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Thread

Korg PolySix - Repair issues - Please help

2013-12-29 by <mrjdevries@yahoo.com.au>

Hi all.

I recenty got a PolySix that has issues..

Initially it would not power up / crash.

A few corroded traces on the Control Surface (directly above the battery) and a dead opamp caused most of this.

Surprisingly, even though the battery had corroded, the CPU board (367) was rather intact.

It now plays mostly fine except for one or two issues.

The preset buttons 1-4 do not work, as does the Attenuation rotary switch.

Pressing button 5 switches preset, but curiously switches on the LED's on buttons 4&5.

There are a few weird issues with incorrect LED's being lit up (Tape etc) when certain presets are selected.

The good news is I have a working 367 board, and swapping that over results in a perfect PolySix with none of the above issues.. So I can assume the fault is on the 367 board

I've replaced IC 31 & IC 30 (74LS08)

I've replaced IC's 26 & 24 (4042) - IC 24 is mislabled on my schematic as IC34

I've replaced IC's 29 & 35 (4042)

I've swapped over the CPU IC (uPD8048C)

I've thoroughly buzzed out for corroded traces in the digital lines, but can't seem to find any that are open circuit.

As the push buttons 1-4 are not responsive with the bad CPU board, I can only assume that the issue relates to DO4 - would this be correct?

The Attenuation also uses DO3 as well as P11,P12,P13

Does anyone have any pointers on what to check?

Could Faulty RAM be responsible for this kind of fault? I am suspecting not as I'm unable to change to some patches and faulty ram (probably) would not stop that from happening.

Any pointers / assistance will be greatly appreciated..

Regards.

Mike

Australia.

RE: Korg PolySix - Repair issues - Please help

2013-12-29 by <rufushaw@yahoo.it>

hello,

assuming that everything is fine on buttons board, each time i had troubles with assigner i found issues or broken traces between 8048 outputs and CN10.

Re: [PolySix] Korg PolySix - Repair issues - Please help

2013-12-29 by Dennis Matana

Hi Mike,

Make sure that all the data lines are continues through out the board. So check pin for pin if D0 to D7 are present on their respective data line. Also check if the datalines have contact with the resistor array situated between the cpu and ic30/31.

BR, Dennis

http://soundcloud.com/wifi

www.facebook.com/matanateknik

On Sunday, December 29, 2013 2:51 AM, "mrjdevries@yahoo.com.au" <mrjdevries@yahoo.com.au> wrote:

Hi all.

I recenty got a PolySix that has issues..

Initially it would not power up / crash.

A few corroded traces on the Control Surface (directly above the battery) and a dead opamp caused most of this.

Surprisingly, even though the battery had corroded, the CPU board (367) was rather intact.

It now plays mostly fine except for one or two issues.

The preset buttons 1-4 do not work, as does the Attenuation rotary switch.

Pressing button 5 switches preset, but curiously switches on the LED's on buttons 4&5.

There are a few weird issues with incorrect LED's being lit up (Tape etc) when certain presets are selected.

The good news is I have a working 367 board, and swapping that over results in a perfect PolySix with none of the above issues.. So I can assume the fault is on the 367 board

I've replaced IC 31 & IC 30 (74LS08)

I've replaced IC's 26 & 24 (4042) - IC 24 is mislabled on my schematic as IC34

I've replaced IC's 29 & 35 (4042)

I've swapped over the CPU IC (uPD8048C)

I've thoroughly buzzed out for corroded traces in the digital lines, but can't seem to find any that are open circuit.

As the push buttons 1-4 are not responsive with the bad CPU board, I can only assume that the issue relates to DO4 - would this be correct?

The Attenuation also uses DO3 as well as P11,P12,P13

Does anyone have any pointers on what to check?

Could Faulty RAM be responsible for this kind of fault? I am suspecting not as I'm unable to change to some patches and faulty ram (probably) would not stop that from happening.

Any pointers / assistance will be greatly appreciated..

Regards.

Mike

Australia.

RE: Korg PolySix - Repair issues - Please help

2013-12-29 by <josh.nursing@gmail.com>

Mike,

I think it's crucial that you go through the calibration procedure in the Service Manual: if your components and boards are fine but the Polysix is misbehaving because it's uncalibrated, no amount of tinkering will help.

So, I'd first try these, then that will help with diagnosis.

Good luck!

Yash

Re: [PolySix] RE: Korg PolySix - Repair issues - Please help

2013-12-30 by Mike

The issue is that the main CPU board does have a fault. I'm trying to diagnose where this fault is.

It's not a calibration issue.

I suspect that one of the data lines is being pulled high or low. I've got my scope back from a friend, so this will help diagnosing what is at fault.

I'll report back with any updates.

Kind regards.

Sent from my phone while driving.

On 30 Dec 2013, at 9:41 am, <josh.nursing@gmail.com> wrote:

Mike,

I think it's crucial that you go through the calibration procedure in the Service Manual: if your components and boards are fine but the Polysix is misbehaving because it's uncalibrated, no amount of tinkering will help.

So, I'd first try these, then that will help with diagnosis.

Good luck!

Yash