Awhile back I got my hands on a model M 1391401 & dated Sep 89', my first proper 'old' mech keyboard. It didn't have a cable but it was still relatively cheap.
I ordered the SDL to USB cable from ebay and when it arrived & I plugged it in I found out that this keyboard might have a slew of issues... and might be possessed.
Here's my KeyTest result(of course no win/menu keys):
So besides the ENTIRE left side of the keyboard not working, both shifts don't work and also the keypad multiply & minus keys aren't working. Beyond the key issues, all three of the lock-lights aren't also working, however they do toggle on and off except for the capslock.
Here's another weird thing about the keys: there's actually ghosting. I've searched far & wide and have never seen any ghosting issues with any model Ms, but this one has some... also with the non-working keys no less. here's a list of what I could find:
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F2 + F4 + F5 = F9 F3 + F4 + F5 = Backspace F3 + F4 + F6 = ] 2 + 4 = V W + R = V S + F = V and probably more, but that's all I could find atm
So I opened the board, with hopes that the ribbon plug might be the issue as it seems to be a common problem and an easy fix, but it all looked fine. Here's a dump of pics,
- Can the cable be the issue? this is the cable that I got: https://www.ebay.com/itm/USB-to-SDL-6-P ... 3062450516 There have been no compatibility issues with it or any complaints, possibly I got a faulty cable? he does mention he tests every cable so I'm doubtful this is the issue. I have also tried plugging in different USB ports with the same result.
- I think the next logical step would be to open up the metal & barrel plate and check the membranes, of which I'm worried of doing. I'm not even sure what I'd be looking for if I'd open it up. I do have the tools but I don't have the hardware or the experience of doing so and I don't wanna ruin the barrel plate. I'd also have to reuse the membranes as I no longer have the means of buying any replacement membrane sheets.
- One thing I noticed is that the broken keys seem to be on the same 4 rows, as opposed to being random keys. This makes me think that it might not be water damage, but rather lines on the circuit.
- is there a possibility that it's the controller module? I honestly don't know what to look for. It just looks like none of the connections are wearing out, none of the electric-y looking bits look like they're burned or blown up.
Apologies for the lengthy post, I just wanted to be thorough & include as many details as I can. Any advice/help appreciated!