cac@iear.arts.rpi.edu (Christopher A. Cox) (04/13/91)
I have recently gotten my hands on an IBM Professional Graphics Display. This is a somewhat older beast, though mine is brand new (purchased at an auction). I have heard that there was someone out there who managed to get it to work with a standard VGA card. This is what I'm trying to do. So far it looks possible. I think that the monitor must be analog (though possibly not). I have pinouts, and they indicate that the color pins are in the right place, but the sync and mode select ones aren't. It may be that I can just solder something together, but since I am told that someone else has done so it would be nice to get the info that way (and save me screwing up the monitor). Thanks... Chris -- ---------- If you cut here you'd probably ruin your monitor ------------- Christopher A. Cox I think, therefore cac@iear.arts.rpi.edu I am confused. cac@orac.stu.rpi.edu
berger@iboga (Mike Berger) (04/18/91)
cac@iear.arts.rpi.edu (Christopher A. Cox) writes: > So far it looks possible. I think that the monitor must be >analog (though possibly not). I have pinouts, and they indicate that >the color pins are in the right place, but the sync and mode select ones >aren't. It may be that I can just solder something together, but since >I am told that someone else has done so it would be nice to get the info >that way (and save me screwing up the monitor). Thanks... *---- Mendelson Electronics in Ohio sells modified PGA monitors for VGA use. I looked at the PGA schematics. Although the interface is analog, it's a current rather than a voltage interface. I don't think it would take more than a few op amps to make a proper interface. -- Mike Berger Department of Statistics, University of Illinois AT&TNET 217-244-6067 Internet berger@atropa.stat.uiuc.edu
gp310ad@prism.gatech.EDU (ROBERT DUCKWORTH) (04/18/91)
Hi-
The IBM PG monitor is an analog RGB monitor requireing a composite
sync signal (horizontal and vertical mixed)..
The monitor supports two modes. 640x480 and 640x400. The mode is
changed by pulling the mode line low.
The VGA monitor is an analog RGB monitor. It requires a split sync
signal (horizontal and vertical on separate wires).
The monitor supports 3 modes. 640x480, 640x400, and 640x350. The
mode information is in the polarity of the sync signal.
Inside the PG monitor the composite sync is split into vertical
and horizontal components (pretty easy with an RC filter as one is
10's of kilohertz and the other is 10's of hertz). This is a good place
to put the new sync signals in. The problem is that the polarity has to
be right.
So, how do we change the varying polarity of the VGA to the constant
polarity required by the PG? I used a quad exclusive or and some R and some
C. This circuit goes on a small board inside the monitor. It is held in
place with hot melt glue or double sided foam tape. Barge cement should
do a good job too.
What about the mode? Well, the caps hold the average value of the sync
signal and can spare enough juice to turn on a 2n3904. this signal goes to
the old mode input (gives you two modes). Pick the two that fit the SW you
use or..........
The mode is changed by switching in some trimmers on the vertical 'chip'
They are switched by one section of a quad 2 to 1 mux (or a 4pdt analog
switch if you prefer). here is enough room on the board to replace this
with a dual 4 to 1 mux (2p4t switch). Add an extra trimmer and you are 100%
VGA compatible.
I made boards and bought parts for 1000 kits. We converted 800 monitors
and sold all the other kits. So, I'm out of kits.
If there is sufficient interest here, I will gather parts for some more kits.
Kits include everything needed for a complete (to 100% VGA compatibility)
conversion.
Manual, 15pin connector, syncfix (copyright) board, trimmer, wire, and all
components. Complete kits are $39.95 and also work with many other surplus
monitors requiring a 'fixed' sync.
I highly recommend NOT generating a composite sync signal. The additional
delay caused by the sync fixing circuitry and then by mixing the sync
signals puts the sync behind the dots enough to make it difficult to adjust
many monitors.
As for the kits, I will need a minimum of 10 orders to cover the cost of
a minimum board run. It will take about 3 weeks from the time I know there
is enough interest til the time all the parts are here and ready to ship.
Feel free to roll your own. There's enough info here to do it. :-)
Have fun and watch out for sharp edges and HIGH VOLTAGE inside the PG.
Also, be careful of the tube neck.
Try out your monitor before converting. There is generally enough brightness
to see if you get a raster. If you do, It's probably good. If you have
problems with 'pincusion' it's most likely from component aging in the E-W
amp. Another common problem area with this monitor is the connection
between the video board and the main board. Clean the contacts if the colors
are off a little or if one is completely missing and you know it is getting
to the input side of the video board.
Bob
--
Bob Duckworth -everything you know is wrong-
Earth & Atmospheric Sciences, Georgia Tech, Atlanta, 30332
uucp: ...!{allegra,amdmhplabs,ut-ngp}!gatech!prism!gp310ad
Internet: gp310ad@prism.gatech.edu 404-894-3890(o) 874-5051(h) 313-0095(m)