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1 of the 6 Voice/Oscillator does not respond to filter settings. Help!!!

1 of the 6 Voice/Oscillator does not respond to filter settings. Help!!!

2014-02-13 by <novel0@ymail.com>

Hello to all, 

I have a problem with one of the 6 Voices/Oscillators on my Polysix. 

3rd Voice/Oscillator does not respond to filter settings. 

If I set cuttof to zero, one Voices/Oscillator remains unchanged. (The other 5 are filtered.)

If I turn the cutoff back to 10, I can realized that 3rd Voice/Oscillator sounds a bit dumfer as the other 5. With other words, he always stays the same unchanged.

I tried to calibrate it properly with reference to the manual but with no succes.

Maybe someone can give me a hint what can be broke and how can I fix it. 

Thank you and sorry for my English.

Re: [PolySix] 1 of the 6 Voice/Oscillator does not respond to filter settings. Help!!!

2014-02-13 by Bob Grieb

On the KLM 366 board, IC23 should be 4051/14051 demux for the cutoff control voltages to the SSM filter chips.    The outputs of this chip are stored on capacitors, and then buffered by op amps IC20, 21, and 22.   If you measure the voltage at the outputs of these op amps, you can see if all six of the voices are getting the cutoff voltage when you change the front panel cutoff control.  If all of these voltages are the same, then the problem would have to be after the voltage buffers.   If the SSM 2044 chips are socketed, you might try swapping two of them to see if the problem moves, or if its not the chip.  Be careful when doing this, since these chips are not easy to obtain.   And be careful not to bend any pins under when plugging the chips into the socket, assuming there is a socket.   The notch on the end of the chip tells you which way to plug it in.   If you plug it in backwards, it will probably be damaged.
 
    Hope that helps,
 
      Bob

From: "novel0@ymail.com" <novel0@ymail.com>
To: PolySix@yahoogroups.com
Sent: Wednesday, February 12, 2014 4:18 PM
Subject: [PolySix] 1 of the 6 Voice/Oscillator does not respond to filter settings. Help!!!

 
Hello to all, 
I have a problem with one of the 6 Voices/Oscillators on my Polysix. 
3rd Voice/Oscillator does not respond to filter settings. 
If I set cuttof to zero, one Voices/Oscillator remains unchanged. (The other 5 are filtered.)
If I turn the cutoff back to 10, I can realized that 3rd Voice/Oscillator sounds a bit dumfer as the other 5. With other words, he always stays the same unchanged.
I tried to calibrate it properly with reference to the manual but with no succes.
Maybe someone can give me a hint what can be broke and how can I fix it. 
Thank you and sorry for my English.


Re: [PolySix] RE: 1 of the 6 Voice/Oscillator does not respond to filter settings. Help!!!

2014-02-14 by Bob Grieb

Great. Glad you found the problem.
 
   Bob

From: "novel0@ymail.com" <novel0@ymail.com>
To: PolySix@yahoogroups.com
Sent: Thursday, February 13, 2014 2:33 PM
Subject: [PolySix] RE: 1 of the 6 Voice/Oscillator does not respond to filter settings. Help!!!

 
Thank you Bob one more time for this hint. I have fix it!  It was broken pathway from IC 22 to 3rd voice.