Vintage Synth Repair

Hi,

Hi,

I just stumbled upon this list looking for information on this old 
wurlitzer organ, nearest I can tell it's a 1973 model and contains 
the orbit synthesizer section, someone was throwing it out and the 
3rd tier labeled "synthesizer" and it's little pot controllers 
(attack rate, sustain, modulation,etc.) as well as the built in 
leslie intrigued me enough to take it home.  Seems to work ok, except 
for the orbit sythesizer section.  I know very little about 
electronics but am trying to learn.  Only a few keys on the 
synthesizer will sound when you hit them , and all the sounds are 
totally bizzare, like white noise sometimes or just strange random-
unplesant sounds, really screechy and loud.  Are the oscillators 
screwed up, out of tune?  Hopefully this is something simple. 

Have some parts from a thomas "catalina" model organ which would send 
in trade for advice, particularly the pedal/amp/vibrato assembly 
which has the leslie out jack.  Other stuff possible too (sorry the 
leslie and bandbox are already gone).  You pay postage.

Thanks,
Ed

The Wurlitzer Orbit 3 synth that was built in to the Funmaker and 
other models of their organs was one of the first synths to utilize 
LSI(Large Scale Integrated) circuits.  These early LSI circuits were 
very very static sensitive and easily damaged.  Your description of 
the sounds it's making sounds like the LSI is blown.  It could be 
contact problems as well.  If you haven't already tried cleaning the 
switches and key contacts try doing so.  Be sure to ground youself 
first by touching some part of the metal chassis or use an ESD
(Electro Static Discharg) wrist strap that can be connected to the 
chassis.

Doug T.

--- In vintagesynthrepair@y..., ehallborg@y... wrote:
> Hi,
> 
> Hi,
> 
> I just stumbled upon this list looking for information on this old 
> wurlitzer organ, nearest I can tell it's a 1973 model and contains 
> the orbit synthesizer section, someone was throwing it out and the 
> 3rd tier labeled "synthesizer" and it's little pot controllers 
> (attack rate, sustain, modulation,etc.) as well as the built in 
> leslie intrigued me enough to take it home.  Seems to work ok, 
except 
> for the orbit sythesizer section.  I know very little about 
> electronics but am trying to learn.  Only a few keys on the 
> synthesizer will sound when you hit them , and all the sounds are 
> totally bizzare, like white noise sometimes or just strange random-
> unplesant sounds, really screechy and loud.  Are the oscillators 
> screwed up, out of tune?  Hopefully this is something simple. 
> 
> Have some parts from a thomas "catalina" model organ which would 
send 

> in trade for advice, particularly the pedal/amp/vibrato assembly 
> which has the leslie out jack.  Other stuff possible too (sorry the 
> leslie and bandbox are already gone).  You pay postage.
> 
> Thanks,
> Ed