Vintage Synth Repair

Update: Fault no3 fixed...was an open transistor Q22 on the lower 
voice board. It's in the 8' Bass wave shaper circuit. 

3 faults to go!

One thing ive discovered pouring over these terrible quality PDF's is 
that the Omni and the Omni 2 have a fairly fundamental difference I 
don't see mentioned on the net anywhere.. The omni has the Bass synth 
8' and 16' sounds routed through the 4075 filter same as the the main 
synth section.

The omni 2 bass has it's very own seperate filter and a more complex 
envelope generator that both reside on the Omni 2 unique 'Bass Voice' 
board. They are both fixed sadly.

This totally changes the sound between the two. I can see why they 
did it but the bass sounded great running through the 4075 filter. I 
miss that. But I suppose it makes it more flexible in the long run.

What they should have done was put in another fully adjustable 4075 
just for bass...that would have been awesome...hmm future mod maybe?

Phil.



--- In vintagesynthrepair@yahoogroups.com, "eggwheatis" 
<eggwheatis@...> wrote:
>
> Hi guys, finally decided to work on my Arp Omni 2...wow this thing 
had 
> so many faults I dont where to start...actually I give you a write 
up 
> later! Basically it was a dead pile of boards. Nothing worked.
> 
> But anyway now I've got a few faults left I could use help with, I 
dont 
> have original schems and the PDF's on line are terrible, so If 
anyone 
> has a better copy let me know!
> 
> Faults:
> 
> 1: Strings slow attack setting only works on the first note or 
chord 
> pressed, you have to wait for all the notes to have died out before 
it 
> works again, other wise you just get fast attack.
> 
> 2: 8' Bass and Cello are much quieter than 16' bass and String bass.
> 
> 3: In the synth section if you set a short release and play one 
note 
> and let go of the key the release is perfect, however if you play 
more 
> notes after that you hear the tail of the previous notes in the 
current 
> note played..if that makes sense?
> 
> Basically it sounds just like youve got a long release set all the 
> while you're hitting notes.
> 
> 4: there is no top E to top C 4' sound produce from either the 
strings 
> or the synth section. It is kind of there but very faint.
> 
> Thanks, Phil.
>