet, where mainboard and IC's are destroyed by this leaky backup battery. Repair it posthaste or there will be dire consequences!

 

[flintan]

Oh thanks for your replies!!

Haven't had time to deal any more with this the last days.

The Kiwisix upgrade is basically a replacement with some new functions (MIDI) and patches for the 367 program board as well as a fix for the leaky battery corroding the old board problem. So no leaky batteries here and also no old working KLM-367 board because that was all eaten by the battery. The PSU is also replaced with a new Kiwisix PSU

Guess I'll need to find and study a schematic and get myself a scope.

 

[saint gillis]

See if the pins of the processor are dirty. It's the big IC on a blue socket near the battery.  Remove it carefully, see if some pins are dirty or corroded, if it's the case scrub them gently with some thin sandpaper, and clean them and the socket with isopropyl alcohol, and put again the IC in its place, see what happens.

 

[5v333]

if you live in GBG or the westcoast and you wanna have somebody repair it for a reasonable cost,
give me call.

i just woke a polysix from the dead that had severe battery leakage issues.

 

[flintan]

See if the pins of the processor are dirty. It's the big IC on a blue socket near the battery.  Remove it carefully, see if some pins are dirty or corroded, if it's the case scrub them gently with some thin sandpaper, and clean them and the socket with isopropyl alcohol, and put again the IC in its place, see what happens.

Thanks, the entired program board is replaced with a new kiwisix board so there is no battery or corroded processor sockets. But perhaps the kiwisix board has gone bad somehow.

 

[flintan]

if you live in GBG or the westcoast and you wanna have somebody repair it for a reasonable cost,
give me call.

i just woke a polysix from the dead that had severe battery leakage issues.

Thanks, unforunately I’m in Stockholm.