HP 48sx - Keyboard Replacement and LCD Upgrade

[Sanjeev Visvanatha]

My trusty 48sx was my first HP, and was bought for me in Jan 1991 before I was entering Engineering school. When the calculator was still a teenager (c. 2009 or so), it suffered an issue with the keyboard foam deteriorating, causing keystrokes to miss. At the same time, one of the ENTER key's hinges physically broke.

My very first repair job started at that time, and I entered the calculator using some instructions I found here (the toenail clipper method). The repair was sort of successful, and I had a few dropped LCD lines, but the keys all responded. Sadly, the lack of a quality repair left this unit to sit on the shelf. I purchased several other HP units from then till now, effecting repairs on several Pioneers. I always hoped I could salvage and repair this unit someday.

Fast forward to 2019, armed with some repairs under my belt, I attempted another shot at repairing this unit. To repair and upgrade the 48sx, I purchased a 48S with the foam issue, but otherwise excellent condition to use as a keyboard donor and a working 39G for its black LCD. These two donors would resurrect my own 48sx. Since I wanted the unit to look as original as possible, I elected to use the original 48sx metal overlay/bezel instead of the one that came with the 48s.

I will be putting a PDF file together with some photos, but here is a teaser.

[grsbanks]

Nice job

[mfleming]

I'd be interested in hearing about your approach to removing the keyboard plate. After reading Geoff Quickfall's description of the process, I tried to do that with a Pioneer calculator but made a mess of the plate!

~Mark

[EugeneNine]

I used a cottonball to dab IPA on mine and let it sit overnight until the adhesive dissolved then it came right off

here is my thread https://www.hpmuseum.org/forum/thread-11652.html

[Sanjeev Visvanatha]

(04-14-2019 03:04 PM)mfleming Wrote:  I'd be interested in hearing about your approach to removing the keyboard plate. After reading Geoff Quickfall's description of the process, I tried to do that with a Pioneer calculator but made a mess of the plate!

~Mark

I used a flat plastic spatula-like tool from the bottom of the keyboard. Geoff uses a pocket knife I believe. I will have a photo of this.

[Sanjeev Visvanatha]

Here are some photos and description of the process I used. I compiled it mainly for my own reference.

HP 48sx Rebuild.pdf

[Jonathan Busby]

(04-15-2019 02:35 AM)Sanjeev Visvanatha Wrote:  Here are some photos and description of the process I used. I compiled it mainly for my own reference.

HP 48sx Rebuild.pdf

Thanks so much for the link and the effort you put into documenting your repair!

I soon plan on hardware hacking an HP48 and your experiences definitely help

Regards,

Jonathan

[mfleming]

Sanjeev,

You should definitely add this to the Articles forum with an introductory description and maybe a small photo for illustration. I don't think I've ever seen a keyboard replacement walkthrough, so that's a new contribution to the body of knowledge. This is a great reference next time someone needs to do the same work!

~Mark

[zx_spectrum]

(04-14-2019 03:05 AM)Sanjeev Visvanatha Wrote:  I will be putting a PDF file together with some photos,

cannot wait for that PDF

[rprosperi]

(04-17-2019 05:00 AM)zx_spectrum Wrote:  

(04-14-2019 03:05 AM)Sanjeev Visvanatha Wrote:  I will be putting a PDF file together with some photos,

cannot wait for that PDF

A link for the PDF is available in post #6 above.

[Jonathan Busby]

(04-17-2019 01:17 AM)mfleming Wrote:  Sanjeev,

You should definitely add this to the Articles forum with an introductory description and maybe a small photo for illustration. I don't think I've ever seen a keyboard replacement walkthrough, so that's a new contribution to the body of knowledge. This is a great reference next time someone needs to do the same work!

~Mark

Seconded

Regards,

Jonathan

[Sanjeev Visvanatha]

(04-17-2019 02:39 PM)Jonathan Busby Wrote:  

(04-17-2019 01:17 AM)mfleming Wrote:  Sanjeev,

You should definitely add this to the Articles forum with an introductory description and maybe a small photo for illustration. I don't think I've ever seen a keyboard replacement walkthrough, so that's a new contribution to the body of knowledge. This is a great reference next time someone needs to do the same work!

~Mark

Seconded

Regards,

Jonathan

I’ll have a look at the articles section and see how I could contribute this there. Thanks for the positive feedback !