-*-text-*-
Hello fellow HP48 owners :-)
If you have a 48S/G, you may have thought about expanding your
memory. If you refrained because you didn't want to uglify your
calculator, now you have no excuse. I bought two 48S's from EduCalc,
and disassembled the first one according to Paul Smith's article
(thanks for your bravery, Paul:-) I managed to get it back together,
using epoxy to secure the faceplate down with a minimum of wrinkling.
My first new 288K calc is quite usable, but looks like an old battle
implement (at least a little beat up :-). It's safe to say that a
calculator disassembled this way will never be the same again.
I wanted calc#2 to be prettier. It turns out that it's
relatively easy to make cuts in places not normally visible (behind
the red IR port lens & in the battery compartment) to render the front
and back halves separable. The benefits of this approach are that
your 48 still looks like new, and the structural columns can be
salvaged to retain the solid "HP" feel of the new calc.
I've written up the directions below. I've also included Paul Smith's
disassembly note at the end, for reference.
Disclaimer: The directions are based on MY 2 HP48S's, and may not
apply to any others in the world. I'm providing this info so that
someone (maybe you) may benefit from it. I can't be responsible for
any damage you inflict on anything (including yourself) by following
these directions. I also can't guarantee the accuracy of my
descriptions. Please THINK about what you're doing to make sure it's
not obviously insane (loosening the LCD with a hammer, etc.) You will
void your warranty if you take apart the calculator.
Disclaimer softener: This worked for me :-) If you follow directions,
you and your 48 should be OK. Also, this is a very long post
describing a very simple procedure. Don't be discouraged by the
length. The detail is there to help prevent you from goofing :-)
Good luck, and enjoy!
David.
--
David Fenyes dave@image6.uth.tmc.edu
University of Texas Medical School Houston, Texas
-------------
Tools & Materials
Feel free to improvise. I used:
1) an X-acto knife, preferably with a #6 blade (thin, narrow trapezoidal
blade with a shallow angle -->
____________________
______ / <- sharp!
(______) ________/
_________/
The blade should fit nicely in those keyboard template slots at the
ON, ENTER, MTH, NXT, <-, and + keys.
2) A broad, blunt, thin blade, such as the screwdriver on a
Victorinox-brand swiss army knife. A butterknife may work. Using a
narrow, thick screwdriver will leave ugly marks in the soft plastic.
3) A drill with a very small bit, or a 1/4" bit.
4) The slick backing paper from a sticker
5) a couple of butter knives, Q-tip stems, or wooden matchsticks.
6) Some 14 Ga solid copper wire (I used laquered magnet wire).
Directions:
Top - toward the IR lens/serial port connector.
Bottom - toward the "ON 0 . SPC +" row of keys
Back - toward the battery-compartment side of the calc.
Front - the faceplate side of the calc.
Overview:
=========
Instead of ripping off the tin faceplate and destroying the rivet
heads, you will make well placed incisions behind the IR lens and in
the battery compartment to defeat the 10 plastic rivets. The
abbreviated plan is:
1) empty battery compartment and remove IR lens.
2) make 2 holes in the recess behind the IR lens in order
to gain access to the 4 rivets above the display, and slice through
them.
3) Enlarge the hole behind the (+) battery terminal, and slice the
exposed plastic rivet. Make a corresponding hole and slice the
corresponding rivet on the right side of the compartment.
4) Dig out the bases of the remaining four rivets beneath
the bottom battery-separator ridge in the compartment.
5) Separate the two halves of the calculator.
6) "repair" the plastic rivets to restore structural integrity.
Detailed Instructions:
======================
0) back up your memory and turn the calculator off.
1) Remove the battery case cover and batteries. Carefully peel off
the foam pads/battery connectors from the battery compartment and stick
them on the piece of sticker backing.
2) Remove the dark red plastic IR port cover:
- Turn the calc back facing you, wedge the dull blade between the IR
lens and the calc body about 1cm from the left edge and pry the lens
off. Repeat for the right side. The lens will pop out unharmed. (Or
you can use your fingernails to pull the lens off for minimal risk of
blemishes)
3) Begin the "plastic surgery":
- Look into the recess behind the IR lens:
______________________________________________________
| |
|______________________________________________ |
#1--------> |----- |. . . .| / /\ /\ \ ----- | <-------#2
| | \_______/ / \/ \/ \ | |
|______----------------------------------------______|
\ /
\ /
\_______________________________________________/
I have drawn the IR and serial ports, and the two slots you will need
to make. Look into the serial connector and note the level of the
PCB. Using the X-acto knife, make a 1cm horizontal score (#1) about
halfway between the level of the serial pins and the PCB.
