20 Jul
1999
20 Jul
'99
8:15 a.m.
Having had a whileto recall, I believe the SONY, formerly attached to a SUN,
did, indeed, have five BNC inputs on it. However, in order to get the
display board and the monitor to "play" together, it was easier to use only
three of them because, in the absence of SYNC on the last two BNC's it
happily responded to negative-going sync on GREEN. I'm not sure whether
there was a switch to enable this function. The monitor on the floor next
to me has such a switch and I was using it up until a few weeks ago, and for
seven or eight years, so it's likely I'll occasionally confuse it with my
SONY experience. The one on the floor is a multisync-capable Hitachi with
both the DE15 and the 5 BNC's on it with a switch to select which it uses.
All the points you've made are well considered, which is why I suggested you
start with the resistor to green just to see whether you can use this
monitor with the cards you own. It's really not worth the effort to make a
card not already capable of the right scan rates do the job if you have to
reinvent the display board's BIOS, as that vendor in southern California
does. At 50 cents per hour, the effort will approach the national debt. A
really decent 19" monitor compatible with most any current VGA card costs
$400 at the Best-Buy or whatever other discount store you like. There is a
point beyond which even I, frugal as I am, won't wander.
I'd advise you to find a card which looks like it works at a non-interlaced
60Hz vertical and approximately 64kHz horizontal sweep and negative going
sync. If it has the rate but not the polarity, don't fiddle with the
firmware, just attach the resistor as I suggested and see what you get on
the display. If that works, then maybe you should build an adapter which
serves more appropriately and safely for the long run. (The resistor never
impressed me as particularly good for the display board.) You can easily
build a perfectly solid adapter using a CA3127 or equivalent HF transistor
array and a few resistors which will adapt your display board capable of a
suitable sweep rate to "WINDOWS-compatible" sweep rates. If you want more
than that, perhaps you're beating a dead horse.
Dick
-----Original Message-----
From: Lawrence Walker <lwalker(a)mail.interlog.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Tuesday, July 20, 1999 5:26 AM
Subject: Re: Sun Monitor (UK) (2)
On 19 Jul 99 at 18:48, Richard Erlacher wrote:
What I meant was that IF your monitor has only three
BNC's, as my formerly
SUN SONY GDM1950 19" monitor did, then you need to impose negative-going
composite sync on the GREEN Video output of your VGA/XGA card. IF your
monitor has five BNC's on the back, then any reasonably close to 60Hz
vertical and 64kHz horizontal sweep rate will probably work fine.
Unfortunately, since these are fixed frequency monitors with a VERY fine
pitch and a VERY linear sweep and a VERY easy-to-converge system, one
price
you pay is that you can only use them at the ONE sweep
rate for which they
were designed or close to it.
If you have the five BNC's, then you need an adapter cable which has the
HD
DE15 connector at one end and, guess what, the five
BNC's emanating from
it.
These should have RED, GREEN, and BLUE, with the
respective returns on
each
75-ohm coax, and HSYNC and VSYNC, negative-going from
ground, by the way,
but that may not matter as they're AC coupled at the monitor.
Since you can buy the adapter for about $20 here in the US, I doubt
they're
much different there in the UK. In any case,
you've avoided any soldering
other than at the cable if you build it yourself.
I use a 5 BNC to VGA adaptor with my NEC now so that's no problem.
The Sony GDM1950 designation is strange. Yours was a Sun, mine is a SuperMac
and in searching the net I also found references to a Radius version, whom I
had thought manufactured their own monitors. There seem to be 19-21"
versions
and now I find also 3 and 5 BNC editions. Makes finding specs difficult. I
found this reference in the Sync on green FAQ :
"For example, a STORM 1280/256 will drive a Sony GDM-1950 at 640x480,
800x600,
1024x768, 1280x1024 and DOS modes (this monitor is rated at 63.34Khz
Horizontal
sync. and the card runs at 64Khz Horizontal sync.). This card uses an S3
graphics accelerator. See also PC Magazine/April/13/1993."
Now what kind of bloody "fixed frequency" is this. On another site ISTR they
even had a different scan rate.
If you need a circuit suitable for the three BNC
arrangement, I actually
have a really solid one using an HF transistor array and a negative
supply,
which, by the way, is on the motherboard, so neatly
attaching it to the
video card isn't too unrealistic. For just checking it out, I'd suggest
the
500-ohm resistor, though, provided you can find an
application (that's the
formerly edge-connector at the top of the VGA cards of yesteryear. They
had
16 pins as do the current pin fields, so you'll
find from old doc's which
one's the composite blanking.) connector somewhere.
Ah, now I see what your referring to. Usually called a "feature" connector
by
IBM.
If the monitor has all the signals entering via the 5
BNC's you just need
to
fiddle with the VGA card's operating mode to get
it into a 60Hz
non-interlaced mode. Many of the newer VGA's won't do this, so read the
spec's carefully! The older ones which did produce the high frequency dot
clock required were expensive, and the newer ones don't have fast enough
DAC's to do the job, so shop carefully, and make sure you can return the
board if you buy one. IT MUST BE CAPABLE OF 1280 x 1024 lines at 60Hz
without interlace!
Good Luck!
Dick
I'll likely bite the bullet and just try it on the old MCA ATI MACH 32 card
(which also has the "feature" connector BTW) in my PS2 8580 after seeing
what
info I can pry out of ATI who are based here in Toronto.
Thanks.
ciao larry
lwalker(a)interlog.com
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