Easy instructions for making an HP48 to PC link cable
By Vimal Bhalodia


Hi, for all you cheap folks out there who want to know how to make a 
serial port connector type thing (aren't I so technical) here is a 
quick way using things around the house, or available very cheaply.

BTW:	I am extremely overprotective of my calculator, and will not 
do anything to harm it. I do NOT make any guarantees, but there 
doesn't seem to be any possible way to damage your calculator's serial 
port. Now, damage to the fingers may be another matter...


Things needed:

1.	Precision Screw Driver Set
2.	9 pin female serial port (the ones with holes, as opposed to 
	pins)
3.	Rubber Erases (I personally prefer the pink ones)
4.	Razor Blade

Step 1

Take the eraser and place it flat on a table. If it has tapered edges, 
chop off, with razor blade,  ends, so that it is perfectly, or as 
close as possible, rectangular.

It should now look like a long box.

Step 2

Stand the eraser up on end, and look down from the top. Looking down 
from the top, turn the eraser until the longer edge is horizontal, and 
the shorter edge is vertical. Make sure that the shorter edge of the 
eraser is about 7/16" long. If not, shave the top of the eraser until 
it is close to that long. (A knife blade is quickest, but for the 
safety conscious, get a piece of sandpaper, and rub the face you want 
to shave until you get the desired measurements.)

It should now still look like a long box.

Step 3

Still looking at the eraser from the top while it is standing on one 
end, measure in from one vertical edge about 3/16" Make a vertical 
slice into the eraser going straight down, or as close as possible. 
Once your slice, still looking from the top, is about 3/4" deep, pull 
the little part away from the eraser, ripping the eraser at the back. 
Take that little part and lay it flat on a table. The front is the 
flat, smooth edge. The back is the stringy, slanted tapered edge. Chop 
off the back until it is also flat and smooth, perpendicular to the 
table. This should now make a complete rectangle. Make sure that when 
you chop off the end, you are still at least 1/2" from the front.

You should now have a little tiny rectangular box, 7/16" wide, 3/16" 
high, and 1/2" long. Close enough in this part is good enough.

Step 4

The 3/16" by 7/16" face is the front face. Take it, and push it into 
the calculator's wire port. Make sure that when you push, you push far 
enough for there to be some resistance, but not so far that you can't 
easily remove the eraser.

Take out the eraser, and look at the ends. You should see little marks 
corresponding to where the pins in the wire port are.

Step 5

Probably the most difficult to do correctly. Looking down on the face 
of the block, where the mark is, take the smallest precision 
screwdriver you have, usually 0.9 mm, and push it down through the 
eraser, starting at each of the four marks, and going all the way 
through the back.  Make sure the individual holes do not connect with 
each other. This may take a couple of tries on several little blocks, 
(15 for my first try, went through 5 whole erasers) but a tip to make 
it easier is look at the screwdriver and block from different angles 
while pushing. Also the furthest left hole can be angled a little to 
the left, the middle left hole a little up, the middle right hole a 
little down, and the furthest right hole a little to the right. It 
does not matter exactly where the holes end up on the other side, as 
long as they are isolated and intact.

Step 6

Now, to make the holes bigger, starting from the front end, where you 
first pushed the screwdriver, push it again through the same path, 
except for this time, keep it constantly twisting and turning. Do 
this from the other side as well. Repeat these steps for the other 
three holes

Step 7

Now, for the actual serial part: get a 9 pin female serial connector. 
You may chop one off from an actual cable, or just buy the terminal 
from Radio Shack for $1.49 or something like that. Look at the front 
of the connector, where all the holes are. The HP uses only the top 
row. Separate the wire that goes into, or corresponds to the hole 
furthest to the left in the top row. Label that wire #5. Separate the 
wire 2 places to the right, in the middle of the top row. Label that 
wire #3. Separate the wire next to the previous wire, second from the 
right. Label that wire #2. Separate the wire all the way to the right. 
Label that wire #1.

Step 8

Inserting the wires into the eraser block. Orient the eraser so that 
the end that was pushed into the calculator is facing away from you 
and the eraser is in the same position as it would be if it were going 
to be plugged into a calculator. The front of the calculator is facing 
you, with the LCD facing up and the keys upside down. Take wire #5, 
and strip about 1/2" from the free end. Twist the little strands in 
the wire together. Bend the stripped part of the wire roughly in half, 
to make a hook. Hook that wire onto the end of the smallest 
screwdriver. Push the screwdriver and the wire into the hole furthest 
to the right on the back of the eraser block. That hole should 
correspond to the pin furthest to the right when looking at the HP48 
wire port. Keep pushing the screwdriver and wire into the hole just 
until you see the wire coming out the other end. Then, carefully 
remove the screwdriver, leaving the wire inside the hole. Repeat this 
for the other wires. Wire #3 should go into the hole second to the 
right. Wire #2 should go into the hole second to the left, and wire 
#1 should go into the hole all the way to the left.

Step 9

Optional: You may want to put a little hot glue around the back of the 
wires to keep them firmly in place, and prevent them from getting 
pushed out.

Step 10

Congratulations, you made the serial link. Go out, get drunk, pass 
out, and wake up the next morning.

Step 11

Now that you made the cable, try it out. Push it into the wire port 
and make sure it goes in snugly. If you push too hard, you may be 
pushing a wire out, so be careful. This design worked for me, and I 
made three link cables. (Two of them, unfortunately, used male serial 
connectors, instead of female) 



The most damage you can possibly do to your HP48 is to have some 
little eraser crumbs rattling around inside. This is a pretty safe bet 
for a cable, and involves no soldering, measuring, etc. okay, well, 
maybe a little, but it can all be done by an amateur. I've only had my 
HP48G for 2 months.


Written By:	Vimal Bhalodia 5/4/98

Since I've already made a more or less successful cable, I could care 
less about your comments (just kidding), but I'm sure other people 
would. Please feel free to take this text, revise, modify, clarify, or 
expand on any parts you wish to and resubmit it. Please mention your 
name and the date.

Note:	Pictures of the process would be much appreciated, even if 
only in ASCII.

Revised By:	Eric Rechlin 5/4/98