🚀 go-pugleaf

On 26 Jun 89 07:56:26 PDT (Monday), "chaz_heritage.WGC1RX"@Xerox.COM
wrote:
>
>
>Has anyone succeeded in deriving from the ST's RGB output an RGB drive
>suitable for a SCART-input Trinitron? I'm told that the digital RGB from
>the ST has to be attenuated - presumably from 5V to 1V - to match the
>Trinitron's analogue RGB input. However, before getting the soldering iron
>and resistors out I'd be interested to know if anyone else has done this,
>and preferably what values of resistors they used.

You have been partially misinformed.   The RGB output from the ST is analog.
The RGB level is fairly conventional: 1V positive into 75 Ohm.  This is
compatible with most analog input to multisync monitors.  The horizontal and
vertical sync outputs on the other hand are TTL.  These lines might be the
ones that need to be attenuated if SCART requires 1V syncs.  In this case
an attenuator (voltage divider) is easy to build.  For example:

ST Sync      _____________
(H or V)                 :
                        ___
                        : :   R1
                        ---
                         :
                         :____________ SCART sync input
                         :
                        ___
                        : :  R2
                        ___
                         :
                         :
                       ______
                       /////    Ground

where the resitors R1 and R1 are chosen such that: (R1+R2)/R2 = 5.
A reasonable value for R1+R2 would be larger than 2.2KOhm.


>The ST-SCART cables sold by many computer stores work fine on other
>monitors - the more honest stores say 'Not for Sony'; Computer Express say
>that it'll work, and then refuse to have anything to do with you when it
>doesn't...

What is SCART?  What are the specs?

Marcelino Bernardo
bernardo@erevax.bitnet  (Please ignore the address above. Use this instead)