HP 42s Bad Key - Advice Requested

[BillBee]

Greetings HP Gurus!

I have a 42s which can only be started after I short the terminals - later it can be shut down normally (shift +on). It is fully functional with the exception of the "6" key. I do not believe it is the ribbon connection as every other key works and pushing under the display does not lead to function in the non-working key. Key press is a dream throughout with no evidence of previous owner spills evident.

With my 32s, and a 48, which had the keyboard ribbon cable issue, they never had just one key bad (with the exception of the "on" key if memory serves). Pushing under the display usually confirmed the issue. Going through the older posts I did not find a specific reference to just one key going bad.

My instinct is to open the case and treat the key's access hole with DeOxit and a piece of wire. But I hate opening Pioneers and this one is exceptionally clean.

Question: Is there any insight into what I could try to restore the bad key in lieu of surgery?

Thank-you for any advice!
Bill

[Pjwum]

Hi Bill!

I recommend to not open the case. Also please do not use any wires to clean something up. Eventually you will ruin the conductor foil underneath the keyboard. I agree that if there is an issue with solely one key (except ON), the foam pad might not be the primary cause.

Remove the batteries. Bath and clean your device with the lower three key rows in IPA and press the bad key multiple times. An utrasonic cleaner will help. Let it dry in warm conditions a week or so. If you are lucky, the key issue and the problem during start-up could be interrelated.

If the keyboard operates normally again and you still need to re-insert batteries before start-up then you might open the case and try to resolder the CMOS-RAM.

Does it keep memory when you take out the button cells? Are your batteries fresh?

Please post your results!

Patrick

[BillBee]

(04-29-2021 11:01 AM)Pjwum Wrote:  Hi Bill!

I recommend to not open the case. Also please do not use any wires to clean something up. Eventually you will ruin the conductor foil underneath the keyboard. I agree that if there is an issue with solely one key (except ON), the foam pad might not be the primary cause.

Remove the batteries. Bath and clean your device with the lower three key rows in IPA and press the bad key multiple times. An utrasonic cleaner will help. Let it dry in warm conditions a week or so. If you are lucky, the key issue and the problem during start-up could be interrelated.

If the keyboard operates normally again and you still need to re-insert batteries before start-up then you might open the case and try to resolder the CMOS-RAM.

Does it keep memory when you take out the button cells? Are your batteries fresh?

Please post your results!

Patrick

Good Morning Patrick,

Thank you for the advice and I will heed it.

Memory remains and the cells are fresh.

Thank-you again,
Bill

[Pjwum]

Owner tried to clean underneath the keyboard, or open the case, don't know. The result makes me cry.

[BillBee]

Yikes.

[franz.b]

my 27s was not in this condition but I fixed it with a conductive ink pen.

[BillBee]

Thanks Franz,

I will keep that option in mind if a trace is bad.

-B

[Terje Vallestad]

(04-29-2021 04:56 PM)Pjwum Wrote:  Owner tried to clean underneath the keyboard, or open the case, don't know. The result makes me cry.

You can probably replace it with a keyboard foil from an 17BII that are cheap as chips on the ‘Bay

Cheers, Terje

[ijabbott]

(04-30-2021 07:27 PM)Terje Vallestad Wrote:  

(04-29-2021 04:56 PM)Pjwum Wrote:  Owner tried to clean underneath the keyboard, or open the case, don't know. The result makes me cry.

You can probably replace it with a keyboard foil from an 17BII that are cheap as chips on the ‘Bay

Or one of the other Pioneers, such as HP-10B.

[Pjwum]

I tried to fix the broken traces with conductive ink but it turned out as not reliable. When I spot a cheap 10b/17bii I will get it and transplant the contact foil. (But only from an already broken sample. Every working HP deserves to live on.)

[BillBee]

Thank-you guys for the advice.

I will try the ultrasonic cleaning first prior to any disassembly.

On this page:

https://www.keesvandersanden.nl/calculat...repair.php

(Thanks Kees! btw) I got quite an education on the keyboard assemblies.

Not quite as simple as the Voyager and 41 key cleanings.

Thanks again!
Bill