Korg Poly800/EX800 Users

Hi Andrew,

Best to start looking at the chorus control signal that goes from the main board to the chorus board. Use a multimeter to check that the signal goes up and down when you turn chorus on and off. You will need to download the schematics from the files section.

/Mike
 

    On Sunday, October 7, 2018, 2:32:55 AM EDT, Andrew Morrison amorrison651@... [korgpolyex] <korgpolyex@yahoogroups.com> wrote:  
 
     

Hey All,Recently picked up a very grubby but very functional unmodified korg poly 800 mk1. Love the sound of the filter :O Everything seems to work (all the keys/midi/buttons/other parameters) as it should, except for the chorus which will just not turn on. I've tried it in stereo, mono and headphones separately.
I've had a look under the hood and whilst it was quite dusty, I've cleaned that all out and can see no signs of battery acid leakage/damage and comparing to other online photos I can see no cosmetic damage. The top and underside of the chorus board looks perfectly intact and undamaged to my eyes.

I've reset to factory settings and got fresh batteries in there but no luck getting that chorus to turn on. Anyone have any ideas on whether I'm missing something simple here, happy to provide some up close picks of the internals if anyone has any ideas?

So check the power rails to the chorus board. There are three: +5, -5
and +9 volts.
Then check the chorus signal line. Which I think you're saying you
checked that. But I can quite tell from your message below if that is
what you actually tested.
You can also test the noise gate signal line too. Press a key and the
noise gate to should turn on, and wait until the EG's all finish, and
it turn off. Helpful to know if you're testing is actually working.
/MikeOn Thu, 2018-10-11 at 13:25 +0000, amorrison651@... [korgpolyex]
wrote:

> Hi Mike
> 
> 
> Thanks a lot for the reply. So I've checked with my multimeter and
> can't see any differences between on/off (1/0) settings on parameter
> 48. So I suppose this a power issue to the chorus board
> 
> Best Wishes,
> Andrew
> 
> 
> ---In korgpolyex@yahoogroups.com,  wrote :
> 
> Hi Andrew,
> 
> Best to start looking at the chorus control signal that goes from the
> main board to the chorus board. Use a multimeter to check that the
> signal goes up and down when you turn chorus on and off. You will
> need to download the schematics from the files section.
> 
> /Mike
> 
> 
> On Sunday, October 7, 2018, 2:32:55 AM EDT, Andrew Morrison
> amorrison651@... [korgpolyex] <korgpolyex@yahoogroups.com> wrote:
> 
> 
>  
> Hey All,
> Recently picked up a very grubby but very functional unmodified korg
> poly 800 mk1. Love the sound of the filter :O Everything seems to
> work (all the keys/midi/buttons/other parameters) as it should,
> except for the chorus which will just not turn on. I've tried it in
> stereo, mono and headphones separately.
> I've had a look under the hood and whilst it was quite dusty, I've
> cleaned that all out and can see no signs of battery acid
> leakage/damage and comparing to other online photos I can see no
> cosmetic damage. The top and underside of the chorus board looks
> perfectly intact and undamaged to my eyes.
> I've reset to factory settings and got fresh batteries in there but
> no luck getting that chorus to turn on. Anyone have any ideas on
> whether I'm missing something simple here, happy to provide some up
> close picks of the internals if anyone has any ideas?
>