weird problem on 1-8 voices board

[mg73]

One of the audio board(1-8) has a strange problem.
It sounds like it start to random panning on the decay of every voice on that board
when i use for example a Stereo Grand Piano
I suspect it has to do something with the CV controlling on the board and not none of the specific voices IC.
I´ve changed all of the SSM2300 and IC 7 but still no change
and of course also swapped the boards around.

Any idea of which soldered IC to look at,or anything else?

[mg73]

It seems to be volume depended.
If the Volume slider is full I don´t here any artifacts
but if the volume slider is for example half it the decay it really weird for all 8 voices on that board.
The decay randomly dies.

Trying to look at the service manual
but what exactly IC is the volume fader adressed to and what happens there before the CEM 3387 and SSM2300(changed all them without any difference)
 
Help please.

[mg73]

seems like all CV to CEM3387 is weird,
for example filter sounds aliased when having a filter envelope controlling it
tried to change ad6012 with no result.

is there any idea changing IC5 or IC6?

Dr.C where are you?

[dr.c]

Dr. C is back in town...

There are somewhere ultra cheap circuits wich are the sample and holds for the filter values, etc... and they are crap. Evry damn manufacturer uses them, and they fail all the time.

Its a C-Mos circuit, genericlay called "4051" (CD04051, MC14051 ...)

Change this crap, but you will have to recalibrate your machine, using a UST diskette (Universal Sound Test) from E-Mu, and an excellent Vu-Meter.

[mg73]

Dr.C is back and my two "lost" EIII cpu boards are found
on the same day!!

Thanks for info will get right at it after my holiday in France(24/7 rain in Normdandie)

[dr.c]

Alleluhiah !!!

[mg73]

ok back and had another look on this problem.
The problem are the same on all 8 channels
And there is 8 CMOS 4053 for each channel
Could one faulty 4053 mess up all 8th

[mg73]

All eight channels on that board is faulty
It´s both panning,filter cutoff, etc.
It´s like that the controlling voltage for those
is quantized instead of smooth.

Any clue Dr.C?

[mg73]

Removed the last tree soldered IC´s IC5,6, and IC1(LF356)
and viola it works perfect.
Was so tired of removing and inserting this Output cards
so I changed all at once so unfortunately I don´t know
exact which one of them that was faulty(for others future problems)

But now it works.