What to do with mushy voyager snap domes?



#9

I have a 12C and 16C, each with one mushy key. I opened the 12C today (I'm using my 12C for practice and will crack open the 16C later if everything goes well) and un-staked the PCB, expecting to find a puncture in the little rubber pad between the back of the keys and the snap domes. The rubber pad turned out to be fine, but the snap dome behind the FV key feels weird. It doesn't have as pronounced of a snap as the other domes, but otherwise it looks fine.

What would cause a snap dome to go mushy and is there anything I can do to fix it? If there's no simple fix for the bad dome, I was thinking about trying to cut the bad dome out and switch it with the pristine dome at the bottom of the enter key. Are the domes simply taped above the proper spot on the PCB?

I would really appreciate any advice on how to proceed here.

Thank you!


#10

Quote:
I have a 12C and 16C, each with one mushy key.

Which key(s) out of curiosity?

Quote:
What would cause a snap dome to go mushy and is there anything I can do to fix it?

Fatigue of the dome due to normal cycling or improper/defective
actuating probe in the keycap. Domes are stamped to precise
geometries and when worn out need to be replaced.

Quote:
Are the domes simply taped above the proper spot on the PCB?

The domes used in a voyager are unique IME as they are packaged
as 5 domes on a carrier strip which happens to correspond to
a key matrix scan row. Electrically the carrier is redundant
and likely exists just to ease dome placement during
assembly as the carrier strip mates with adjacent heat stakes.
But a 8.5~9mm isolated dome will work as well. Conventional
snap domes are normally mounted to a pcb with no more than an overall polyester adhesive sheet.


#11

i'd be inclined to swap a whole strip of 5 domes from a beyond-repair donor 12C (completely dead, broken screen or damaged case), which can likely be purchased on ebay for very little. although the strip joining groups of 5 domes together serves no electrical purpose, my gut feeling is that it does help stabilize the dome location - perhaps contributing to the exceptional lifespan of the original voyagers.


#12

My current 12C could become the donor for my 16C (I have a 12C+ so I hardly ever use the original anyway), but first I want to see how solid it feels once I get it back together. If it's really bad I will probably just live with the mushy 5 on my 16C.

#13

Quote:
Which key(s) out of curiosity?

FV on the 12C and 5 on the 16C.

By the way, uhmgawa, was it you who posted dissembled 12C+ pics in another thread? I remember seeing them recently but couldn't find them again when I went to look. I'm wondering if adding one of those rubber pads from an old voyager could improve the key feel on the 12C+/15C LE (seems like it could dampen the hard click).


#14

Quote:
FV on the 12C and 5 on the 16C.

Interesting. Not keys I'd expect to see high cycle usage.

Quote:
By the way, uhmgawa, was it you who posted dissembled 12C+ pics in another thread? I remember seeing them recently but couldn't find them again when I went to look.

Yes, they are here hp12c_plus_teardown but
I've also copied them to flickr.com which I found to be a
bit more linux usage friendly.

Quote:
I'm wondering if adding one of those rubber pads from an old voyager could improve the key feel on the 12C+/15C LE (seems like it could dampen the hard click).

The more pronounced click in the sam7l voyagers is due to
use of a cut, 4 legged dome. Perhaps to ease pcb routing or
perhaps it was thought to be an improvement. It isn't IMHO but
they are selling just fine anyway. Actually the primary motivation
for the dismembered 12c+ above was upon first acquiring one
I puzzled what HP did to the keypad which resulted in such a
hollow, economical tactile feel.

Note the 12c+ does have a rubber pad over the dome's adhesive
sheet.

#15

I've done successful dome swaps on 41c calcs, so I presume the voyagers are similar. On the 41c, a sheet of sticky plastic film covers the domes, I simply peel it back, replace the dome with one from a donor calc, and put the sticky plastic back.

Cheers,
John


#16

Looks like its the same on the voyagers. I will try the same approach.

Thanks for sharing, everyone!


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