15C Keyboard Issues [UPDATE- DO NOT EMAIL ME]



#5

Hello,

The support team now has received enough units to analyze. They now ask that if you have an issue, please go through the normal support process.

Thank you to those that contacted me and sent back units!

TW

--

Although I work for the HP calculator group, the thoughts and comments expressed on this forum are my own.

Edited: 30 Sept 2011, 12:18 p.m.


#6

Thanks, Tim and HP, for immediately addressing the keyboard issue - even with the HHC2011 event occurring during the HP 15C LE roll out.


#7

And what exactly was addressed? I thought contacting support people was the only option anyway and nothing has been added. I see no official confirmation/admittance that the keyboard has issues.

Wouldn't be better if the support team disclosed their findings?

With 12% failure rating I think HP should be a lot more specific about the problem.


#8

Quote:
The support team now has received enough units to analyze.

Tim said they had enough units to analyze, not that they were done analyzing them. While this may seem like a "simple" problem, nothing is simple in industry. They'll probably have to disassemble a bunch of calculators, try to figure out why the keyboards don't work, figure out how to correct that, and then deal with the factory to make sure future units don't have this problem. I think I have a pretty good idea of what the issue is, but I'm not a mechanical engineer, nor do I know anything about HP's keyboard design so what I noticed could just be a coincidence or one isolated case.


#9

Yea, I know what Tim said, I was wandering why the excitement, just because some people did their job?


Quote:
I think I have a pretty good idea of what the issue is, but I'm not a mechanical engineer,


Would you speculate on this a bit?


#10

I had a 15C with a bad divide key. It clicked, but didn't register unless you pushed it hard. I decided to open the back since they're not too hard to disassemble and discovered that if you held the PCB and the front case together, the key worked fine. Closer examination seemed to show that the heat stake closest to that key wasn't melted down far enough.


#11

That's interesting, thanks for sharing. But is there such a heat stake close to the "." key (my case) and could you fix the problem yourself?

Cheers,


#12

Unfortunately I do not remember. It could be possible to carefully remelt the heat stake yourself, but I really wouldn't recommend it on something this new under warranty and with a known defect.


#13

Me too, thanks.

#14

the trick would probably be to make up a jig to hold down the PCB firmly, then place a drop of 2-part 24hr epoxy resin glue over the faulty stake, such that it would run down and around, and fill in the gap.

BTW, has anyone got photos of a disassembled 2xCR2032 HP-12C showing the actual keyboard construction/design. had a bit of a look with google, found various comments from 'experts' but no actual photos.


#15

Quote:
the trick would probably be to make up a jig to hold down the PCB firmly, then place a drop of 2-part 24hr epoxy resin glue over the faulty stake, such that it would run down and around, and fill in the gap.

Heat stakes are no one's friend and are mainly a concession
to cost reduced assembly. A malformed stake might just be
a sign from above to rid the calc of them altogether and
secure the pcb to the housing with screws. Doing so results
in a serviceable keyboard and more flexibility in modifying
the pcb.

Assuming the 15c le stakes voids are identical to the 12c+, an
M1.2 screw is about the correct size to self thread the core.
For a 12c+ stake cut flush with the pcb surface the resulting
core void depth is about 4.5mm IIRC. Add to that the thickness
of a plastic washer and a 4~5mm screw length should work.
Appropriate screws are available as a service item for cell
phone, etc.. repair (try Evilbay). Washers are easier to
make than find and can be cut out of plastic stock with a paper
punch.


#16

Have you modified your 12C+ as you describe, replacing the heat stakes with screws? If so, did you have any problem with cracked cores?


#17

Quote:
Have you modified your 12C+ as you describe, replacing the heat stakes with screws? If so, did you have any problem with cracked cores?

Not yet as I'm still waiting on the M1.2 screws. I thought
to grind a parallel slot partially through the threads of a
single screw and use it as a poor-man's tap to thread each stake
in advance. Although I suspect that is overkill.

Concerning the potential to crack a stake, I'd actually thought
to slice through the stakes with a very thin kerf saw such
that the screw when driven would freely expand the stake until
it wedged in the pcb hole. That as well seems excessive.

M1.2 is almost a little undersize and I'm wondering if there will
be sufficient mating wall depth to thread. M1.3 is probably ideal
but there isn't much of an economical choice with this microscopic
hardware.

If there is general interest I'd be happy to report the results.


#18

Maybe heating the screw is an option?


#19

Quote:
Maybe heating the screw is an option?

Mounting a jeweler's cross bit in a temperature controlled iron
had crossed my mind. However I've had mixed results in the
past trying to so. Eg, controlling both iron temperature and
heat transfer to the screw such that the plastic isn't overheated.
In this case the stakes are a low, fairly isolated mass and if
they should overheat and distort it could make for a really bad
day. The other potential is to have the ABS reflow so well it
seizes the screw in the stake with similar consequences.

Although one scenario where this may be worth a shot would be if
the screw threads should strip out of the stake from repeated
insertions/withdraw cycles. Touching an iron to the head of
the screw in cautious doses can reflow the sheared ABS sufficiently
to reestablish functional threads. This may be useful in my case
as I'm concerned M1.2 diameter may be undersize.

#20

Quote:
Have you modified your 12C+ as you describe, replacing the heat stakes with screws? If so, did you have any problem with cracked cores?

I came across some jpegs I took a while back of 12c+ internals.
Unsure whether others here have already done so but on the
chance they may be useful to someone I've located them
here.

No 15c le pictures yet but the current lqfp package makes
a compelling case for pcb trace out and capture of the
schematic. I don't expect anything surprising as it appears
to be functionally identical to the 12c+ which AFAICT is
largely the Atmel reference design. However it
would be a useful reference for a plethora of lost time
projects. Maybe after the "limited" marketing campaign is
over and the "recoup the NRE" phase begins I'll pick up
a second 15c le from my local MalWart.

#21

Quote:
BTW, has anyone got photos of a disassembled 2xCR2032 HP-12C showing the actual keyboard construction/design. had a bit of a look with google, found various comments from 'experts' but no actual photos.

I just uploaded some -- see above post in this thread.

Note the choice of legged snap dome was functional as the
dome-side pcb routing takes advantage of this. So if you'd
like to get the tactile feel of a legacy voyager you could
cover the center contact trace exit with a strip of kapton tape
and substitute a full circular dome. The original voyager
domes are 9mm with a 150~170g actuation force. I forget
what I'd measured the 4 legged domes on the 12c+ (and presumably
15c le) to be, but I'll recheck.

Added:

The 4 legged domes in the 12c specimen I have at hand are
8.36mm in diameter with an approximate 220g inflection force.
Assuming this is representative of average production, the force
needed to actuate a 12c dome is substantially greater than legacy
voyager counterparts. Cut/legged domes also have a sharper
transition compared to the full domes of the same diameter,
which is likely the cause of the tactile difference.


Edited: 4 Oct 2011, 11:25 a.m.


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