Use a drill with a very small bit (~1mm) to make a row of holes
along the scored line. *REMEMBER* where the PCB is, and be sure to
angle the drill very slightly downward. If you do this, you will be
drilling into air, and will not harm anything of consequence inside
the case. Using the X-acto blade, connect the holes to make a slot.
If you can't see very well inside the slot, have faith. Stick the
X-acto blade into the slot, angled slightly down (away from the PCB),
and slice anything you encounter. You should be able to move the
blade freely in the slot. To a casual observer, you will look as if
you are lobotomizing your calculator. In fact your blade will only
hit the 2 plastic rivet bodies behind the slot (and air).
Repeat the procedure to make a symmetrical slot on the other side
(position #2) next to the IR port. make it the same width and level
as the first slot. Again, you will be drilling and slicing into air
if you keep the angle slightly down.
** Alternative: Your task may be considerably simpler if instead of
making slots, you use a 1/4" bit to drill holes slightly below the
slots indicated above (angled downward, of course,) to give yourself a
good view of the rivets before you cut them.
Bravo :-) You have accomplished the scariest part. You should now
be able to pry the top of the calculator apart very slightly.
4) Slice the two rivets at the top edge of the battery compartment:
Use the following schematic for the next two sections. Remember, it's
ASCII art, so don't measure it with a ruler :-). Read the text for
specifics:
Battery Compartment
X TOP X
****-----------------------------****
#### |
#### | top section
ridge 1 -> ------------------------------------+
| |
**** **** **** **** middle section
ridge 2 -> **X*-------*X**--------**X*------*X**
| ####
| #### bottom section
+-----------------------------------+
BOTTOM (-)
X = plastic rivet
# = the hole is already there.
* = you make the hole.
Turn the calculator so its back is facing you. Bend the (+)
batery terminal (the one in the top left corner of the compartment) so
that it sticks straight up and is flat against the left side of the
compartment. This will expose a rectangular hole in the top side of
the compartment. Using the blade, slice upward along the edges of the
hole and across to extend the hole about 3-4 mm toward the rear of the
calculator.
The hole is now a window into the calc innards. Look into the
window at a shallow angle. You will see a plastic rivet. This is the
rivet amidst the "[6] [X] [9] [/]" keys. You can slice this easily with the
blade.
Now you need to make an identical window in the top right corner of
the case and slice through the second rivet (the "[Lshift] [Alpha]
[4] [7]" rivet.)
5) Free the remaining four rivets from their bases:
The battery compartment is divided into three sections by two
ridges. The four remaining rivets are behind the bottom ridge, very
slightly toward the middle section. They lie amidst the following
keys:
"[1] [ON] [0] [Rshift]"
"[1] [2] [0] [.]"
"[2] [3] [.] [SPC]"
"[3] [-] [SPC] [+]"
You will harm nothing by digging around, but you want to damage as
little of the compartment as possible. Start slicing out sections of
the bottom ridge using the keys as a guide for the horizontal dig
sites along the ridge. Actually, the "+" signs on the bottom and
middle battery icons accurately indicate the positions of the middle
two rivets. When you encounter a small (~14Ga) circular hole, you have
identified a rivet. You need to free each rivet from the surrounding
plastic so that it wobbles freely.
HINT: Since you'll be doing lots of digging, you may try to use the
edges of the battery case for leverage. If you line the externally
visible outline of the compartment with masking tape, you'll prevent
cosmetic damage.
6) Separate the two halves of the case:
Now the calculator's keyboard should be facing you. Insert the
blade in the keyboard-template slot near the NXT key. The blade
should go straight back to the back half of the calc. Apply pressure
on the handle toward the midline of the calc. This will disengage the
front half from the back half. With the screwdriver blade, gently pry
the halves apart at the [F] key. Place something (like a butterknife)
between the halves to keep them apart. Repeat the procedure at the
[MTH] key (pry near [A]), the [ENTER] key (pry near [SIN]), and the
[backspace] key (pry near [1/x]). The whole top part of the
calculator should be nicely separated.
The bottom 3 hooks are somewhat more resistant to separation,
probably because of their close proximity to one another. The best
thing to do here is insert the blunt blade (victorinox screwdriver or
butter knife) between the two halves near the [-] key. Pull the
handle up toward yourself. The bottom half should disengage from the
top half. Stick something (like the butterknife or wooden matchstick)
between the halves to keep them apart. Repeat this now at the bottom
of the calc (the "." key) The calculator should completely come apart
now.
