Vintage Synth Repair

Check the colored cables interconnecting the two voice boards; two are strait, one is twisted. I had this problem on mine, and I spent a lot of head-scratching before nailing it.

Francois

--- In vintagesynthrepair@yahoogroups.com, "Paulo Palmieri" <paulopalmieri@...> wrote:
>
> Yes, that´s the right ways to solve the problem!
> 
>   ----- Original Message ----- 
>   From: jammie 
>   To: vintagesynthrepair@yahoogroups.com 
>   Sent: Sunday, November 11, 2012 7:44 AM
>   Subject: Re: [vintagesynthrepair] ARP Omni MK1 - no sound, must be something stupid
> 
> 
>     
> 
>   but you are right he should check that cap as he might of done a cold solder joint
> 
>   he will know once he has done the check on pin 12 of the cd4007 chip
>     ----- Original Message ----- 
>     From: Paulo Palmieri 
>     To: vintagesynthrepair@yahoogroups.com 
>     Sent: Sunday, November 11, 2012 9:38 AM
>     Subject: Re: [vintagesynthrepair] ARP Omni MK1 - no sound, must be something stupid
> 
> 
>       
> 
>     Sorry, I didn´t read the messages below...
> 
>       ----- Original Message ----- 
>       From: jammie 
>       To: vintagesynthrepair@yahoogroups.com 
>       Sent: Sunday, November 11, 2012 7:13 AM
>       Subject: Re: [vintagesynthrepair] ARP Omni MK1 - no sound, must be something stupid
> 
> 
>         
> 
>       he said he replaced all the tantalum caps
>         ----- Original Message ----- 
>         From: Paulo Palmieri 
>         To: vintagesynthrepair@yahoogroups.com 
>         Sent: Sunday, November 11, 2012 9:07 AM
>         Subject: Re: [vintagesynthrepair] ARP Omni MK1 - no sound, must be something stupid
> 
> 
>           
> 
>         There is a tantalum cap there in the oscillator around the MK5024 that kills the oscillator. It´s common issue finding this cap shorted.
> 
> 
>           ----- Original Message ----- 
>           From: jammie 
>           To: vintagesynthrepair@yahoogroups.com 
>           Sent: Sunday, November 11, 2012 6:26 AM
>           Subject: Re: [vintagesynthrepair] ARP Omni MK1 - no sound, must be something stupid
> 
> 
>             
> 
>           first thing set you oscilloscope to the master oscilator 
> 
>           and make sure your getting a square wave
> 
>           put it on pin 12 of the cd4007
> 
>           this then goes to the top octave devider chip
> 
>           mk5024
> 
>           if you have no square wave generated here you will not get any output at all
> 
>           if you have a square wave
> 
>           then test the top octave devider chip pins 4/5/6/7/8/9/10/11/12/13/14/15/16
> 
>           these are the square wave signals for the each key note
> 
>           if you dont have square waves at these pins then the top octave chip is crapped
> 
>           these are the first 2 places to look as seeing you have changed so many items on this synth
> 
> 
>             ----- Original Message ----- 
>             From: Mark 
>             To: vintagesynthrepair@yahoogroups.com 
>             Sent: Sunday, November 11, 2012 5:00 AM
>             Subject: [vintagesynthrepair] ARP Omni MK1 - no sound, must be something stupid
> 
> 
>               
>             I am in desperate need of some direction! I picked up a broken ARP Omni MK1 last year on craigslist as a project, because of the success I had read about online of people bringing them back from the grave.
> 
>             There is no sound at all coming from this synth! I am a DIY hobbyist, but not much of a schematic jockey, so I have tried to restore and overhaul the Omni. The lights light up and the switches turn the lights on and off. The power supply is spitting out -15 and +15 like it should, just no output from the main out, synthesizer out, or any other out.
> 
>             You guys are going to laugh.
> 
>             I replaced the following:
>             -All tantalum caps, decoupling and envelope
>             -All CD4XXX ICs, on every board (yes, I have WAY too much time)
>             -LM1458s on string control board
>             -LM301 on filter board
> 
>             Now I am at an impasse. I really want this thing working with a passion, and getting rid of it this far in the game would be a big mistake. Is there any part of the synth I should be looking at? I have an oscilloscope, should I be probing a certain place? I've worked on smaller, less complicated synths in the past, but the Omni is damn near confusing.
> 
>             One last question: The phaser board connector was upside down when I received it. Is there anything that could fail on the phaser board that would cause it not to make any sound?
> 
>             I truly appreciate your help, thank you so much for your time!!!
>