7 Jun
2023
7 Jun
'23
11:26 a.m.
Hello!
I have an IBM 6152 aka IBM RT system I rescued. (It may be a 6151?)
I'm 90% sure it has colour graphics. The system does seem to POST
correctly (according to the LED on the front) but the CRT is dead. I'm
wondering if anyone has built an adapter to hook this to a VGA
monitor.
I'm a bit confused by the pinout. It has high and low bits for the RGB
(and associated grounds for each colour.) So I'm not sure how that
would work hooking to a more modern monitor.
http://bio.gsi.de/DOCS/IBM/615x/faqshard.html
Otherwise I need a crash course in fixing CRTs.
--
-Jon
+44 7792 149029
7 Jun
7 Jun
11:44 a.m.
On 06/07/2023 1:26 PM CDT Jonathan Katz via cctalk
<cctalk(a)classiccmp.org> wrote:
Hello!
I have an IBM 6152 aka IBM RT system I rescued. (It may be a 6151?)
I'm 90% sure it has colour graphics. The system does seem to POST
correctly (according to the LED on the front) but the CRT is dead. I'm
wondering if anyone has built an adapter to hook this to a VGA
monitor.
I'm a bit confused by the pinout. It has high and low bits for the RGB
(and associated grounds for each colour.) So I'm not sure how that
would work hooking to a more modern monitor.
http://bio.gsi.de/DOCS/IBM/615x/faqshard.html
Otherwise I need a crash course in fixing CRTs.
--
-Jon
+44 7792 149029
I am not familiar with any of that equipment, but from the description here
http://bio.gsi.de/DOCS/IBM/615x/faqshard.html#h33. it appears the video is two bits of ttl
level data for each color. That is how EGA did it, which I think was about the same time
frame (1985 ish.). The scan rates seem rather close to EGA as well. It might be
worthwhile to look into EGA interfacing.
Will
11:52 a.m.
I know that VGA used analog signals and sync rather than digital signals.
On 6/7/2023 1:44 PM, Will Cooke via cctalk wrote:
On 06/07/2023 1:26 PM CDT Jonathan Katz via
cctalk <cctalk(a)classiccmp.org> wrote:
Hello!
I have an IBM 6152 aka IBM RT system I rescued. (It may be a 6151?)
I'm 90% sure it has colour graphics. The system does seem to POST
correctly (according to the LED on the front) but the CRT is dead. I'm
wondering if anyone has built an adapter to hook this to a VGA
monitor.
I'm a bit confused by the pinout. It has high and low bits for the RGB
(and associated grounds for each colour.) So I'm not sure how that
would work hooking to a more modern monitor.
http://bio.gsi.de/DOCS/IBM/615x/faqshard.html
Otherwise I need a crash course in fixing CRTs.
--
-Jon
+44 7792 149029
I am not familiar with any of that equipment, but from the
description here http://bio.gsi.de/DOCS/IBM/615x/faqshard.html#h33. it appears the video
is two bits of ttl level data for each color. That is how EGA did it, which I think was
about the same time frame (1985 ish.). The scan rates seem rather close to EGA as well.
It might be worthwhile to look into EGA interfacing.
Will 
11:52 a.m.
On Jun 7, 2023, at 11:26 AM, Jonathan Katz via cctalk
<cctalk(a)classiccmp.org> wrote:
Hello!
I have an IBM 6152 aka IBM RT system I rescued. (It may be a 6151?)
You have a 6151, the 6152 has VGA graphics (is built inside a PS/2 Model 60)
I'm 90% sure it has colour graphics. The system
does seem to POST
correctly (according to the LED on the front) but the CRT is dead. I'm
wondering if anyone has built an adapter to hook this to a VGA
monitor.
You’re going to run into trouble, then, as the video signal is completely incompatible
with a normal VGA multisync monitor. It’s TTL color, interlaced, with a horizontal scan
frequency less than 31kHz. 720x512 interlaced.
The RT knows how to use a “standard” IBM PC MDA or EGA adapter. Might be better off using
one of those instead, at least for now.
ok
bear.
8:06 p.m.
