Hi
Thanks for the detailed information. Having found the full set of
docs in the box plus my what I remember from DEC, as I was there when
this kit was current. I had a general idea as to how it worked. As my
other hobby is amateur television (I build ATV repeaters) at least I was
able to understand what you said.
As to the VR241 I agree. A non working one would be a bit of a
challenge. I'm trying to think of another DEC RGB monitor from around
that time that might have been used. Do you know I can't actually
remember if the one I had at DEC had one monitor or two. My best guess
is I had one VR241 on my desk. I certainly used the Rainbow VT220 mode
to talk to the SWS VAX for email, printing etc. Yes that's right email
in 1983! DEC had a system called AllInOne or DECmail and IBM's system
was called PROFS.
There were standard DEC cables for the one/two monitor configuration.
However I can make up cables from a diagram if needed.
Thanks and Regards
Rod Smallwood
(Now seeking any DEC RGB monitor current between 1982 and 1990)
-----Original Message-----
From: cctech-bounces at
classiccmp.org
[mailto:cctech-bounces at
classiccmp.org] On Behalf Of Tony Duell
Sent: 15 August 2007 22:43
To: cctalk at
classiccmp.org
Subject: Re: DEC Rainbow 100+ Plus
So phaseII is to locate a VR241 which is the 13"
RGB colour monitor
that would have been used with the Rainbow when it was current
equipment. The Rainbow is specified to work with both monitors
attached.
YEs, you can use both the mono and colour monitors on the 'bow, but you
need a special cable (and specialk programming?)
Let me explain.
The colour video card outputs _4_ video signals, which I call R, G, B,
Mono. The 'Mono' signal is mixed with the text video from the 'VT100'
circuit on the 'bow mainboard. This is the composite video signal that's
sent to the VR201 (yes, you can use a mono monitor with the graphics
card)
The standard colour monitor is a sync-on-green TV rate analogue colour
monitor. The standard cable connects it to R, Mono, B (to the R,G,B
inputs on the monito), the 'G' output of the colour card is not used.
This means you get green text from the mainboard circuit, and colour
graphics.
You can make a cable to connect a mono monitor to the 'mono' signal and
the colour monitor to the R,G,B signals. You then get the mainboard
video on the mono monitor only (along with grpahics, if you program the
CLUT correctly), and colour grpahics on the colour monitor.
I can send you details of the cabling if you want it
Be warend that the real VR241 is a horrbile thing. It's actually a
Hitachi chassis, complete with the well-known thick-film circuit in the
vertical deflection stage. The PSU is plain crazy, the chopper is driven
(indirectly) by a windign on the flyback (line output) transformer. So
for the PSU to run, the horizontal deflection circuit has to be working
properly. To get it started, there's an astable multivibrator o nthe PSU
board that is disabled shortly after power-up, but which gets the
chopper going for long nwnough that the delfection circuits can rattle
into life.
Debugging one of thise is 'fun' for suitable values of 'fun'. Just about
all the likely-bits-to-fail have to be working before it'll do anything
at all...
-tony