ARP Quadra service notes

[Jonathan G]

A very interesting read indeed... especially as I am about to begin a Quadra restoration of my own!!!

Mine has many issues- only the lead section works and is the arpeggiator is stuck on, couple of keys don't work, and a couple of the membrane switches don't work.

For this reason I am considering just going through and replacing all the logic chips, possibly all the caps while I'm at it. I figure after this would be a good place to start trouble shooting!

Would anyone have any sources for a new front panel if I can't fix the membrane switches?

If three sections are out, I'd suggest looking at the mixer section. Also check the output of the filter board on the polysynth PCB. I forget which test point it is, but it's on the schematic. There's a quad op-amp that likes to burn out on there.

And, regarding a membrane fix, if you get desperate and aesthetics are not a major concern: http://www.marksmart.net/gearhack/arpqu ... draTop.JPG
Re-seating the ribbon cables may also help. That fixed the problem with some of the intermittent switches on my Quadra.

Good luck!

[lukeA]

Thanks so much for the info guys.

Kevin, thanks for your input. Particularly as I was getting ready to order something like the 100 or so logic chips in this unit!

As I said there are a few membrane switches out, however it changes programs ok, the LED's turn on and off, and the lead section appears to work as it should.

So you speak as if it actually may to be possible to repair the membrane?? I was led to believe that they are irreparable? How do you even access them? That would be awesome if possible. Otherwise yeah, I would be looking at some other options if I couldn't get them going. I'm lucky in that I may have a lead on a new front panel already. Just trying to make sure the membrane on that one is fine...

I will definitely get it up on the bench before I start ordering and replacing chips then.

Jonathon, Yes what you are saying about the mixer section makes sense. I was thinking that or something to do with control of those sections. Or the dividers as Kevin mentioned.

It is also likely that the ribbons may be responsible for some of the issues, in the small look I've had inside the unit I noted a tech had previously bypassed several ribbon connections by wiring hook up wire straight through.

The good things about this unit are that it has only had one owner since brand new, and also I recently noticed it has already been completely recapped with new lytics!! So half the work is done for me!!!

Thanks again guys. Haven't had much time to get stuck into it yet but certainly will be pretty soon. Keep you posted.

Luke

[lukeA]

Hi all,

I was trying to verify the function of my membrane, but I couldn't work out why my interconnect diagram didn't seem to match up to the synth... I have a hard copy manual which came with the synth, however the schematics are for a 2460 version while my synth is a 2461.

Does anyone know if there is a schematic available for the 2461 revision? I am having trouble matching up the connectors from the membrane to the CPU board, there seems to be a lot more on mine than the 2460.

Cheers,

Luke

[Kevin Lightner]

I have a partial manual for the 2461 and 2462.
Missing schematics, but has other pertinent info.

http://www.synthfool.com/docs/Arp/ArpQu ... e_text.pdf

[lukeA]

Thanks Kevin but I already have these- I received a printed manual with the Quadra which is 2461-2463 models, however the schematics included are still the 2460. Perhaps this means they only published these schems...

Guess I'll just work it out through trial and error.

Cheers

Luke

[rvince]

Found this link that could be helpful:

http://www.synthfool.com/docs/Arp/ArpQu ... matics.pdf

Robert