This O2R turned up with dead channels and a few weird problems. Ignoring the few weird problems for now I took it apart looking for the obvious. (by the way these are a pain to get to the boards for the encoders)
You can now see the ADC board responsible for converting the analog signals into digital. This board uses AK-5390VP that is also equivalent to the CS5390 ADC chips.
On inspection of the boards I found this.
The desk as obviously taken a knock at some point and the PCB has cracked. After removing the board the track side also had obvious damage and a quick test with the multimeter confirmed no continuity for a few of the tracks. This kinda explained why most of the effected channels were on one side of the desk.
This isn’t a very good picture I know but if you look closely you can see that the tracks carrying the digital signals from the ADC chips as the tail end of the crack going through them.
With some very tedious soldering and gluing of wires I eventually restored continuity to all the broken tracks.
I also bridge the ground plane to restore ground to the far side of the PCB. If this was necessary Ive no Idea.
Well after all this I was hoping that the channels would all just come back life but as it is with these this its never that easy is it.
Stereo pairs 21 and 22 and pair 23 and 24 still did not work. Due to each pair sharing a ADC I decided that maybe the these had gone bad and pulled out the oscilloscope and the AK-5390VP datasheet . The signal going into the chips was fine but the outputs were completely dead. I removed these chips and fitted sockets waiting for replacements to come. The desk is now useable but missing the mentioned channels why I try and obtain these chips from a reliable source.
A bit of a update but I have also now confirmed these chips dead as I borrowed one from a working channel to check so sadly I may have to resort to china for parts. Parts for china can be a bit sketchy as they like to make a lot of fake chips that are no longer in production. Most of the time just removing the number off a similar part and selling it as something else.