Sun Monitor (UK) (2)

From: Lawrence Walker <>
Date: Tue Jul 20 02:15:25 1999

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

> 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.


ciao larry

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Received on Tue Jul 20 1999 - 02:15:25 BST

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