HP-42S faulty keys



#18

I have three of these machines and two have the same problem. Of the right most column of keys on the keyboard the bottom six do not work at all. Only the XEQ works in this column and it takes a bit of extra pressure to make it work. The +, -, X, /, <, and TAN keys are completely dead.

Is there something common that can cause these keys and only these keys to fail?

I've owned and used 42S's extensively since they were introduced and I sure would like to fix the two that don't work. I've never seen this (or any other key problems) with any of the 42's I've used over the years.

Any help or idead much appreciated. I'm not beyond taking them apart if that's necessary but of course would rather not.

Best, wes


#19

I am sorry to say that once these keyboards fail, they are really dead. The contact domes are made of plastic; once they lose their 'spring' they are dead forever.
Though, it is possible to rebuild the keyboard, it is highly dependent on voodoo, requires great dedication (and JB Weld), and you will need a working keypad dome sheet.

Again, sorry for your loss; toss it in a box in case you need an LCD or a main board for the replacement you will most likely get...because the 42s is just that good. (Just avoid buying fromthat ebay guy.)

Edited: 23 Apr 2009, 11:38 a.m.


#20

Could the keyboard from another Pioneer, such as an HP 32Sii be used for this? I'm just asking, because I've never opened one of these, but have done so with the Spice series.

Finding a working HP 42s for less than a fortune is quite difficult these days. I'm sticking with my Free42.


#21

It is possible to replace the keyboard sandwich with another Pioneer series, but it is very, very intense.

See the 4th posting on

http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv018.cgi?read=138580#138580

Edit: fixed link


Edited: 23 Apr 2009, 12:18 p.m.


#22

Quote:
It is possible to replace the keyboard sandwich with another Pioneer series, but it is very, very intense.

Which series will work? Or any of them?

Quote:
See the 4th posting on

http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv018.cgi?read=138580#138580


Interesting stuff...some folk do things that simply amaze me at times.

Best, wes

#23

Quote:
Could the keyboard from another Pioneer, such as an HP 32Sii be used for this?

I can't say because I've never used a 32Sii at all. It's not like the keys are worn out really, the problem appeared on all the keys affected at the same time. And on the one machine, it's been in storage for a couple of years and was working fine when it was put away. Now, no-go on just those six keys along the right side of the board.

Quote:
Finding a working HP 42s for less than a fortune is quite difficult these days. I'm sticking with my Free42.

I've noticed that. Last one I followed on eBay went for well over $150. At least I have one that still works and the 48GX and even an old 25C that still lights up.

Thanks for the thoughts.

Best, wes

#24

Quote:
Finding a working HP 42s for less than a fortune is quite difficult these days. I'm sticking with my Free42.

Well, not quite. It's true they were going for $400 +/- a few months ago. I recently picked one up for $150 on eBay. Mint USA version, but w/o manual. Got one of those for $7.
#25

Quote:
I am sorry to say that once these keyboards fail, they are really dead. The contact domes are made of plastic; once they lose their 'spring' they are dead forever.

No loss of spring to the keys...they feel the same as always and the same as the others that do work. On both these machines the failure seems to have been fairly sudden and all the affected keys at once. It's not like they are worn out because neither have been used except very causally for about 7 years now. The hard thing is keeping working batteries in them so they work on the occasions I do pick one up. No corrosion issues either...

It's pretty much a mystery to me.


#26

Hi.

look at this picture...

it is a 20S with 32SII hardware.

http://img25.imageshack.us/img25/6825/18012008134s.jpg

regards,

nacho





Edited: 24 Apr 2009, 10:21 a.m.

#27

It seems to me that this is may be just a problem with the connectors. I read somewhere on this site that a relatively easy way to fix the problem of a row or column not responding is to tighten the 6 twisted tabs holding the circuit board in place. Of course, you have to open the calculator to do this. I have had some success doing this with a 32-SII in the past.

I'd try this simpler solution first. Good luck.

#28

i worked on a 42s for a friend a while back, and as i recall the contact between the keyboard matrix and the 'motherboard' is purely by pressure, through a dozen or so contacts in a row. i'd guess that the failure is here, and that cleaning may well fix the problem.

to dismantle, the best method i've found is to drill out the 4 (?) plastic rivets in the battery compartment area, and through the back of the calculator to disconnect the 4 (?) at the bottom edge - after some careful measuring to work out where you want to drill.

once the back is off, you can easily remove the motherboard and clean the connections between it and the keyboard, before reassembling it back into place. the only repair work then required will be reattaching the back. oh, and while it's apart, you could upgrade the ram from 8k to 32k.

cheers,
rob :-)


#29

Quote:

once the back is off, you can easily remove the motherboard and clean the connections between it and the keyboard, before reassembling it back into place. the only repair work then required will be reattaching the back. oh, and while it's apart, you could upgrade the ram from 8k to 32k.

cheers,
rob :-)


Thanks Rob, that sounds like something I can handle and it seems worth a try. I have the face plate off one of them already.

I seem to recall reading elsewhere on this site about dunking one in distilled water for a time and then slowly and thoroughly drying it out. Anyone here tried that approach and have any luck/failures or?

Best, wes


#30

Hi, wesjones

I've ever repaired two 32sII with faulty contact of the keypad.
It may be possible to repaire the 42s if the deformed foam rubber is the cause.

Repairing 32sII:
http://www.finetune.jp/~lyuka/interests/calc/hp32sII/

How to open the hp-42s:
http://www.finetune.jp/~lyuka/interests/calc/hp42s/

Regards, Lyuka


#31

Quote:
Hi, wesjones

I've ever repaired two 32sII with faulty contact of the keypad.
It may be possible to repaire the 42s if the deformed foam rubber is the cause.

Regards, Lyuka


Hi Lyuka. I read here and there in the forum before posting my question and I think I looked at both of those pages. Nice work and thanks for posting them for everyone.

What I think I'll do eventually is take the one apart and at least check the foam pad and the contacts there. Then play it by ear if that's not the problem.

Best, wes

#32

great photos!!

how did you handle the 4 lower heat stakes? my solution was drilling from the back of the calculator, then repairing the damage to the back of the housing - were you able to just prise them apart?

i'd be very reluctant to remove the front plate unless it was absolutely necessary!

cheers,
rob :-)


#33

Hi.

I've ever opened three 32sII and two 42s successfully by untightening the four lower heat stakes as follows.

After drilling off the upper four heat stakes,
warm the back of the calculator and the metal back plate of the key pad, very tenderly to some 50 degrees centigrade (120'F), by using hair drier.

This level of the temperature won't damage the calculator (however the LCD should better be isolated) but is enough to soften and deform the brim of the lower heat stakes rather easily, to get the housing apart.

Then using no tools but with your own hands, grab the case stiffly and open it very slowly and carefully.

Good luck.

#34

(Sorry about lack of response; I've been away from electricity for a bit).

Since all the keys seem to click just fine, I agree with the others that this may be a debris or keyboard/mainboard contact issue.

I would defer to Lyuka on the repair strategy. (Lyuka, great pages, by the way.)


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