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.