Author Topic: Trouble Diagnosing Key stickiness  (Read 265 times)

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Offline cmdshft

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Trouble Diagnosing Key stickiness
« on: Wed, 07 April 2021, 19:45:47 »
Hey all, noob here, I have a tofu65 that I just built. Here's the specs:

tofu65 alum purple
dz65rgb v2
gat ink black v2 (NK films + 205g0)
polycarb plate
durock v1 stabs (wires lubed with krytox xht-bdz, dummy's lubed with 205g0, also did the "plug the butt" thing I see others do)
KBDFans stab pads

Okay, so the issue I am having is that the left shift and the enter key seem to get "stuck" very briefly before returning up. I thought it was the keycaps being warped because I bought them from Amazon as a temporary set. So, I bought the PBT Notion set from NovelKeys_ and the same keys are getting stuck in the same manner. I took the keyboard apart and saw that there was some of the xht-bdz on the stab pads, so I cleaned it all up as best as I could, relubed the stabs and had the same results.

I'm not sure what to do, to be honest. I do not like how it feels and am not really sure what to do about it. I am 100% certain I am lubing them correctly. I have new v2 stabs and c3 stabs coming as well to try. Should I just stick with 205g0 on the stabs for everything?

Offline Leslieann

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Re: Trouble Diagnosing Key stickiness
« Reply #1 on: Wed, 07 April 2021, 21:13:05 »
It could be a lube issue but it can also be related to hot swaps.
Switches are meant to sit loosely in the holes and self center between the plate, pcb and stabs before being soldered into place, hot swaps don't allow them to do that and can cause bind, u using film makes it even worse.

Try those switches with just a common cap and see if they respond normal or if they still feel bind. If they respond normal, remove the switches and stabs, loosen the plate, reassemble then re-tighten the plate and check again before going further. If they bind with a common cap it could still be a plate alignment, but it could also be your film adding just enough to cause problems.
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Offline cmdshft

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Re: Trouble Diagnosing Key stickiness
« Reply #2 on: Wed, 07 April 2021, 23:26:00 »
Try those switches with just a common cap and see if they respond normal or if they still feel bind. If they respond normal, remove the switches and stabs, loosen the plate, reassemble then re-tighten the plate and check again before going further. If they bind with a common cap it could still be a plate alignment, but it could also be your film adding just enough to cause problems.

My board is apart right now BUT, I did some of that testing thankfully on my own. The switch is perfectly fine. It only sticks like this when I have the cap on that needs the stabilizers. It's such a quick "stuck" feeling, I'm not sure how to describe it. Once it unsticks, it returns back to the top like I would expect, no sluggish feeling. I'm willing to bet, personally, that the issue is I overlubed the dang stabs... And that's why the board is apart. I forgot these plastics do not like isopropyl alchohol.. and I certainly tried to clean out the lube with a cup of it and the stems fell right the heck off the body in the alch... So, tomorrow I have a set of Durock v2 stabs coming, so I will lube those up a lot more conservatively than I did before. I think by butt plugging with XHT-BDZ with a 0 brush I really mushed it into the housing of the stem, causing this sticking effect.

Offline Netkingtechnologies

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Re: Trouble Diagnosing Key stickiness
« Reply #3 on: Thu, 08 April 2021, 07:22:57 »
This is not a problem in increased "stickiness", it is a problem of ineffective insulation between the two conductive membranes. There are several problems with the keyboard manufacture that can cause this problem. One is a mis-registration of the different membranes making up the keyboard. While there are several mechanical pins to maximize registration, a slight warping of the bottom layer (which is stuck to a metal plate) can still occur. Even if not mis-registered, the slight buckling of the bottom membrane which results can cause a sticky key. This problem was addressed in pre-production, and hasn't been seen on dissected failing production units.

Another likely hypothesis is the spacing/insulating compound which is placed between the keyboard membranes is inadequate around certain keys. The bottom membrane contains a serpentine array of traces which are shorted out by contacts attached to the upper membrane during a key press. There is a printed pattern of rubbery glue which separates the two membranes and holds the contacts apart when the key is not pressed. This rubbery layer is laid out into 3mm wide linear traces between key rows, and as 2mm, diamond shaped dots, or 0.5 mm dots internal to the key. Most keys have an array of 4 contact dots with a 2mm, diamond shaped spot of glue directly between all 4 contacts. However the Ctrl, both Hand and Alt keys as well as the ] key have 6 contact dots with only two 0.5mm dots of glue to hold the contacts apart. The center pair of dots in the group of 6 have no glue dots at all between the upper and lower membranes and therefore may be more prone to failure.

Apparently these keys are the ones which are reported to stick the most often. In response, a new silkscreen mask for this compound has been prepared, which both decreases the available contact area and increases the size of the central spacing dots under the problem keys.

Online tp4tissue

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Re: Trouble Diagnosing Key stickiness
« Reply #4 on: Thu, 08 April 2021, 08:01:14 »
Lube can add friction if it's in the wrong place or of too high viscosity.

Use as little as possible

Offline cmdshft

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Re: Trouble Diagnosing Key stickiness
« Reply #5 on: Fri, 09 April 2021, 02:28:15 »
Okay. So I got the V2's in today, and as soon as I got home from work I began to operate.

I stuck with the XHT-BDZ lube again, but this time I made sure to really lube up the wires good before fully assembling the board. I tested over and over and relubed as necessary. I made sure to be EXTRA careful when assembling the stabs back together that I didn't get too much of the thick lube anywhere other than inside the dummy stem. I stuck with 205g0 on the stem housings.

I am happy to report that I no longer have sticking keys and the keys sound wonderful now under normal use. Under rapid clacking, two keys have an ever so slight tick... And I will fix it using a small syringe once they come in from Amazon. I will not use the brush method like I did before, which I believe put the lube in all the wrong places, causing the sticky feeling.

Thank you for your help and input! I can't wait to build more of these things.