Vintage Synth Repair

Great thanks a lot..I will do..

Phil.

--- Peter Brown <pbrown@...> wrote:

> hi Philip, i have Omni schematics & other info that
> might be useful for 
> you on the "ARP Omni Resource Page"
> 
> http://peterunderdog.com/arp/
> 
> i did a lot of work on my Omni but it still has
> issues that keep it from 
> sounding as good as the demo recording - can't get
> the String Controller 
> to work right, and half of the bass section (16'
> bass synth and string 
> section bass) doesn't work...the tants are a
> definite problem - i 
> replaced mine w/aluminum electrolytics, which i
> later found out is 
> probably not a good idea (i.e., should replace w/new
> tants)...however, 
> it sounds better now than it did w/the old tants and
> an old weird note 
> sustain problem that existed when i got the synth in
> "the 80s" (i.e., 
> 1980 :-) was apparently fixed in the process
> 
> if you find out any interesting info, let me know &
> i'll post it on my 
> page...thanks, PB>>
> 
> Philip wrote:
> > 
> > 
> > Cool...thanks for that...yeh I seem to remember
> > something about the tants being a problem in that
> > model.
> > 
> > Well I managed to fix a dead Quadra so I feel I
> could
> > have a go at one of these..:)
> > 
> > Phil.
> > 
> > --- Malte Rogacki <gacki@...
> <mailto:gacki%40gacki.sax.de>> wrote:
> > 
> >  > At 17:08 Uhr +0100 08.05.2008, Philip wrote:
> >  > > On the subject of arp stuff..Ive been
> thinking of
> >  > > getting an Arp Omni but how come nearly every
> >  > single
> >  > > one I see is broken, not working, in need of
> >  > repair
> >  > > etc?
> >  >
> >  > There has been some discussion about this in
> the
> >  > past few days. Some
> >  > components inside the Omni are prone to
> failure.
> >  >
> >  > Here is a good description of the two typical
> >  > problems:
> >  >
> >  > http://www.oldcrows.net/~oldcrow/synth/tips.txt
> 
> > <http://www.oldcrows.net/~oldcrow/synth/tips.txt>
> >  >
> >  > The Omni uses quite a number of series 4000
> CMOS
> >  > chips; and also a huge
> >  > number of tantalum caps. The one I'm currently
> >  > trying to fix had a number
> >  > of those chips and a number of those caps
> blown. The
> >  > chips are very cheap;
> >  > and I substituted electrolytic caps for the
> tantalum
> >  > caps in the gating
> >  > circuit. This got me about halfway to a working
> Omni
> >  > - all voices produce
> >  > sound now; and the gating circuits basically
> work
> >  > (there are still some
> >  > other problems, though).
> >  >
> >  > Anyway, it's a totally great sounding poly
> ensemble
> >  > synth. The sound of
> >  > those divide-down synths certainly is something
> >  > special.
> >  >
> >  > The parts are cheap and mostly generic. I'm
> still
> >  > learning all this stuff
> >  > but I consider the Omni one of the easier to
> >  > understand synths,
> >  > circuit-wise. So if you want to learn to fix
> >  > something a cheap non-working
> >  > Omni might be a ticket.
> >  >
> >  > --
> >  > Malte Rogacki gacki@...
> <mailto:gacki%40gacki.sax.de>
> >  >
> >
>
----------------------------------------------------------
> >  > "Don't forget to TURN ON THE SYNTHESIZER. Often
> this
> >  > is the reason why you
> >  > get no sound out of it." (ARP 2600 Owner's
> Manual)
> >  >
> >
>
----------------------------------------------------------
> 
> 
> -- 
> Peter Brown
> office: (413) 577-2747
> cell: (413) 687-8287
> AIM: pb0000math
> 
> 



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