IBM PC-jr color monitor conversion to EGA
Todd Barth
-
Does anyone know if the 80 column color monitor which was shipped with an
IBM PC-jr computer (remember this one?) can be adapted for use on a standard
CGA or preferably an EGA card in an ordinary PC (or clone)? The connector
certainly needs to be changed, but I don't know what the pinout is or if
the monitor is composite or RGB or ??
The PC-jr it came with has bit the dust, and I don't wish to fix it, however
the display quality of the monitor is good enough that I would like to save
it for use on a standard PC with EGA (or CGA if that is all that will work).
Thank you in advance.
Todd Barth N6NFG 224.720 -
Tolerant Systems 81 E Daggett Drive, San Jose CA 95134
(408) 433-5588
Kurt Grutzmacher
These are the pin assignments for the signals on the PCjr Color
Display, and the corresponding pins on a PC Color/Graphics Adapter
output connector.
The PCjr Color Display uses a 18 pin 2 row "Berg" connector, with
pins on 0.1 inch centers. The color/graphics adapter uses a 9 pin
"D" connector.
In order to be able to use the PCjr display with a regular PC, it is
necessary to provide an adapter cable, having a male 18 pin Berg
connector at one end, and a male 9 pin D connector at the other.
I made such a cable, and have successfully used my PCjr display with
an IBM Portable personal computer. Sure eliminates eyestrain!
PCjr RGB output is: PC C/G Adpt output pin is:
A01 - TV vert drive .................... n/a
A02 gnd .............................. 1
A03 - TV horz drive .................... n/a
A04 blue ............................. 5
A05 red ............................... 3
A06 inten ............................. 6
A07 green ............................. 4
A08 - comp sync drive .................. n/a
A09 audio out ........................ n/a
B01 + vert drive out ................... 9
B02
B03 + horz drive out ................... 8
B04 gnd
B05 gnd..............................2
B06 gnd
B07 gnd
B08 gnd
B09 gnd - frame
It is not too obvious just which pin is which, especially on
the PCjr's connector. So...here is the pin layout as you look into the
holes on the CGA and the Display's connector:
1 o 1-A2 letter "D" stamped on top
o 6 2-B5
2 o 3-A5 9 8 7 6 5 4 3 2 1
o 7 4-A7
3 o 5-A4 A o o o o o o o o o
o 8 6-A6 B o o o o o o o o o
4 o 7-unused
o 9 8-B3
5 o 9-B1
To make the cable, you will need an 18 (or 16) pin "header". The
easiest place to obtain one of these is your neighborhood Radio
Shack. They have a "Header Assortment", Part #276-1658, for $1.98.
Select an assortment that has at least one connector that has two
rows of either 8 or 9 pins. I have not been able to find any that
have 9 pins, but one that has two rows of 8 is acceptable, because
pins A9 and B9 will not be used in making the cable. The header
connectors are really intended for use with printed circuit boards,
and the 'wiring' side of the connector has pins which have a right-
angle bend to facilitate soldering them to the circuit board.
Cut the free end of the bent pins just above the bend. You will
be soldering to these pins.
The other connector you will need is a 9 pin male "D" connector,
Radio Shack Part # 276-1537 ($1.99). You will also want a hood for
this connector....Part #276-1539 ($1.99) Also needed: about 30
inches of #22 or smaller thermoplastic insulated hookup wire,
some plastic electrical tape, and a tube of either Dow-Corning
(RTV) or G.E. silicone rubber adhesive.
Tools needed: a small (30 watt maximum) soldering iron, fine
(.0625" diameter) rosin core solder, small long nose pliers, wire
cutter & stripper, and a small (1/8" blade) screwdriver.
Cut eight 3-inch pieces of hookup wire, and strip 1/4 inch of insulation
off each end. Solder these wires as follows:
D connector pin 1 to header pin A1
D connector pin 2 to header pin B5
D connector pin 3 to header pin A5
D connector pin 4 to header pin A7
D connector pin 5 to header pin A4
D connector pin 6 to header pin A6
D connector pin 8 to header pin B3
D connector pin 9 to header pin B1
Check all connections carefully. You can bunch the wires together and
wrap them with electrical tape after checking the finished cable.
Now for the test.....since you are probably using an 8 pin header, remember
which end is pins 1, (easy, because both #1 pins have wires on them) and
which is the A side of the connector (the one with the most wires).
With the A side up, and the pins facing you, pin 1 is to the left.
Plug the header into the PCjr display cable....the A side of the
cable connector is the one having the "D" on the metal shell. Make
sure that pin 1 of the header mates with pin 1 of the display cable
connector. Plug the D connector into the mating connector on the
C/G adapter card on your PC. Turn on the power....if you did
everything right, your jr display should work like a champ!
If all is ok, remove the adapter cable, and complete the job:
You can now make a compact bundle of the wires between the two
connectors. Wrap carefully with plastic tape. Using a popsicle
stick or something similar as a modeling tool, fill the space around
the pins on the wire side of the header with silicone adhesive, leaving
no exposed metal. The silicone rubber is an excellent insulator, and
will substitute for a hood over the exposed pins. Install the hood
on the "D" connector, and the job is done! Total cost, less than $7.00
Good luck!
Charlie Dose' 75116,1164
it was long, but this is it! gotta be sure that you get everything hooked
up together TIGHT! I made the mistake of wanting to also still use my
monitor on the JR, and I didn't want to buy an adapter... so I split the
monitor cable, and now I have lose wires... sometimes get really fuzzy
characters... especially in HIGH INTENSITY ones. but it works on my XT!