From:	SMTP%"jenkinsj@flotsm.ozy.dec.com"  5-FEB-1995 10:51:31.02
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CC:	
Subj:	Re: DEC Monitor refresh rates?

From: jenkinsj@flotsm.ozy.dec.com (Jon Jenkins)
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Subject: Re: DEC Monitor refresh rates?
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Date: 4 Feb 1995 11:08:15 GMT
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Matt Thomas (thomas@lkg.dec.com) wrote:

: In article <3giqo3$f9m@crl.crl.com>, cgi@crl.com (Paul Smith) writes:
: |>
: |>We have 4 DEC Alpha and VAX boxes that came with 19" --> 21" trinitron
: |>monitors with 3 BNC connectors.  Does anybody know the Resolution and
: |>refresh rates for these monitors?  
: |>
: |>I.E. Horizontial= XXX Hz
: |>     Vertical   = XXX Hz
: |>     1280x1024 pixels at 80Hz refresh
: |>
: |>...
: |>
: |>My hope is to learn enough about these monitors to hook one of them up to
: |>a PC VGA controller??

: None of those monitor or multi-sync and none of them are VGA compatible.

: They will use one of these three values:

: Resolution	Vertical (hz)	Horiz. (Khz)	Bandwidth (Mhz)

: "1024x864"         72.03	   57.38	    74.30
: "1280x1024"        66.51	   70.70	   119.84
: "1280x1024"        72.56	   77.17	   130.8

: And sync is always on green.
: -- 
: Matt Thomas                          Internet:   thomas@lkg.dec.com
: U*X Networking                       WWW URL:    http://ftp.dec.com/%7Ethomas/
: Digital Equipment Corporation        Disclaimer: This message reflects my
: Littleton, MA                                    own warped views, etc.

Matt is correct that these are not multisync monitors but if you have a decent video
card that lets you set up refresh rates then you can build a simple circuit
that does the following:

PC VGA (15pin D)		Workstation 3xBNC
R	}
G	}      ------------	}R
B	}------| black box |----}G+VSYNC+HSYNC (0-0.3v=sync, 0.3-1.0=green)
VSYNC	}      ------------     }B
HSYNC	}

and the monitors PLL will have enough range to sync up OK.

Circuit is as follows (be careful with wire/PCB track lengths
and you will need to run the red an blue signals through
unity gain opamps to keep propagation delays the same)


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From: Brian Campanotti <bcampano@io.org>
Message-Id: <199410131626.MAA29074@r-node.io.org>
Subject: Re: Video SYNC Signals...HELP!
To: jenkinsj@ozy.dec.com (Jon Jenkins)
Date: Thu, 13 Oct 1994 12:26:38 -0400 (EDT)
In-Reply-To: <9410131152.AA11072@oils.ozy.dec.com> from "Jon Jenkins" at Oct 13, 94 09:52:21 pm
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>Hi Brian,

Hello...

>Do you know if there is a chip that will do the opposite:
>i.e. RED   }
>     BLUE  }           }RED
>     GREEN }  LM?????  }BLUE
>     HSYNC }           }GREEN (+vsync+hsync)
>    VSYNC }

>I have looked at this with passive componnents but the voltages
>were just too low to work i.e. green signal 0.3-1.0 and anything
>below 0.3 is considered sync.

Well, even though the voltage levels are low, they are perfect for
video...

I need to ask if the Hsync and Vsync are at logic levels (0-5V).
If they are, then you can pump them through a regular OR gate
(or NOR depending on the polarity of the pulses) and this will
give you COMPOSITE Sync (Hsync+Vsync).

Now, all that is left is to attenuate this 0-5V signal to the 
appropriate 0-0.3V level.  This can be done with a single 
transistor amp circuit (emitter follower, etc.) or you can
use a standard OPAMP with gain such that output amplitude is
0.3Vpp.  This is a circuit that I had suggested to someone
else for a similar application.  You may be able to draw 
some ideas from it...

Since the sync exits in "sync" with the R, G, and B
signals, all it takes is to combine this sync output with 
your G channel.  I guess this part depends on your electronics
knowledge, but all you basically have to do is the following:

(excuse the ASCII Graphics...)

						|\
Green -----\/\/\/-------------------------------|+\
  |	     R1	   				|  \
(0.3-1.0Vpp)					|   \
This signal may have to 		OPAMP 1	|    \     | |
be biased to 0.3V if the			|    /--+--| |--G+sync
green signal that you have			|   /   |  | |
is clamped to ground.		   +-/\/\/\--+--|- /    |
Use a resistor divider             |	R2   |	| /     |
after R1 set for 0.3Vdc            |	     |	|/      |
                                   |	     |          |
                                   |	     +---\/\/\/-+
                                   |		   R3
                                   |
                                   |
			|\         |
	   +---/\/\/\---|+\        |
	   |	 R4	|  \       |
 	 -----		|   \	   |
	  ---		|    \     |
	   -	OPAMP 2	|    /--+--+
			|   /   |  
Csync --\/\/\/---+------|- /    |
	  R5	 |	| /     |
		 |	|/      |
		 |	        |
	 	 +---/\/\/\-----+
			R6

Now, the Green and the Csync may need to be terminated with
a 75ohm resistor to ground at the input to this circuit, but
you can experiment with this.  The basic theory behind this
circuit is to combine the sync and the green 
using VIDEO OPAMP 1 (Video because you need the bandwidth).
and OPAMP 2 can be almost any OPAMP (I would use the same one as
you used for OPAMP 1 since you will get sharper edges on the sync
signal) this is where you can attenuate the 0-5Vpp Comp Sync signal.

The Green signal is connected to the non-inverting input, but the
sync is a little tricky.  Since it is going into the inverting
input, it must first be inverted (negative pulses -> positive
pulses -> OPAMP = negative pulses) then attenuated (some sort
of gain stage).  Now, I don't know what the signal levels
you are dealing with, but by playing around with the resistors
you have to get the sync to 0.3Vpp (Volts peak to peak) and
the Green to 0.7Vpp (DC biased at 0.3Vdc) and this would indicate
that the output (G+sync) should be 1.0Vpp after they are combined
at the output of OPAMP 1.

What I would suggest is to use pots for R1, R3, and R6, and
pick fixed values for the remaining resistors.

Remember:	Non-inverting OPAMP gain = 1 + R3/R2

		Inverting OPAMP gain     = -R6/R5

You may even find that you get better results by omitting
R1 and R4.


>Thanks jon

No problem...
Brian

bcampano@io.org
Toronto, Ontario, Canada


--
----------------------------------------------------------------------
Name:        Dr Jon Jenkins
Location:    Digital Equipment Corp, NaC, 
             Burnett Place, Research Park, 
             Bond University, Gold Coast
             QLD, AUSTRALIA 4229
Phone:       61-75-75-0151
Fax:         61-75-75-0100
Internet:    jenkinsj@ozy.dec.com

The opinions expressed above are entirely personal and do not
reflect the corporate policy of DEC or the opinions of DEC management.
-----------------------------------------------------------------------
