Korg Poly800/EX800 Users

I performed the slayer mod about two years ago and was very pleased 
with the results, but now I want to see if I can get more knobs on 
the korg. I remember when I put the pots in the two parts of the 
board were labelled VR2 & VR5, and there were several other "VR" pots 
around the circuit board. I assume these correspond with other filter 
effects, and was wondering if anyone could tell me which ones would 
allow me to put knob control on the EG, rate, DCO, VCF and delay 
functions of the original poly800. I honestly can't make heads or 
tails out of the zipped schematic of the korg.
Also, if I were to put knobs on these functions, would I have to 
ground the upgrade and have a resistor again (finding the resistor 
was the hardest part of the slayer mod for me!)
any info would be great, thanks
~AJB

From memory this question was answered on this list in the history.
When i first joined the list the first task was to go back through the  
list and see what existing knowledge was in it, before asking questions  
that had already been answered. this took me the best part of two days  
part time hehe

The answer you seek IS in the archive, tho i don't recall exactly where.

unfortunately these other pots don't provide useable additional  
features, i think one controls the white noise generator i forget what  
the other two are for.

Best regards,

Marcus Wilson

On Sunday, April 25, 2004, at 04:30 PM, a7634@... wrote:

> I performed the slayer mod about two years ago and was very pleased
> with the results, but now I want to see if I can get more knobs on
> the korg. I remember when I put the pots in the two parts of the
> board were labelled VR2 & VR5, and there were several other "VR" pots
> around the circuit board. I assume these correspond with other filter
> effects, and was wondering if anyone could tell me which ones would
> allow me to put knob control on the EG, rate, DCO, VCF and delay
> functions of the original poly800. I honestly can't make heads or
> tails out of the zipped schematic of the korg.
> Also, if I were to put knobs on these functions, would I have to
> ground the upgrade and have a resistor again (finding the resistor
> was the hardest part of the slayer mod for me!)
> any info would be great, thanks
> ~AJB
>
>
>
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AJB
 
Yes, its true there is only very Limited variables that we can tweak, in these
machines...... especially since the majority of features are implemented
in FIRM_ware..... i.e. Read-Only ROM. The Computer within does a remarkable
job of digitally synthesizing these effects .... we have only the Play parameters
to change, by design. The POTs, or variable resistors on the Mother_Board,
should not be messed with, other than the two you have already,,...and that
can result in rather extreme results ! 
VR1 is to adjust the 5 Volt Regulator,
so that is a definite No-no ( unless to minor adj. 5v to 5.000V)
VR3 sets the Max-Noise level , as Function 33 's ceiling value
VR4 is the Digital-to-Analog Offset adjustment and by no means should change
from its optimum setting , as VR1.
 
The two pots you have played with can have some refinements as yet...
VR2 is VCF_Cutoff frequency adjustment.....the factory adjustment procedure
just has you tweak until a certain amplitude is maximized.... +/- that peak 
means you can only reduce the degree of the effect off optimum.
VR5 is limiting the maximum amplitude so as to not overdrive the NJM2069 VCF
chip into oscillation, but then that effect is desirable if not at its extreme value.
 
Anyway, refer to two experts in the archives : "plutoniq9" and marjan urekar
Cheers
Dan

thanks for the info on the other VR pots, I guess I shouldn't mess 
with them or i will kill my korg... I assume this means that I could 
only really add a white noise pot (which I really am not too 
interested in). 

I'm just wondering if there are any other tweaks I could make the it 
that aren't too-difficult for someone who's a little shaky with the 
soldering iron... I was particularly hoping to be able to adjust the 
filter rate and EG intervals with analog controls, is that at all 
possible or am I having a pipe dream? 

~AJB
PS - Even if that is a no-go, does anyone know of any other not-too-
strenuous mods that can be applied to the poly800?



--- In korgpolyex@yahoogroups.com, Dan Brewton <dannobe123@y...> 
wrote:
> AJB
>  
> Yes, its true there is only very Limited variables that we can 
tweak, in these
> machines...... especially since the majority of features are 
implemented
> in FIRM_ware..... i.e. Read-Only ROM. The Computer within does a 
remarkable
> job of digitally synthesizing these effects .... we have only the 
Play parameters
> to change, by design. The POTs, or variable resistors on the 
Mother_Board,
> should not be messed with, other than the two you have 
already,,...and that
> can result in rather extreme results ! 
> VR1 is to adjust the 5 Volt Regulator,
> so that is a definite No-no ( unless to minor adj. 5v to 5.000V)
> VR3 sets the Max-Noise level , as Function 33 's ceiling value
> VR4 is the Digital-to-Analog Offset adjustment and by no means 
should change
> from its optimum setting , as VR1.
>  
> The two pots you have played with can have some refinements as 
yet...
> VR2 is VCF_Cutoff frequency adjustment.....the factory adjustment 
procedure
> just has you tweak until a certain amplitude is maximized.... +/- 
that peak 
> means you can only reduce the degree of the effect off optimum.
> VR5 is limiting the maximum amplitude so as to not overdrive the 
NJM2069 VCF
> chip into oscillation, but then that effect is desirable if not at 
its extreme value.
>  
> Anyway, refer to two experts in the archives : "plutoniq9" and 
marjan urekar
> Cheers
> Dan

Mon April 26

Ha ! Yeah, Truly a pipe dream unless you care to revearse Engineer the entire

EPROM.... the code resident there , controls those parameters..... I actually have

hex dumps and a Dis-Assembler listing of the stock Poly800-1, ....IF you are a

Machine-Language Programmer and speak the native tongue of Intel 8085, then

by all means......!!!! :)

I myself have been intrigued by doing the same, as I have quite a bit of experience

programming the 8085, etc.....( Computer Science Degree, etc...) and I have a 

ROM burner and have been doing Electrical Engineering Tech work all my

Adult life.....So, anyway it takes ooodles of TIME, which, as you get older, is

ever diminishing .....such is life, but SOMEday, I keep telling myself , some-damn-day !!! :)

Dan