Recovering non-responsive buttons on 42S

[mats]

This is probably a naive and common question so I apologize in advance for my first post on this forum. Is there simple way to revive "non-working" HP calculator buttons using spray-on contact cleaner without taking the calculator apart?

I have an old 42S on which the "On" (EXIT) key stopped working along with the entire right side +, -, X, / and < keys. Figuring I had nothing to lose I sprayed the whole keyboard with CRC QD Contact Cleaner - basically soaked it. This more or less succeeded and I was very happy for about half an hour - but then the keys stopped working again.

Is there any possible merit to this approach? Has anyone else tried this or any other type of solvent? It seems tantalizingly simple and almost works, but of course almost isn't good enough.

[GreyUser]

It is the most common problem on that series of machines, The foam pressure pad that holds the keyboard connection against the processor board has lost its spring force and lost contact. The foam degrades over time, becomes gooey and looses its ability to maintain the force required. The unit needs to be opened, the board popped off and the pad replaced and then reassembled.

Spaying solvents into/onto the unit is not a good idea, it can attack the plastic of the keyboard and do some irreparable damage to the small pieces of ABS that hold the keys in place. Once they break, it is game over.

The repair is documented here on this website/forum many times.

[BillBee]

Hi There,

There is a guy here who has offered to repair them. TBH I can't remember his user name but someone here will - not a bad option to consider.

I have popped a known broken 32sII apart and while daunting it is possible without damaging the unit - but its the reassembly as one needs a nice crisp closure. That said a 32s is not the same value of a 42s. There is a youtube documenting the procedure on a 32s which is the same build as the 42.

-Bill

[mats]

Thanks very much to GrayUser and BillBee for the ideas. I searched the forum for "42s repair" and got lots of results (I had previously tried searching for "repair 42s" and found nothing which is when I posted my own question - I should have known better .

Like most of you I have had many HP calculators over the years. I had a 15C (made in the US) for 25 years before I lost it - it never had a problem and it was used a lot and I loved it. I think I paid about $100 for it in 1984 which was a lot for a graduate student. I recently found an almost identical 15C (1988) on eBay for $200 and bought it, and it made me so happy that I decided to try to revive my old 42s (1987) and 48G (1993), both made in Singapore, that died many years ago. Hence the question I posted.

Just to add some data-points to the posts I have read about the longevity of other models, I have three 35s calculators and I love them (in principle) but in practice all but one developed keyboard problems after about a year of light use. The one that survives was made in the Philippines, and the two crippled ones were made in China. I also bought a 49G some years ago, perhaps out of fondness for my old 48G. As far as I know it still works fine but just don't like using it so its basically brand new.

[BillBee]

https://www.hpmuseum.org/cgi-sys/cgiwrap...read=15885

https://www.hpmuseum.org/cgi-sys/cgiwrap...ead=150148

These should give you a good place to start.

I love the wealth of info here and the old forums.

BTW if you love the 15c the SwissMicros DM15 is awesome.
Bill

[GreyUser]

This is where all Pioneer repair adventures should begin:

https://www.hpmuseum.org/cgi-sys/cgiwrap...cgi?read=5

[BillBee]

Another good link:

https://www.youtube.com/watch?v=G8wS95wK4bI

I don't know if Logan is a member here but I have watched a lot of his great vids.

-B

[GreyUser]

(10-01-2020 11:14 AM)BillBee Wrote:  Another good link:

https://www.youtube.com/watch?v=G8wS95wK4bI

I don't know if Logan is a member here but I have watched a lot of his great vids.

-B

IMO A rather poor opening method. Use the common method of reducing the heat stakes with a twist drill. You will absolutely bugger up the case and probably bend the crap out of the aluminum bezel with the method in that video.

Next issue is choice of foam pad replacement material. Worst choice ever. That 3M double sided tape is acrylic foam which has horrible compression memory, the exact opposite of what you want which is either a polyurethane or silicone rubber based material.

As for removing the logic board, you really should use a pair of duck bill pliers. Anything else just makes the job unnecessarily more difficult.

Yah, okay, it’s on 20S, no huge loss. But a 42S? Please don’t abuse a 42S like that, is it totally unnecessary.

[BillBee]

(10-02-2020 02:00 AM)GreyUser Wrote:  

(10-01-2020 11:14 AM)BillBee Wrote:  Another good link:

https://www.youtube.com/watch?v=G8wS95wK4bI

I don't know if Logan is a member here but I have watched a lot of his great vids.

-B

IMO A rather poor opening method. Use the common method of reducing the heat stakes with a twist drill. You will absolutely bugger up the case and probably bend the crap out of the aluminum bezel with the method in that video.

Next issue is choice of foam pad replacement material. Worst choice ever. That 3M double sided tape is acrylic foam which has horrible compression memory, the exact opposite of what you want which is either a polyurethane or silicone rubber based material.

As for removing the logic board, you really should use a pair of duck bill pliers. Anything else just makes the job unnecessarily more difficult.

Yah, okay, it’s on 20S, no huge loss. But a 42S? Please don’t abuse a 42S like that, is it totally unnecessary.

Hi GU,

For my 32S I used a drill bit to "thin out" the upper rivets and was able to pop those easily - no plate distortion. The lower 6 (4?) were forced with out case damage too. But for reassembly the top of the bottom rivets had to trimmed a bit to fit back into the upper half receiving holes. Mind you the calc was processor dead from corrosion so it was for a learning experience.

I must admit the method of using heat to peal back the face plate to gain access to the top of the lower studs was considered versus the "brute force" method. I might pick up another dead one and try that.

What type of foam strip do you recommend?

I have repaired a 48 and replacement of the foam is the best. Shimming works for a very small period.

Thanks for sharing your experience,
Bill

[ramack]

Thanks for posting this info. My 42S that I purchase while in college, stopped working (all right most buttons) this week. This thread and a few videos help get it working. The issue was the zebra cable / grey foam. I replaced the foam with craft foam from Michaels. I used to layers of 1/16 thick adhesive to build up to 1/8.

I'm probably going to use screws to reattach the mounts that I drilled out near the batteries. I don't want to glue them and do want to reattach those points. Just need to find small enough screws for plastic/wood.