Parallel Port LPT2 / LPT3 Modification

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chuckphd53
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Parallel Port LPT2 / LPT3 Modification

Post by chuckphd53 »

Want to have TWO parallel ports on your JR ? OR THREE ?

I did these mods along while back....
So this is the original write up as it appeared back then...
I found some original pictures I did, so excuse the quality ! :roll:

MODIFICATION TO CHANGE THE STANDARD

IBM PCJR LPT1 SIDE CAR TO PORT LPT2

Charles L. Terra PhD PE
chuck1953@bellsouth.net


You can use any program that checks the ports to test your modification.
I did this mod because I wanted to add a ZIP drive to my Jr and wanted
to have a free (non-ZIP port) LPT for other uses....

I used a program from Klaus Peichl, name: LPT_TEST.com this is available on the internet.
This program tests for Bi-Directionality of a LPT port.

Caution:
When using this program, if you only have one Printer sidecar installed, the
the program will report this port as ( LPT1 H278 ), this is confusing because it is really
( LPT2 ). But if you install two LPT sidecars, one standard and one with
this mod it will give the right reports back.....

1: REMOVE PCB FROM PLASTICS

2: ORIENT BOARD SO IT IS THE SAME IN THE PICTURE LABELED (SIDE 1)

3: LOCATE THE TRACE BETWEEN CHIPS 74LS04 AND 74LS30 (SEE PICTURE)

4: USING A SHARP EXACTO KNIFE MAKE A SMALL CUT TO ENSURE THE COPPER TRACE IS
REMOVED....BE CAREFUL NOT TO DAMAGE ANY OTHER TRACES.
IT SHOULD LOOK LIKE THE PICTURE (SIDE 1)

5: USING A SMALL 30AWG WIRE, CUT AND STRIP THE WIRE ENDS, SOLDER ONE SIDE
TO PIN 2 (74LS04), THEN SOLDER THE OTHER SIDE TO PIN 4 (74LS30).
MAKING SURE NOT SO 'SOLDER BRIDGE' BETWEEN ANY OF THE ADJACENT PINS.

MODS FOR SIDE 1 ARE DONE ....CONGRATULATIONS.....

1: TURN BOARD OVER AND POSITION IT AS SHOWN IN PICTIRE (SIDE 2)

2: LOCATE THE TRACE SHOWN ON THE PICTURE.. (BE SURE YOU HAVE THE RIGHT ONE)
IT'S BEST TO DOUBLE CHECK AND MARK IT WITH A RED PEN IF NEEDED SO YOU
DON'T LOOSE SITE OF IT...

3: USING A SHARP EXACTO KNIFE MAKE A SMALL CUT TO ENSURE THE COPPER TRACE IS
REMOVED....BE CAREFUL NOT TO DAMAGE ANY OTHER TRACES.
IT SHOULD LOOK LIKE THE PICTURE (SIDE 2)

4: USING A SMALL 30AWG WIRE, CUT AND STRIP THE WIRE ENDS, SOLDER ONE SIDE
TO POINT SHOWN IN THE PICTURE, THEN LOCATE THE OTHER POINT AND DO THE SAME.
(AGAIN IT'S BEST TO MARK THIS WITH A RED MARKER TO HELP KEEP TRACK OF IT.)

MODS FOR SIDE 2 ARE DONE ....CONGRATULATIONS.....

YOU ARE NOW DONE AND THE SIDECAR IS SET UP FOR PORT LPT2 PORT ADDRESS H278

Feel free to pass this along but keep all the files in tack....

Chuck....
Image

Image

MODIFICATION TO CHANGE THE STANDARD

IBM PCJR LPT1 SIDE CAR TO PORT LPT3

Charles L. Terra PhD PE
chuck1953@bellsouth.net

This is a preliminary document:

Step 1:
Preparing the pins on chips that need modification.
Using LPT3_1 as a reference...

You will be clipping the pins, removing half of the pin that goes thru the pc board
being careful not to cut off the entire pin,you will need to solder jumper wires
to the remaining portion connected to the chip....

Definition: VIA : this is the hole that the chip pin goes in, it make electrical
contact from the top of the board to the bottom of the board. I'll reference the
VIA in this document.

First using solder wick, remove as much solder as you can, be sure not to heat the
pins up too much...(A solder sucker is prefered, does a much better job)

After cutting the pin, clean the via removing any excess solder from the via. You can do
this from the bottom of the board best.
Now gently bend the remaining portion of the chip pin up away from the board. You will
need to solder a jumper wire in the newly cleaned Via and to the remaining chip pin.

Using the numbers on the chips...prepare all the chip pins and via's as described above:

(CHIP 1) cut and prep pins 5 and 11

(CHIP 2) cut and prep pins 4,5 and 6

(CHIP 3) You will need to ADD a chip 74LS08 as seen in the picture.
You will only use pins 1,2,3,7 and 14.
Cut all but pins 7 and 14 leads back, typically in half will be fine.

Bend pins 7 and 14 down and solder them to the chip located in the picture
directly below the added chip. This will supply power (pin14) and ground (pin7)
to the new chip. Make sure you BEND out the remaining pins so they do not
touch any pin on the chip below....

Step 2:
Adding Jumper wires to the board:
(note: ignore the jumper wire labeled Bi-Dir, this is the Bi-Directional mod, not part
of this documentation.)

Note: Defintion Pin - part of the chip
Via - hole below the chip pin designated

Jumper 1:
Connect a wire from :

CHIP 1-pin 5 to CHIP 2- pin 4

CHIP 1-pin 11 to CHIP 3- pin 3

CHIP 3-pin 2 to CHIP 1- via 11

CHIP 2-pin 5 & 6 to CHIP 1- via 5

Important steps to pay attention to here:

CHIP 3-pin 1 to Connector B7 (See LPT3_2 picture)
Notes:
Look at the picture and locate the VIA that the wire goes through.
This is just to get the wire from one side of the board to the other,
It DOES NOT get soldered to this via. Think of it as a doorway....

(be careful not to place too much solder on the connector pin, it is best to prep the
pin by placing a small abount of solder on it first, then with a hot iron
just tack solder the wire on)

JUMPER:
Again using LPT3_2 picture, locate the small jumper just above the connector
to the left.
This is the bottom side of CHIP 2 and will jumper pin 4 to pin 6.

DONE.
Check your work before powering up the unit.
Image

Image


Down Load the instructions
https://www.pcjribm.com/pcjrfiles/ibmlpt2mod.txt
https://www.pcjribm.com/pcjrfiles/ibmlpt3mod.txt
“I never commit to memory anything that can easily be looked up in a book.” (AE)

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