Vintage Synth Repair

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

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@...
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"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)
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