I purchased an ARP Quartet as a project box. It needed some love and care. My difficultly was finding a schematic that was easy to read. The 2 that are on the internet are scans and are not the best quality. So I took to my spare time and went through the schematic and created my own schematic for this lovely instrument. If anyone has one of these instruments and would like the schematic let me know. It is still a work in progress as I am sure that many of the component IDs and values are not correct, but like I said, it is a work in progress.