On Wed, Jun 7, 2023 at 11:54 AM r.stricklin via cctalk
<cctalk(a)classiccmp.org> wrote:
All of the IBM RT 6151 systems I saw years ago (ugh, 36 years ago
now...) must have all had Megapel display adapters attached to
monochrome or grayscale monitors. That was the early days of Project
Athena and X11. At the time they seemed like reasonably nice systems,
comparable to the more common VAXstation 2000 systems. I imagine if
you have an IBM RT 6151 system now without a Megapel display adapter,
it would probably be difficult to find one.
On Jun 7, 2023, at 11:26 AM, Jonathan Katz via
cctalk <cctalk(a)classiccmp.org> wrote:
Hello!
I have an IBM 6152 aka IBM RT system I rescued. (It may be a 6151?)
You have a 6151, the 6152 has VGA graphics (is built inside a PS/2 Model 60)
I'm 90% sure it has colour graphics. The
system does seem to POST
correctly (according to the LED on the front) but the CRT is dead. I'm
wondering if anyone has built an adapter to hook this to a VGA
monitor.
You’re going to run into trouble, then, as the video signal is completely incompatible
with a normal VGA multisync monitor. It’s TTL color, interlaced, with a horizontal scan
frequency less than 31kHz. 720x512 interlaced.
The RT knows how to use a “standard” IBM PC MDA or EGA adapter. Might be better off using
one of those instead, at least for now.
ok
bear. 
8 Jun
8 Jun
3:12 a.m.
On Wed, Jun 7, 2023 at 2:26 PM Jonathan Katz via cctalk <
cctalk(a)classiccmp.org> wrote:
I have an IBM 6152 aka IBM RT system I rescued. (It
may be a 6151?)
I'm 90% sure it has colour graphics. The system does seem to POST
correctly (according to the LED on the front) but the CRT is dead. I'm
wondering if anyone has built an adapter to hook this to a VGA
monitor.
Do you have the Megapel adapter in your 6151 with the 3W3 connector? I
have one in my 6150 and I was able to connect it to a VGA monitor (NEC
Multisync) and I think I only created an adapter to go from 3W3 to Red,
Green and Blue RCA plugs (component) that then went into a simple RGB
component to VGA wired adapter (about 6 inches long) I already had. Part
of the magic might be in that multisync monitor though.
Here it is running AIX:
https://vintagecomputer.ca/wp-content/uploads/2023/06/IBM_PC_RT_running_AIX…
I got the 3W3 connector and parts from Digikey. Here's what that looks
like:
https://vintagecomputer.ca/wp-content/uploads/2023/06/IBM_RT_3W3_RGB-rotate…
Please forgive the crude construction. I didn't think it would work but it
did.
Here is the RGB component to VGA adapter I also used:
https://vintagecomputer.ca/wp-content/uploads/2023/06/RGB2VGAadapter.jpg
Hope this helps.
Santo
4:34 a.m.
On 2023-06-08 06:12, Santo Nucifora via cctalk wrote:
I got the 3W3 connector and parts from Digikey.
Here's what that looks
like:
https://vintagecomputer.ca/wp-content/uploads/2023/06/IBM_RT_3W3_RGB-rotate…
Please forgive the crude construction. I didn't think it would work but it
did.
You still have the part numbers?
5:20 a.m.
Looking back, I did buy one from Digikey but it was not the right one.
I bought mine from this ebay auction: https://www.ebay.com/itm/171649843131
Specifically, the "D-SUB 3W3 Male" item. I did not install the three metal
coax covers that come with it. The end looks like this:
https://vintagecomputer.ca/wp-content/uploads/2023/06/IBM_RT_3W3_end.jpg
Hope this helps.
Santo
On Thu, Jun 8, 2023 at 7:34 AM emanuel stiebler <emu(a)e-bbes.com> wrote:
On 2023-06-08 06:12, Santo Nucifora via cctalk
wrote:
I got the 3W3 connector and parts from Digikey.
Here's what that looks
like:
https://vintagecomputer.ca/wp-content/uploads/2023/06/IBM_RT_3W3_RGB-rotate…
Please forgive the crude construction. I
didn't think it would work but
it
did.
You still have the part numbers?
9:06 a.m.
