Repair membrane keyboard silicon 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!

Deses

Posted 2016-09-07T20:14:32.663

Reputation: 222

Pretty much any industrial glue will work. There are hundreds of brands, pick the one you can afford. Your "censor" job made the image basically unhelpful.

– Ramhound – 2016-09-07T20:23:33.880

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? 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)? Was the dome an individual keycap or part of one large sheet of keycaps? Do you have another keyboard with identical domes, down to the size and shape and construction? If all the keycaps are part of one sheet, can you disassemble it to remove the sheet? Is it a clean tear or is more of the membrane falling apart? – fixer1234 – 2016-09-07T21:20:16.637

@Ramhound Sorry for the picture not being helpful, I'll disassemble it this Friday after work to clean it (it's due time anyway) and post more pictures. – Deses – 2016-09-07T22:35:17.630

@fixer1234 I answered to your questions in an edit above. – Deses – 2016-09-07T22:47:40.613

Pictures added! – Deses – 2016-09-11T14:00:20.307

1A membrane keyboard typically has a material like graphite embedded in the surface that contacts the sensor traces when the key is pressed. This sheet doesn't, so I assume this just provides the mechanical action for the key and there is another layer that actually makes the connection. We're looking at the sheet right side up and pressing the key pushes the torn part together rather than push it apart? Does the key snap onto the ring at the top (the part that's torn)? If so, this will be a tough repair that would need to be made on the underside and without interfering with the action. – fixer1234 – 2016-09-11T19:52:28.757

2(cont'd) You won't be able to match the strength and mechanical characteristics of the dome. Best case, you may be able to keep the key from flopping around as long as you don't pull on it. There isn't much that will adhere to silicone rubber, especially that is constantly being flexed. Best bet is silicone adhesive. Thoroughly clean the area to be glued with isopropyl alcohol. Look at clearances to see areas you need to avoid and the available glue thickness. Don't bother trying to glue the torn edges together. You can't do anything useful and you will keep them from mating. – fixer1234 – 2016-09-11T19:53:32.387

1(cont'd) Use a small applicator to spread a thin layer of silicone to create a collar completely around the underside that connects the torn pieces. Let it cure for a day before reassembly. Be delicate in attaching the keycap and gentle in using that key. Don't try to remove the keycap again or the repair will tear. I wouldn't expect the repair to last very long; maybe to tide you over until you replace the keyboard. – fixer1234 – 2016-09-11T19:54:22.540

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: https://hannuhartikainen.fi/blog/keyboard-dome-repair/

StackExchange saddens dancek

Posted 2016-09-07T20:14:32.663

Reputation: 594

2Thanks! If I understood you correctly, I did the same. I cut the dome from another keyboard and place it near it, and it holds pretty ok. The feeling is different but I can live with it. – Deses – 2018-08-12T22:59:10.267

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.

tbenz9

Posted 2016-09-07T20:14:32.663

Reputation: 5 868

Hi @tbenz9! Thanks for the answer. I've added better pictures now. I searched for rubber cement here in Spain but looks like it's banned due its toxicity! What alternative would you recommend? Lockite Super Glue is readily available, but I fear it will make the key too hard. I also have plastic glue from a model kit plane. – Deses – 2016-09-11T14:05:19.587

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.

Edward Dimen

Posted 2016-09-07T20:14:32.663

Reputation: 1