Vintage Synth Repair

Do you have the service manual? This is critical. If not, you can find a partial service manual here:

http://www.synthfool.com/docs/Arp/ArpQuadra/

It's actually missing a couple of pages, (a parts list and one PCB  diagram) but is complete enough, and if you need the missing page I have it. I am pretty sure this one has all the schematics. Also, most of the other copies of the manual you will find online will in fact be this scan.

I am having similar problems with my Quadra, with strings/poly section on certain sharps sounding wrong, and also one note not sounding at all, and I am pretty sure these are separate faults.

The Quadra poly synth section is based on the Omni, (and some of the service literature actually says Omni) and I haven't got around to working on mine, but started to look at threads re: similar issues with the Omni.

Sorry I can't be of more help at the moment. I'm not that much of a tech either. The Omni manual is also available at that same site above and I started to compare the two to learn about how the notes are produced.

--- In vintagesynthrepair@yahoogroups.com, martin.morgan@... wrote:
>
> HI all,
> 
> My 1st post to this group - been lurking a while.. :0)
> 
> Quadra question for you - Top C# (C#5) and only this one note is 
> misbehaving
> 
> On both the Poly & Strings sections when on the 4' setting, this note also 
> sounds the 8' setting note
> 
> On 8' setting the all the notes play as expected
> 
> Any one come across this sort of thing before?
> 
> Also one other observation is that the keypad itself is not a Pratt & Read 
> - is this a common thing with Quadra's?
> 
> Hope this makes sense!
> 
> Regards,
> 
> Martin
> 
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