7) Putting it back together.
You could probably just snap the two halves together. However, if
you want a little more stability, it is possible to restore the
structural function of the rivets.
The rivets are hollow. Using the X-acto blade, clean up the ends of
the rivets on both halves of the calculator. The hollow center of
each rivet should be round and free of plastic debris. You may also
wish to clean up your hacking near the IR port and in the battery
compartment.
14 Ga laquered solid wire fits snugly in the hollow rivet bodies.
Cut six straight pieces of the solid wire, exactly 1cm each. Make
sure that the ends of each piece fit neatly into both halves of the
top six plastic rivets (you won't need to restore the four bottom
rivets that you freed from their bases.) Push the wire pieces into
the top six rivet bodies in the back half of the calculator.
Bend the (+) battery terminal back into shape. Align the front half
of the calculator carefully with the back half. The rivet remnants on
the front half should align with the wire pieces sticking up from the
bottom half. The (+) and (-) battery terminals should fit through
their respective slots, and the top half should rest flat on the
bottom half. Press the calculator together starting at the bottom.
The pieces should snap together with no difficulty. If the rivets and
wire are misaligned, you may need to push the wire into alignment with
a needle.
Remove the two foam-backed battery terminals from the
sticker-backing and replace them in the compartment. Replace the
batteries and battery compartment cover. Snap the IR lens back into
place.
Congratulations! You have disassembled (and hopefully upgraded :-)
your calculator without ruining its appearance :-) If you were
careful, it should look brand-new!
Appendix:
This text is written by Paul Smith:
++++++++++++++++ start forwarded text ++++++++++++++++++
Disassembling the hp48sx
(may or may not correspond to the 48s, but probably will to some
extent)
Sufficient numbers of people (more than 1) have requested information
on how to disassemble their hp48. Despite the fact that that's pretty
scary, I will entail what I know here. Thanks to David Holmes for
taking the first step and helping make my attempt more informed.
None of the information that follows came from hp, so if what I say
starts to sound rather official, it's not.
For the few folks out there who've actually had to send their hp48
back to hp for service, you probably ended up with an entirely new
unit. I suspect the reason for this, aside from some labor cost
savings on the part of hp, is that they really aren't much fun to take
apart. You can draw your own conclusions as to why it was designed
that way.
0. Backup your memory. You will need to remove the batteries for
awhile to disassemble the unit, and you may have them out long enough
to cause memory loss (although in my case, even 2 days didn't wipe
anything out).
1. Remove the tin key overlay. The overlay is attached with double-
sided tape of some sort. A little care and patience will allow you to
remove it only slightly warped, and it is fairly easy to straighten
out later. I took a small jewelers screwdriver and started prying
near the "ON" button, and worked upward toward the screen. When you
get near the screen, try to preserve the shape of the overlay because
that portion is a bit more difficult to properly straighten later.
Once the overlay is removed, put it in a container or somewhere away
from dust. The double-sided tape should stay with the overlay (mine
did, at least) and will gather dust and stuff making it less sticky if
left out in the open. 48sx owners will need to remove the little hp
logo insert above the screen as well.
2. Defeat the 10 plastic rivets. Believe it or not, these rivets
aren't all that critical to holding the unit together, so you can be
as careful or as reckless as you want (I prefer reckless, because I
hate plastic rivets). A good way to carefully remove the rivet heads
is to use a flat head screwdriver that is the same width as the
recessed rivet hole (4mm?) and "drill" the head away by hand with the
screwdriver. The head is about 2mm deep, so stop "drilling" there to
leave the keyboard material shoulder intact for easier reconnection
later. There are 6 rivets near the number keys and four above the
screen. These rivets above the screen perform more of a holding
function than the others, and you may want to consider using some
screws and small washers to replace them when you re-assemble.
3. Separate the lower half from the upper half. The upper half of
the calculator contains almost all of the components except for the
piezo "beeper" element, and there are no interconnecting wires between
halves. The only obstacle is the snap-together "hooks" that David
Holmes refers to. These hooks are positioned near the [A], [F], [SIN],
[1/x], [ON], [+] and [.] keys (the one by the [.] key is a real
bugger!). Refer to the cutaway diagram below for details.
