want to buy EGA board, new or used

[robert.s.sklar]

In article <936 at gvgspd.GVG.TEK.COM>, mrk at gvgspd.GVG.TEK.COM (Michael R. Kesti) writes:
> In article <46407 at sgi.sgi.com> gsk at khaki.sgi.com (George S. Kong) writes:
> >i would like to buy a STB Multires II board, or a Taxan 557 GOLD Card,
> >or some other EGA board that is capable of driving an AT&T 318 monitor
> 
> Is this really possible, I mean running an EGA card with the 318?  I
> know how to disable the built in display adapter, but what has always
> kept me from upgrading was the cost of a new CRT.  I have a 318/T
> monitor.  Can I install one of these cards and get EGA?
> 
> This inquiring mind would like to know!
> 
> -- 
> ============================================================================
> Michael Kesti  Grass Valley Group, Inc. | "Like one and one don't make two,
>     mrk at gvgspd.GVG.TEK.COM              |  one and one make one."
>     !tektronix!gvgpsa!gvgspd!mrk        |         - The Who, Bargain

     Yes, it is possible to use AT&T 318 and 319 monitors as EGA monitors.
AT&T supports this with the 750 video controller.  Prior to the introduction
of the 750, AT&T recommended (I am not sure if this was official) the STB
Multires II EGA board mentioned above.  

     Using the STB or other board capable of operating at 25 KHz and using 
a standard DB9 connector requires the use of a DB9 to DB25 adapter.  Of 
course, the AT&T 750 board has the AT&T standard DB25 video connector.  It 
also has a connector on the board for the 15V power supply required by the 
AT&T monochrome monitors.  All that is needed is to move the 15V power 
cable connected to the built-in video card in the 63xx.

     When installing a different video card in an AT&T PC63xx with a built-
in video controller, it is necessary to disable the built-in card.  Some of
the later cards have a jumper that can be moved to disable the card.  Early
cards can be disabled by replacing one of two chips with an appropriately
wired header plug.

     For those interested in an inexpensive 25KHz color monitor for use
with an AT&T PC, a Roland CD240 can be used with a simple *active* adaptor
or adaptor cable.  I think that this monitor is still available from
California Digital for about $220.00.  It is a very nice monitor (I own
one, and a close friend owns one) whos only drawbacks are that it is not
super bright and that it needs the adaptor.

     The adaptor required for the Roland CD240 must invert the horizontal
and vertical sync signals.  This is easily done with a 74LS04, which can
be powered by a 78L05 miniature (~100mA) voltage regulator that is fed by 
the +15V pins on the DB25 video connector.  This adaptor also takes care
of the DB9 to DB25 conversion.  If the Roland is used with an STB Multires 
II, the invertors are not needed, as the STB has options to take care of 
this.

				Robert S. Sklar
				AT&T Bell Laboratories
				Naperville, Illinois
				(312) 979-4323
				att!ihlpl!sklar