Hi @hasu,
Some actual news for this – finally. (and also big thanks to @svaya for sending a PS2 adapter which really helped this process.)
(Spoiler alert: this was a lesson in Occam's Razor if I ever saw one...)
I performed a number of tests for this board today, knowing that the specific adapter I was sent
worked on another Copam K-430. I did a number of tests (10+), but to my dismay I could not get it working, after swapping around the various adapters I have (the Soarer, TMK, Aten AT/PS2 + two generic AT/PS2 adapters)
Then,
*just after I was about to give up, keys started registering(!)*. I had moved the keyboard around a number of times during testing, and it turned out that once it had some weight on the internal 6-pin connector – when the cable was indirectly being pressed down because the heavy curled-cable was helping it due to the keyboard placement (hanging off the back) – it had contact. Color me stunned.
Now, I've looked at the whole PCB several times to check for loose solder joints, especially for the cable, but all were solid. (Also applied DeOxit on all contact points.) Turning to a magnifier glass to look closer at the bottom side of the internal 6-pin cable, it appears that one of the cable pins (the blue one) inside the internal connector facing the PCB-side did not have proper contact as the metal had moved slightly up (the part touching the stiff pin on the PCB connector).
I then proceeded to pressing down on the metal part (top-side) with a very thin screwdriver and (re-)applied DeOxit (done a number of times before on the PCB), and I then re-tested the board with my other adapters. And – (to my amazement) the Soarer registered every key – except PrintScrn – (albeit, and unsurprisingly, with an error code, as reported by others). The other adapter I bought, which looks similar to the generic one I just received *also worked*.(!) – every key registered, except the Scroll Lock, but I think that behaviour is a little special on this board.
Finally, I tested the TMK adapter and it (
*drumroll*)
also worked as well (!!) (scroll lock registered on this one, but for some reason
not the Print Screen key), which works on the generic PS2 adapters (with a passive AT-to-PS2 plug). So @hasu, it turns out that your adapter had indeed worked all along, and I owe you a bit of an apology for not noticing this problem earlier. You were also right regarding the hardware issue.
I am still quite stunned (and frankly moderately embarrassed) that it actually was a matter of
one pin inside the plug having intermittent contact, and that your adapter worked all along. But at least all the testing was not for nothing.
I think if I did not have the “known-working” adapter I would not have spent such a long time re-testing it (approx. an hour this time), and probably not noticed this silly cable problem; which finally explained why the keyboard was working earlier. Also interesting was that the Aten adapter (more expensive, did
*not* work, and it behaved as when I tried the NTC keyboard in XT-mode (all LED lights flickering, same as for the NTC)
What is also funny (or perhaps, scary) is that this issue would probably not even have been noticed either if the top case was mounted on the keyboard (due to the downward pressure it would cause on the 6-pin cable, similar to pressing down on it slightly with a finger). Since I was restoring the keyboard, the case had been removed, as well as all the keycaps.
So, bottom line, the persistence paid off. I frankly thought that there was little hope for this board at this point. Now I have to decide how to solve the (non-existing) AltGr key, so that special keys can be used probably by remapping another, and look at why the PrintSrcn key does not work (both on the Soarer and the TMK), but curiously registers on the PS2 adapters.
But that issue is somewhat minor compared to the problems experienced earlier with the K-430...
