Repair membrane keyboard silicone dome

I have a venerable Logitech G15 v2, the orange one, and the top rubber dome of the A key just broke. With the cap of a pen I sort of placed it again in a position where a click is normal, but I'd like to repair it, how could I do that? What kind of glue would stick to silicone? or maybe, can I cut the rubber dome of another keyboard and put it in place of the broken dome?

I've already looked into plenty of mechanical keyboards and none are even close of having the same features as this wonderful keyboard, but I'm considering one if the repair is not possible. One caveat is that I need a keyboard with Spanish layout and that limit the possibilities a great deal.

Pictures of the broken piece are below!

Edit to answer @fixer1234 questions:

Is the dome surface torn and you need to repair it or is the dome ripped off but intact and you need to glue it back in place?

Looks ripped off, glue should be enough.

The picture looks like a mechanical actuator. What is/was on the back of the dome (simple dome membrane vs. some protruding piece that pushes on something)?

It's not mechanical, it's the silicone nip that sit on top the sheet where the printed circuit is.

Was the dome an individual keycap or part of one large sheet of keycaps?

The dome is just broken for the letter A, but I'm not sure I understand this question.

Do you have another keyboard with identical domes, down to the size and shape and construction?

I have another Logitech keyboard with very similar silicone domes. But no, I cannot just swap the entire thing.

If all the keycaps are part of one sheet, can you disassemble it to remove the sheet?

Yes and yes, I'll do it this Friday and post more pictures of it.

Is it a clean tear or is more of the membrane falling apart?

A clean tear, if when I disassemble the keyboard see that the membrane is in too bad shape I'll have to get a new keyboard. :(

Edit: Alright, here are the pictures!

3 Answers

I had a similar problem, with the torn dome getting stuck down.

I first tried vulcanizing rubber from a bicycle patch kit. While it made a nice layer of rubber over the tear and could be strengthened by making multiple layers, it didn't stick to silicone well enough. It would start slowly coming apart from the silicone on each press on the dome.

Some generic glue behaved similarly. I'm guessing the approach of building a layer on top of the tear and the silicone is bad. Just gluing the tear back together would be better, but since the thickness is under 0.5mm there's not a lot for the glue to stick on.

What did work was cutting the torn dome top off and transplanting the same kind of dome under it. I left a bit of the sides of the original dome and didn't use glue or anything-- once it's installed, it stays there just fine. The result is a key that's a bit harder to press than the others but works just fine. Of course one key is missing because I needed the spare dome.

EDIT: I blogged about this with photos:

I'd recommend rubber cement. It will adhere to the membrane well and provides the flexibility needed for a keyboard. Get the membrane positioned as well as you can and put a nice clean layer of rubber cement on. I won't guarantee that it will feel exactly the same as every other key, but it should last you a little while until you get a new keyboard.

Use silicone adhesive: Dow 700 or Dow 734; the latter is flowable and might go where you do not wish. 700 is thixopropic and holds its shape. First clean and then prime with Dowsil PR-1200 prime coat red (it is pink). Allow 7 days cure for full strength.