Conference 7.286::atarist

    
    I don't know the VR262, but if it has a video input (it's mono as
    you said) then you may run the Atari in one of the two color modes
    and compose a mono video signal out of RGB and sync from the 
    monitor interface with one transistor and some resistors.
    
    But, that works only if the monitor has a standard mono video input
    and you are in Atari's color mode. I'll post the schematic for a
    RGB+Sync-to-Monovideo here next week (if I find them in my mess).
    
    Bernd
    

Check PRNSYS::USER2:[LOMICKAJ.HOBBY.ST]MONITOR.TXT for VT240
instructions, to see if that is applicable.  I don't know what a VT262
is either.

VR262 -- isn't that the mono screen for a workstation?

Chad

    No ! a VR260 or VR262 will not work on a Atari System ,
    because the operating Horizontal Frequency on a VR must be higher.
    
    The mono atari screen is working on a frequency approx. 24kHz.
    The freq. on a color screen is 15625 Hz (germany).
    
    And !! the hor. freq. for the VR262 is more than 50KHz.
    to get the high resolution output displayed.
    
    but, i think if you by a graphic expander module ,
    the price is about 1700.- DM (to expencive) it will work.
    
    try it   joerg
    

Although it seems that the monitor won't work anyway, here is the
promised schematic fo how to connect a normal mono-monitor with
video-input:


Create a composite sync signal out of Hsync and Vsync (early 520STs didn't
have composite sync)
       
                                  o 5V
5V      10k Ohm                   |
o-------/\/\/\/\/\----|           |
                      |          /
Hsync     1N914       |        |/C
o---------|<|---------X--------|    NPN-Trans. 2N3904
                      |      B |\E
Vsync     1N914       |          \        100 Ohm
o---------|<|---------|           X------/\/\/\/\--------o Composite Sync
                                  |
                                  |       160 Ohm
                                  |------/\/\/\/\-------|
                                                        |
                                                       ---  GND


Now how to mix RED/GREEN/BLUE and COMP.-Sync to a mono video signal:


            
Comp.Sync       47 Ohm
o-------------/\/\/\/\/\------------|
                                    |
Green          120 Ohm              |
o-------------/\/\/\/\/\------------X
                                    |
Red            270 Ohm              |                 Mono Video
o-------------/\/\/\/\/\------------X------------------------->
                                    |
Blue           820 Ohm              |
o-------------/\/\/\/\/\------------|


I didn't double-check if Jeff posted this also in his topic on how to 
connect other monitors, if so I'm sorry to waste diskspace for an already
known subject.

Bernd

    Hi,
    	RE: .5   Will this produce a colour composite video as well?
    I could then use it to drive a modulator (I have a Mega ST2).
    
    	Thanks 
    
    		Roger

    
    
    The drawn circuit only produces a mono video. If you want to have
    color video out of the RGB-signals of your Atari you need to have
    a RGB-to-Video converter. This is a bit more hardware, all in the
    middle a certain Motorola chip exactly for that purpose. Count
    about 20.- to 30.-$ for parts if you heat up your soldering iron
    and do it on your own. The subject was discussed in this and the
    electro hobby conference. If you're really interessted to do it,
    I could send you a copy of the schematics.
    
    Bernd
    
    P.S. the circuit shown in Re.-2 works only in the two color modes
    of the Atari but produces a mono output to connect a cheap general
    amber or green (or whatever color it is) monitor with video input.
    

Re: .6

Practical Solutions makes "Video Key" which will probably be cheaper and
more accurate than anything you can build, unless you are into analog h/w
design with a strong video background.

							-Dave

    RE.7
    
    	Yes please! My snail-mail address is Roger Lane @BIO-9.

    			Thanks
    
    RE.8 
    
    	Where can I find details of this? (I'm in the U.K)

    
    			Thanks Again
    
    
    		Roger

Sorry, I didn't realize you were in the U.K.  "Video Key" is an NTSC solution,
I don't think it does PAL, which is probably what you are looking for.  I will
try to remember to enter some of the specs, if you are still interested.
I believe Video Key sell for around $69 US.

							-Dave

    Hi,
    there is an equivalent UK product I have seen advertised in the mags, I
    will dig out the advert and post it here!
    
    Pat K.