Reviving your old HP48 (dead pixels or dead key? here's a possible fix)
- From: "Han" <rs1n@xxxxxxxxxxx>
- Date: 21 Nov 2005 18:33:29 -0800
I've noticed quite a few eBay sales for HP48SX calculators with dead ON
keys or deal pixel columns. Many of them were SX models. If you are
willing to take some risks, you could possibly restore your HP48.
First, I believe that many of these problems are due to overusing the
card slots. Meaning, if you were swapping cards in and out every other
day, it could eventually push the PCB out of alignment with the
connectors that handle the LCD and keyboard input. The card connectors
are mounted onto the PCB, which are then held in place by twist-tabs (6
of them) which are resonsible for pressing the PCB against the top
section of the HP. There are connectors on the PCB which are
responsible for keyboard input, and LCD display. Over the years, either
through dust collection or perterbation of the PCB, or a combination of
both, the LCD/keyboard connectors move out of alignment or simply no
longer make contact. You can diagnose this by trying the following:
For missing pixels, try pressing on the bezel just below the LCD (and
above the menu keys) or the bezel near the top. Do the pixels reappear?
If so, your PCB simply needs some cleaning.
For dead keys, press on the bezel between the LCD and the menu keys.
Does your dead key respond? If so, there is a gap between the keyboard
connectors and the PCB.
Both of these problems are fixable if you are careful and meticulous. I
put together a mini-howto here:
http://www.math.uiuc.edu/~handuong/files/hprepair.zip
In it is a text file with many photos (4MB zip file).
My results have been fairly good; though I did make one big mistake
after further fiddling. I received an HP48SX that showed only 3 lines
of pixels! Plus most of the keys were not responding. The previous
owner tried to repair it, but I suppose that person did not quite know
exactly what to do. So, I managed to fix it so that the LCD displays
every single pixel. I also managed to get all the keys to respond.
Then, I tested out the card slots... and that's when the [L-SHIFT] [4]
[5] [6] [X] row on my keyboard decided to not respond unless I pressed
down on the bezel. It was then that I realized that the force from the
card connector was nudging the PCB off its good spot. So I tried to
tinker with it some more and managed to break a twist-tab ! =(
Overall, the repairs I did work, but I was wreckless the first 5 times
and in the end the twist-tab was twisted one too many times. The
calculator still works if I press down on the bezel... Looks like I
just need to find a new way of fastening the PCB (only one twist-tab
got broken). Again, so long as your methodical and careful, you will
probably make your fixes in one or at most two tries.
Han
.
- Follow-Ups:
- Prev by Date: Re: What's the best way to learn how to optimize ASM?
- Next by Date: Re: The Qonos Scientific PDA
- Previous by thread: MOD operation on integers?
- Next by thread: Re: Reviving your old HP48 (dead pixels or dead key? here's a possible fix)
- Index(es):
Relevant Pages
|
