Discussion about the Korg PolySix synthesizer

Hi All,

First Post in this wonderful Group, so.....

I have acquired a P6 with the clone KLM board, reverse of the board shows that all the necessary Bug Fixes have been seen to with Jumpers/Bridges.

The issue is that the MG Mode Switch does the following:

VCO - the VCF modulates by LFO (no VCO)

VCF - the VCF modulates by LFO (slightly different to above)

VCA - the VCF modulates by LFO (slightly different to previous ones above)

LFO Delay is working but also has a short delay of a second even at Zero.

All these MG Mods happen even with Level at Zero, though they do intensify as the Level is turned up.

Any help, knowledge, advice would be appreciated

Jim

>
> Hi All,
>
>
> First Post in this wonderful Group, so.....
>
>
> I have acquired a P6 with the clone KLM board, reverse of the board
> shows that all the necessary Bug Fixes have been seen to with
> Jumpers/Bridges.
>
>
> The issue is that the MG Mode Switch does the following:
>
>
> VCO - the VCF modulates by LFO (no VCO)
>
>
> VCF - the VCF modulates by LFO (slightly different to above)
>
>
> VCA - the VCF modulates by LFO (slightly different to previous ones above)
>
>
> LFO Delay is working but also has a short delay of a second even at Zero.
>

> I just checked the board makers website and their parts list matches mine.

>
> Am 01.03.2018 um 10:35 schrieb jimpster@me.com [PolySix]:
> > I just checked the board makers website and their parts list matches
> mine.
> Can you send an URL to the makers wegsite?
>

>
> I see, well I'm working with the clone board so best to reference
> that. I assume you do not have the clone in your P6?p
>

> have another fully working P6 so I swapped over the KLM 367 board from
> that one into the faulty P6.

> So, I'm still none the wiser with the clone board. Filter is always
> modulating no matter where I set the MG switch.

>
> Hi Don, thanks for your continued advice. I have swapped around all
> the the identical IC's to different sockets to eliminate a bad chip
> but the sound is consistent irrelevant of the location.
>

>
> Hi Florian,
>
>
> Yes, 1.6v and 1.8v constant on those socket pins with chip removed

On 01.03.18 19:12 , jimpster@me.com [PolySix] wrote:

 

0.2v on pin 1

This sound reasonable. So I'd replace the LM339.

Florian

On 01.03.18 21:01 , synthguy80@gmail.com [PolySix] wrote:

> Mine behaves differently from above in that I get some VCO modulation regardless
> of the switch position.
Keep in mind that there is VCO modulation also via the Modwheel. Disconnect CN09 which connects the bender section with the left panelboard. Only then you are sure, that it is not(!) the Modwheel.

Florian

Hello everyone,

Regarding to this subject, thank you all for contributing, i'm also still dealing with a restored polysix having MG issues wich i will describe here later, after i have checked all the common bugs with jed's replacement pcb connectors cables mod wheel and ic's. For now i just have a question regarding that strange transistor with four pins. What possible replacement option is available for this (i assume) nowadays obsolete part ?

Thanks in advance.

On 2018-03-01 19:15, jimpster@me.com [PolySix] wrote:

Thank you Nekoma, not bad English at all. Yes the cable socket connectors on the board do look like they were transplanted, it is something to consider.

 

On 2018-03-02 13:05, backshall1@bellsouth.net [PolySix] wrote:

> It looks like you attempted to attach a .gif image but it was blocked.
> I assume you are talking about the 5-pin 2SA798. This is a dual
> transistor which the big parts stores don't have in stock anymore but
> there are a few smaller places that have them, at bigger prices. You
> can usually find them on Ebay. I don't know of any other part that is a
> direct replacement.
> Don B.
>
> FROM: 9-0-9 ninonine@xs4all.nl [PolySix]
> SENT: Friday, March 2, 2018 4:54 AM
> TO: PolySix@yahoogroups.com
> SUBJECT: Re: [PolySix] Re: P6 MG Oddity [1 Attachment]
>
> Hello everyone,
>
> Regarding to this subject, thank you all for contributing, i'm also
> still dealing with a restored polysix having MG issues wich i will
> describe here later, after i have checked all the common bugs with
> jed's replacement pcb connectors cables mod wheel and ic's. For now i
> just have a question regarding that strange transistor with four pins.
> What possible replacement option is available for this (i assume)
> nowadays obsolete part ?
>
> Thanks in advance.
>
> ---
> Greetings,
>
> 9-0-9
>
> On 2018-03-01 19:15, jimpster@me.com [PolySix] wrote:
>
>> Thank you Nekoma, not bad English at all. Yes the cable socket
>> connectors on the board do look like they were transplanted, it is
>> something to consider.
>
>

On 2018-03-02 17:16, axmonti@yahoo.ca [PolySix] wrote:

> Hi 9-0-9,
>
> I've made plenty of replacements for the 2SA798 - just use two matched
> PNP transistors and place them back-to-back with their emitter tied
> together.
>
> Here are the transistors I use (I order at least 10 to end up with a
> matching pair).
>
> Here's the circuit you need to build (the PNP one) to match
> transistors. I recommend ordering two 0.1% resistors for your tester to
> avoid having to add a pot to make up the slight difference in
> resistance between the pair. You also have to have a +/- power supply
> (12-18V is fine) setup.
>
> The 2SA798 pinout is BCECB, so it's easy to tie the emitters together.
> Some people epoxy or zip-tie the transistors together, but they are
> pretty much exposed to the same temperature within an enclosed case, so
> I haven't found a need to perform that extra step.
>
> You can also use the same procedure to build 2SC1583 replacements; just
> use an NPN transistor such as this one (and flip the diode and power
> supply in the transistor matching circuit).
>
> Hope this helps!
> - Andrew
>
>
>
> -------------------------
> Posted by: axmonti@yahoo.ca
> -------------------------