Synth-DIY Yahoo! Groups Archives

Omni-2 Power Supplies

2003-09-13 by Dave Garfield

TGIF, persons!

Just a small note re: Omni-2 power supplies, if I may.  The 
*negative* side of the supply draws more current than the positive 
side.  I believe that, in order to balance DC levels, triggering and 
whatnot, Alan R. decided to generate negative-biased waveforms.  Oh, 
they look the same as a ground-to-positive wave... but, don't be 
fooled!  These start at Minus 15 volts, and climb all the way "up" 
to ground.  

Anyway, all keeding aside, I recall reading in my Service Manual 
that the current draw for the negative supply rail is greater than 
the positive side.  Just something to remember when troubleshooting.

OK.  Thanks for the forum!  

   Omni-logically Yours,
   Dave Garfield

RE: [vintagesynthrepair] Omni-2 Power Supplies

2003-09-13 by masada wilmot

Yup, lots of negative CMOS logic on the keyboard circuitry as I recall.

 

BTW, is "Dave Garfield" the "Garfield" of Dr Click fame? I'd love to get
hold of schematics for my wonderful Dr Click synch box (it works fine but I
like to have the docs for all of my old gear if possible).

 

mw

 

Interestingly from the schematic, the Omni PS uses sense lines. I haven't
seen power supply sensing used on many synth circuits. Does anyone know of
any other vintage machines with PS sensing? (I wish that the Prophet 5 had
better power distribution.)

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-----Original Message-----
From: Dave Garfield [mailto:daveogarf@...] 
Sent: Friday, September 12, 2003 10:56 PM
To: vintagesynthrepair@yahoogroups.com
Subject: [vintagesynthrepair] Omni-2 Power Supplies

TGIF, persons!

Just a small note re: Omni-2 power supplies, if I may.  The 
*negative* side of the supply draws more current than the positive 
side.  I believe that, in order to balance DC levels, triggering and 
whatnot, Alan R. decided to generate negative-biased waveforms.  Oh, 
they look the same as a ground-to-positive wave... but, don't be 
fooled!  These start at Minus 15 volts, and climb all the way "up" 
to ground.  

Anyway, all keeding aside, I recall reading in my Service Manual 
that the current draw for the negative supply rail is greater than 
the positive side.  Just something to remember when troubleshooting.

OK.  Thanks for the forum!  

   Omni-logically Yours,
   Dave Garfield

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Vintage Synth Repair

Omni-2 Power Supplies

Omni-2 Power Supplies

RE: [vintagesynthrepair] Omni-2 Power Supplies

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