Cherry G80-1800 HPU -- problem with alternating non-working keys

[voided]

Hi all,

I've recently picked up a G80-1800 HPU which looks quite nice but seems to have an electrical problem. A number of keys are not registering. What is striking is the pattern of working and non-working keys. Across the QWERTY and ASDF rows, exactly every 2nd key is working.

I wonder whether someone here may have any ideas about the possible cause of such an issue. Should I be looking at the switches, the PCB or the controller? I'm moderately handy with cleaning, soldering, disassembly/assembly, etc. but my knowledge of keyboard electronics and logic is sadly very lacking.

My thanks in advance for any wisdom you can share.

ps. I can do hi-res photos if this would help.

[dorkvader]

Sounds like a few columns might be out. I recommend opening it up and checking for breaks, bad solder joints and the like.

Pictures of the PCB underside may help as well.

If it has diodes, you can check and see if they were installed correctly. Maybe a previous owner modded it the wrong way? probably not, but you can look at them without even opening it. If it's got jumpers then don't bother ofcourse

[IvanIvanovich]

Most likely cause is you have revision with the ****ty switch to controller connector cable. These often come loose in transit and do exactly like you say. It's no trouble to reseat it, but it is likely to happen again when moved much. Or you can fix it forever by removing the sip sockets and soldering in the cable permanently.

[dorkvader]

Most likely cause is you have revision with the ****ty switch to controller connector cable. These often come loose in transit and do exactly like you say. It's no trouble to reseat it, but it is likely to happen again when moved much. Or you can fix it forever by removing the sip sockets and soldering in the cable permanently.

I thought the g80-1800 had a plug-in type controller like the 11800s do. That's why I didn't mention it.

Man I hate those cables.

[voided]

Thank you both for your suggestions. I went to have a closer inside. Looked for a connector cable to the switch (which I assumed to mean the "AT/PC" switch, but was not sure). This one appears to be soldered. I also noticed a few issues with corrosion on the circuit board. After taking some macro photos of these I noticed what I now suspect is most likely to be my problem: cracks in the PCB. These were very hard to see initially with the naked eye. Various photos are attached.

I guess the question becomes: would every place where a crack goes through a trace kill continuity? Or only the really bad ones, like the spot highlighted by the topmost arrow in my last picture? Does it work to scratch away the coating and test with a continuity meter?

And, I suppose, depending on where the answers go, is there any value in this board non-working? The doubleshot keycaps, perhaps?

[dantan]

looks old. Is it deteriorated? There seems to be air bubbles under the pcb

[voided]

Those pale patches seem to be where something (water/minerals?) has eaten into the glossy surface of the coating, leaving a matte finish.

As for how old the board is, appears to be from 1992 if I am reading the date imprint on the case properly.

[dorkvader]

I had a cracked cherry PCB once. It's one reason I think cherry can't make a decent keyboard to save their life!

Anyway, it's usually only the "worse" cracks that cause a break in continuity. You can check this for sure with a multimeter. (or battery / LED continuity tester)