29 Jan
2013
29 Jan
'13
6:59 p.m.
On Tuesday (01/29/2013 at 09:02PM +0000), Tony Duell wrote:
Yes... although I've seen another reference that says it runs at 56KHz.
That could be wrong. I've not yet found the statement in the VT240
docs that says what the terminal actually sources...
OK. Thanks for the good advice. The VR241 that I acquired will need lots
of cleaning before it ever gets powered on. It looks like it has gone to
the bottom of the sea and back but I know that's not the case. I think it
was used in an auto parts or repair shop and it is one grimey piece currently.
However, I have just confirmed that two VT240 work with nice clean video on
another monitor so that is good news and very much worth the price ($0) :-)
Chris
--
Chris Elmquist
Are there any recomendations for a converter that can take RGB with
sync on GREEN as input and produce a VGA (or HDMI) output suitable for
driving a modern LCD?
Sivne you mention the VR241 later on, I guess yoy need to do scan rate
conversion too. The VR241 is TV rate (around 15kHz horizontal). Mos, if not all, LCD TVs sold over here have analogue
RGB inputs at TV
rates on the SCART socket(s). It's not sync-on-green, so you may have al
ittle fiddling aobut to do, but at least the inputs exist. I have alos
seen, but have no experience of, a SCART to HDMI interface unit. I assume
tht has analogue RGB inputs on the SCART connector.
Hmm... yes. You guys are spoiled with this SCART thing :-) SCART has
separate sync? RGBHV? Not hard to build a sync separator I suppose.
I'm thinking a guy could make a major project out of this and use three
high speed A/D ahead of some ARM based board that could acquire the video,
scale and convert to taste and then output on HDMI. Should be able to
handle lots of legacy analog formats that way.
On the other hand, I thought an existing something would be easier to
find maybe in the video game restoration world or other places where
RGB video was king.
A couple DEC
VT240 came my way this weekend and they will need some TLC to
restore but the VR240 that came along with them is in even worse shape.
I'll give it my best shot but ability to use an LCD as Plan B would
be nice.
Be warned that the VR241 is not easy to work on. The switch-mode power
supply is mostly on the live side of the isolation barrier and it is
driven by the horixontal oscillaotr (presuambly to prevent paterning from
the SPMSU osicilaltor nd horizotnal oscillator beating against each
other) via a winding o nthe flyback transofrmer which provides isolation
bnetwene mains and output sides. For startup there's a multivibrator
oscilaltor on the PSU board which is disabled when a capacitor shcages up.
Therefore, for the PSU to run, not only doe it have ot be workign
properly, but the horixotnal driver nad output stanges have to be workign
too. Not easy to trace fualts...
IIRC it's actually a Hitachi desing. Certianbly the thick-film module in
the midle of the scna PCB looks like a Hitachi product.