[sdiy] Sv: ARP Pro Soloist strangeness continues!

[Daniel Araya]

A few month ago I asked opinions about a Pro Soloist that had the notes in the octaves *reversed" when you played.
I got a few replies and looked at the obvious...like connectors in the wrong way, shorts, bad sockets but no luck!

I decided to have another look at it yesterday and the keyboard encoder works fine according to the truth table in the manual but the D/A still outputs the highest voltage (+9V) at the lowest key and vice versa! The notes are somewhat out of tune  and the two highest keys have almost the same voltage out so that suggests something wrong with the D/A resistor network.
The signals on the first six resistors all seem ok but I'm unsure what the NAND-gates further down do. I'll try to swap them out tonight and see if that changes anything.

D/A schematic
http://farm4.static.flickr.com/3068/2547452021_09c5baab28_o.jpg

D/A circuit description (not that good)
http://farm3.static.flickr.com/2169/2547472603_53f9343f86_b.jpg

full schematics:
http://www.poconothermionics.com/arp.html


Any help or theories are greatly appreciated!

/Daniel