On Thursday, June 8, 2023 at 05:20:28 AM PDT, Santo Nucifora via cctalk
<cctalk(a)classiccmp.org> wrote:
I bought mine from this ebay auction:
https://www.ebay.com/itm/171649843131
Specifically, the "D-SUB 3W3 Male" item.
[...]
Note these are 50 Ohm impedance. I always assumed the OEM originals were 75 Ohm.
I've not been able to find 75 Ohm equivalents in the past 3 years I've been
looking.
OTOH I'm not a hardware person, I have no idea if a ~1.5cm-long connector matters,
especially if it's connected to a non-coaxial VGA cable, then to the VGA input of a
multi-sync flat panel display. (I'm not sufficiently retro to want to go back to
carrying 19in sync-on-green CRTs)
9:32 a.m.
On 6/8/23 11:06, Jonathan Stone via cctalk wrote:
On Thursday, June 8, 2023 at 05:20:28 AM PDT, Santo
Nucifora via cctalk<cctalk(a)classiccmp.org> wrote:
A 1.5" long pigtail of the wrong impedance would have very
little effect if the pixel clock is under 100 MHz. A 2 M
long VGA cable with a bunch of wires in a shield DEFINITELY
causes visible artifacts on a mid-frequency VGA. A long
time ago I actually had to make my own VGA cables with HD15
connectors and RG-178 cable, because stock cables were total
crap!
Jon
I bought mine from this ebay
auction:https://www.ebay.com/itm/171649843131
Specifically, the "D-SUB 3W3 Male" item.
[...]
Note these are 50 Ohm impedance. I always assumed the OEM originals were 75 Ohm.
I've not been able to find 75 Ohm equivalents in the past 3 years I've been
looking.
OTOH I'm not a hardware person, I have no idea if a ~1.5cm-long connector matters,
especially if it's connected to a non-coaxial VGA cable, then to the VGA input of a
multi-sync flat panel display. (I'm not sufficiently retro to want to go back to
carrying 19in sync-on-green CRTs)
9:49 a.m.
On Jun 8, 2023, at 12:06 PM, Jonathan Stone via cctalk
<cctalk(a)classiccmp.org> wrote:
On Thursday, June 8, 2023 at 05:20:28 AM PDT, Santo Nucifora via cctalk
<cctalk(a)classiccmp.org> wrote:
Normal VGA connectors are DE-15, which have no defined impedance in the first place. No,
short unmatched segments like that don't matter at all, not at VGA frequencies.
If a cable claims to be VGA but isn't coax I would call it fake. An actual cable
carrying video signals does need to be coax, and does need to be the correct impedance
(i.e., 75 ohms).
paul
I bought mine from this ebay auction:
https://www.ebay.com/itm/171649843131
Specifically, the "D-SUB 3W3 Male" item.
[...]
Note these are 50 Ohm impedance. I always assumed the OEM originals were 75 Ohm.
I've not been able to find 75 Ohm equivalents in the past 3 years I've been
looking.
OTOH I'm not a hardware person, I have no idea if a ~1.5cm-long connector matters,
especially if it's connected to a non-coaxial VGA cable, then to the VGA input of a
multi-sync flat panel display. (I'm not sufficiently retro to want to go back to
carrying 19in sync-on-green CRTs)
5:08 p.m.
On 2023-06-08 08:20, Santo Nucifora wrote:
Looking back, I did buy one from Digikey but it was
not the right one.
I bought mine from this ebay auction:
https://www.ebay.com/itm/171649843131
<https://www.ebay.com/itm/171649843131> Specifically, the "D-SUB 3W3
Male" item. I did not install the three metal coax covers that come
with it. The end looks like this:
https://vintagecomputer.ca/wp-content/uploads/2023/06/IBM_RT_3W3_end.jpg
<https://vintagecomputer.ca/wp-content/uploads/2023/06/IBM_RT_3W3_end.jpg>
Hope this helps.
Santo
Hello Santo, looks good, just ordered some.
THANKS!
344
days inactive
346
days old
11 comments
10 participants
participants (10)
-
emanuel stiebler -
Glen Slick -
Jon Elson -
Jonathan Katz -
Jonathan Stone -
Mike Katz -
Paul Koning -
r.stricklin -
Santo Nucifora -
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