Vintage Synth Repair

Hi Everyone and welcome.
     When I do repairs on synths, I will hold the keys down for a long time
to see if the EG is malfunctioning, If it starts to gradualy make a sound
then you know that the EG has a problem, Also the filter cutoff could be
below
audible level (all the way down) and so I try to control it with an LFO to
get some other control voltage to it. Of course the best thing to do is
trace
the signal with a scope. I had a Omni II and it was dead when I got it,
I had to replace the final stage op-amps to get sound out of it, these were
on the back vertical board in the synth. Try to look there.

Hope this helps.

Gerry Dahl

Keep on Moogin'

----- Original Message -----
From: Brian Andrew Marek <bmarek@...>
To: <vintagesynthrepair@egroups.com>
Sent: Thursday, August 03, 2000 4:35 PM
Subject: [vintagesynthrepair] Brian reveals his Omni problems!


> First, the good bits:  the LED's light up, the power supply is kicking
> out a nice, healthy 15 volts, the filters work, all the keys apparently
> work in the sense that there is an audible click when they are pressed
> and one can hear a low-volume swirl of white noise when they are
> depressed.
>
> The bad news:  No string or synth tones.
>
> What I've already done:  Replaced all those nasty tantalum capacitors.
> Replaced several 1458's.  Replaced virtually every component in the
> oscillator circuit.  Replaced the 4007 on the upper voicing board.
> Replaced a number of 3904 and 3906 transistors.  Replaced a bunch of
> other comonents that aren't usually mentioned in conversations like this
> but I had a hunch they were questionable.  Checked the integrity of many
> connector ribbons and solder traces.
>
> And yet, in spite of all this... it will not play.
>
> Are there any other Omni repair panaceas that I have neglected to
> attempt?  Obviously there's something wrong somewhere between the
> oscillator and the filter.  But what???
>
> BaM
>
> --
> Find out more about Rocket Park at the (subliminal banana) home page!
> http://www.rocketparkmusic.com/
>
>
>
> 
>
> To unsubscribe from this group, send an email to:
> vintagesynthrepair-unsubscribe@egroups.com
>
>
>