Hp 48G+

A few days ago days ago I had the need to use my old HP 48G+ after ages of inactivity. The RPN notation is so handy and I have some old application that I still use.


A source of software (games, spreadsheets, MatrixWriters …) and information about the  HP 50, HP 49, HP 48  and other programmable graphic calculators is http://www.hpcalc.org/

Btw today when I turned on my old HP 48G+ … no damn! again! : the keyboard was not working.

1995 my first HP :  HP 48G1999 replaced due to  keyboard dead
my second HP :HP 48G+ … 2011 dead of keyboard
(keyboard seems to be the weak point of HP) 

Because a my old university deskmate (Simone) has an HP 48sx with broken display we are thinking to transplant the display from my 48G+ to his 48Sx.

Replace screen of HP 48Sx

The HP 48sx (class 1989)   has display with some dark spots. Those spots seem to be caused by corrosion of LCD liquid (but really I’m not sure). 


Here the complete instructions how to proceed in order to open HP (instead, here in my post, I report steps quickly): http://www.hpcalc.org/details.php?id=3430


I used a tools that I bought some years ago in order to change the iPod battery.
As I said I started following instruction reported here  where as opener tool is specified a toenail clipper. Really “toenail clipper” is very useful to open HP … more than  iPod tool which I used.

starting from front of calc (where is placed the display)


continue on both sides of HP


here the final result (btw we have to open bottom side yet)


at the end I continued with bottom of HTP (where is placed the battery compartment).

About this point original tutorial reports :
 First, unhook the positive battery terminal from the battery compartment. 

Remove battery flap first
Remove battery flap first

You have to be careful about this step since you risk to break the battery terminal and/or mainboard : you have to unlock metal positive terminal  in order to allow  its shift out from battery compartment when you’ll remove  the back  part of calculator. I’m sorry … I have to censure some images due to crudity and violence on my HP. Open the bottom of calc it is quite tricky (however complete steps above link).4Now that I completely opened my HP I need to remove the mainboard in order to get access to keyboard connector! To remove mainboard we have to rotate several little metal strips in order to allow passage of them into little slots.


Those strips are delicate so you have to use small pliers … and not as I did  following tool:

In fact I have broken some of those metal strips so I’m not able to remount stably the mainboard. I was obligated to drop the idea to repair my HP. So my story finish here but start the story related to other HP with broken display.

Now Since my display is perfectly working we have tried a display “migration“.
From my
Hp-48G+ (1999) To Hp-48Sx (1989)
10 years older

Initially I was not sure about this operation since LCD connectors are quite small and the conductive “rubber” seems to be quite tricky to place. Moreover display has to be  separated by metal frame (however it is stuck to frame  with adhesive).IMG_4322 copy

After some handling now the HP 48sx has a new (perfectly working) display!

HP 48SX Replaced display
HP 48SX Replaced display
HP 48SX Made in Italy
HP 48SX Made in USA

Just last note : Hp48Sx is made in USA! (?) 1989!!!

that’s all

1 Comment

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  • Dear Busylog.
    Do you have some experience on HP48 battery drainage? Some users state that, when the batteries are placed backwards, some Zener diode (or diodes) get burned and become resistive…do you have some experience with this one?
    Sincerely yous.
    K. Adam.