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Thread

Help.... with 12db/24db filter switch mod...

2003-12-15 by Blaine

I followed the directions below that are from a post a few months
ago and it's not working for me...I am not an electrician...i just
follow directions well and I did exactly what they say..so i don't
really understand why it is not working....is there a step missing
from the instuctions that i have attached? does anything get
soldered to the negative - pinpoint of c103 on the main board? well
here are the intructions i followed...hope someone can help.....oh
also I used an SPDT switch not a pot....
thank you in advance

This is how I implemented the mod on my Poly. I hope this helps...

The filter chip is marked "Korg njm2069". In my Poly it's mounted in
a socket,
making it very easy to notice. Solder wire leads to pins 5 and 6
(these are
the filter outputs.)

Connect these wires to the opposite terminals of a SPDT switch. Cut
C103 from
the poly mainboard and solder it's negative terminal to the common
point of
the switch, then solder a wire from it's positive terminal to it's
positive
pin position on the board.

Make sure it works, then find a way to mount your switch in the case.
An interesting expirement is to mount a 100k pot in place of the
switch,
one can get some really nice soft pads near the middle, gets really
quiet
though.

Re: [korgpolyex] Help.... with 12db/24db filter switch mod...

2003-12-16 by Dan Brewton

Well......there are several things that can go wrong with this kind of mod......soldering

directly to a Chips legs is dangerous to the chip, as overheating is easy to do....the

instructions should have reminded people of this possibility.....soldering to the backside

of the Printed Circuit board always makes more sense, however it is painful to remove the

entire PCB......well, taking the easy way out never works for me, anyway......also

C103......one must know which side of the capacitor is already wired to pin 6 (this

would have been a better place to gain access to pin6 without traumatizing the chip..!)

and so its opposite end is where the center-leg of the Switch must go to, after first

passing through C103 AND if somehow the cap was brutilized upon its removal,

then substitution could result in yet another failure mode....not obtaining another

"Non-Polarized" Cap or if poloraized ( as most electrolytics are !) then its being backwards would be another problem.....the instructions probably got that backwards......so give all that a try !

Cheers,

Dan

(FYI: I've more that 30 years in the Electronics Industry )

Re: Help.... with 12db/24db filter switch mod...

2006-09-21 by xelectric123

Hello.

I'm new to the list, so maybe few words about myself for a start. I'm
23 from Warsaw, Poland. I'm studying Electronics here at the Military
University of Technology in Warsaw, and sound synthesis is my hobby.
I've been using Poly-800 for 6 years now, and some time ago I found
this switched filter slope mod that I wanted to apply to my unit.

The problem is, that I've tried both using a standard switch and a
100k pot, and after each, there's no sound at the output. The filter
chip is ok, and C103 was soldered as instruction stated, because when
I desoldered switch/pot from 5&6 pin of the chip, everything went back
to normal. Maybe someone here had same problem and/or maybe know what
could possibly went wrong ?

X-Electric.