Key overlay here ___
\ ____________
\ | |
____________| ______ |
| _ | | <--- Upper section.
| | | | |
________________| | | |_|
| | |___
Circuit board and other | | |
components (affixed to | / | <--- Lower section.
upper section) |/__ | Has a lip which
| | | engages with metal
Metal "hook" ---> | / | | "hook" from upper
|/ | | section.
| | |
________________| | |
| |
To separate the two sections, you will need to push the lower section
out and down around the hooks. You can't do this from the outside
because the upper section hangs over the lower, so you have to go from
the inside. Luckily, the six slots in the keyboard (used by the
separate user-overlays that fit over the original overlay) near the
[MTH], [ENTER], [blushift], [NXT], [backspace] and [-], come in handy
for this. These slots are not exactly lined up with the hooks, but
are close enough. You can insert something in these holes (I used a
jewelers screwdriver, flat head) at an angle that is mostly down and
somewhat out, to a depth of about 5mm, and come in contact with the
lower section. Push the lower section out about 2mm (this will take a
bit of force), while wedging something in the outside gap to separate
and hold the sections apart while working on the other hook positions (
a wooden matchstick works). I recommend starting with the [A] or [F]
positions first, working down whichever side you started with, then do
the other side, and leave the [.] position for later (there is no
helpful slot there).
4. Remove the battery cover and the batteries. The two battery
contacts which come through the case will need to go back through the
case when the sections separate. The upper contact is hooked on a
plastic boss, and needs to be freed from it. Just pop it off with
your finger or a screwdriver.
5. Very carefully pull the two sections apart at the top (above the
screen). If you have freed all the hooks, the case should sort of
hinge at the bottom edge. This is due to the last hook (near the [.]
key). Some careful twisting and working of the sections should free
this hook as well. You should now be able to completely separate the
two sections. I recommend at this point that you take a pair of
pliers and flatten that last hook so that it will not hold next time.
It is really not needed anyway, as the other six hooks hold the unit
together just fine.
Now you can poke around and explore things. Be careful what you
touch, I'm not sure how sensitive the insides are to static discharge
from your fingers, etc. If you're interested in adding stuff, some
open real estate can be found in the areas between the battery
compartment and the card receivers, and in the cavities in the lower
section below the tin shielding on either side of the card ports (this
is where I put some jacks). If you own a 48s, you may find a lot more
space.
If you want to disassemble the unit further, like removing the circuit
board from the upper section, you have a considerably tougher job on
your hands, and you're on your own. Also, if you separate the screen
from it's circuit board, you will disturb the rubber conductors (there
are two) which provide electrical connection to the lcd rows and
columns (zebra strips). Upon reassembly of the screen, you may find
that you have lost some rows or columns in the display (not permanent,
just a zebra strip alignment problem) and will have to keep
reassembling and perhaps cleaning until it comes out okay. I haven't
done this to my hp (yet) but I have done it to other cheap calculators
and it wasn't fun.
As to questions about what exactly is inside, I can only guess. David
Holmes had some observations, and there are apparently a lot of people
out there in netland that know a lot more about the insides already.
Reassembly-
Putting it back together is much easier. You may need to clean up the
remains of the rivet heads so they will easily reinsert into their
holes. Make sure the battery connections align with their respective
holes, and snap the unit together, applying pressure where the six (or
seven, if you left that one near the [.] key alone) hooks are. You
will probably want to hold the case together at the top with one or
two of the rivets there. If you can find a wood screw with a flat or
thin head, you can screw it into the body of the rivet and let the
head hold the upper section surface. You may need a small washer for
this. A machine screw will probably work as well, but will strip the
plastic easier and not hold as well. I have only one screw holding
mine together and it works fine.
You will probably need to re-shape your tin overlay, as it probably
took a beating during removal. I removed the sticky tape from mine,
but it's probably better not to (unless it really wont stick anymore).
Put wax paper over the tape and put the overlay face down on a hard
cover book. Grab a hammer with a smooth and somewhat flat head, and
pound away. DONT pound away on the part that surrounds the screen
(beveled part). You can probably use your fingers and a little
massaging to fix that area. With a little care you can end up with an
overlay that looks like new. Press the overlay in place and hope it
sticks. If not, a little rubber cement wouldn't hurt.
Have fun!
Paul Smith
v055qmd6@ubvms.cc.buffalo.edu
++++++++++++++++ end forwarded text ++++++++++++++++++
--
David Fenyes dave@msrad74.med.uth.tmc.edu
University of Texas Medical School Houston, Texas