IBM 8503 Monochrome VGA Monitor - Cut cable!

User avatar
DeChief

31 Jan 2019, 06:14

Hey all. I was recently given an IBM model 8503-004 monochrome monitor but the VGA cable has been cut. Would anyone happen to have this same monitor and be able to open theirs up? It would be very simple to figure out the pinout - the cable connects inside to the neck board and mainboard using 2 sockets, you would just have to use a multimeter in continuity mode to figure out which wire goes to which pin on the VGA connector.

If not, does anybody have a service manual or schematic for the monitor?

Here are some photos so you have a better idea of what I'm talking about:
https://imgur.com/a/Q8Vt7uJ

Hoping somebody can help me out on this. I'd love to be able to use the monitor with my IBM PS/55! :blush: (cross-posted from vogons.org btw, just for reference)

Polecat

31 Jan 2019, 07:04

I have a couple IBM mono VGA monitors here, but they're the smaller POS ones,. 4689 and 4707 (same except the cable length), and I'm pretty sure the cables aren't the same as the 8503.

edit: should say 4683 and 4707

But most of what you need is labelled on the PC board, thanks to IBM! There will be several signal grounds, plus horizontal and vertical sync (HS & VS), and a single ("green") video line (the center on the 3 pin plug). Also pin 12 will need to be grounded so the video card can ID the monitor as a mono VGA. Here's my old notes on the computer end (not specifically for the 8503):

VGA Monitor Connections

Mini 15
Pin # Signal

1 Red Video (mono-not used)
2 Green Video (mono video)
3 Blue Video (mono-not used)
4 Monitor ID Bit 2 (not always used)
5 Ground
6 Red Return (Ground)
7 Green Return (Ground)
8 Blue Return (Ground)
9 Key (no pin)
10 Sync Return (Ground)
11 Monitor ID Bit 0 (color) (not always used)
12 Monitor ID Bit 1 (mono) (not always used)
13 Horizontal Sync
14 Vertical Sync
15 Not Used

Note that on monochrome VGA monitors pin 11 is grounded, on color
VGA pin 12 is grounded. This allows the VGA card to poll the
monitor port to determine whether a monochrome or color monitor is
present. If color software will not work on a monochrome monitor,
the card can be "fooled" by installing a switch that alternately
grounds pin 11 or 12. The machine must be rebooted after flipping
the switch for it to recognize the setting. Source - PC Magazine,
August 1989. 11.8.91
Last edited by Polecat on 01 Feb 2019, 06:27, edited 1 time in total.

User avatar
DeChief

31 Jan 2019, 08:57

Wow, that was fast, thank you so much for the help! I also got a reply on VOGONS (https://www.vogons.org/viewtopic.php?f=46&t=65050) so I should be able to wire this up now, but I bet I'll be back to ask a stupid question at some point :lol:

Polecat

01 Feb 2019, 06:22

DeChief wrote:
31 Jan 2019, 08:57
Wow, that was fast, thank you so much for the help! I also got a reply on VOGONS (https://www.vogons.org/viewtopic.php?f=46&t=65050) so I should be able to wire this up now, but I bet I'll be back to ask a stupid question at some point :lol:
No such thing as stupid questions, only stupid answers, but I've got plenty of those. I'm pretty much incidental to this site, just happened onto your question. But I repaired thousands of CRT monitors back in the day, and I've done a lot of adapting and converting also. Nobody wanted mono VGA monitors back in the '90s, they were literally free for the taking. My favorite thing to do was to use the electronics from a 12 or 14 inch mono VGA monitor on a 9 inch CRT and install it in a portable case like a Kaypro along with a mini AT 386 or 486 motherboard. Unlike a color CRT a mono one has no shadow mask, and therefore no dot pitch, so the resolution is only limited by how tightly you can focus the electron beam. That's why the display on the early Macs looked so nice, and a 640 by 480 or 800 by 600 mono VGA display is really sharp and easy on the eyes.

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