Using a Samsung LE19R71BX 19" LCD Television with an Atari ST - v1.00.

1. Introduction.
2. The Samsung LE19R71BX.
3. Atari Video Syncronisation Requirements.
4. How does the LE19R71BX perform?
5. How is the cable wired?
6. Level adjusting resistors.
7. References.

1. Introduction.
The aim here is to have a single display for all of the ST's resolution modes, low, medium, and high.  Historically this has only been achievable with multisync monitors.  These are traditionally VGA monitors which will sync down to 15Khz.

2. The Samsung LE19R71BX.
This is an LCD television accepting inputs from SCART (RGB and AV), VGA, and AV (Composite Video, L+R Audio) inputs.  UHF/VHF terrestrial broadcasts can also be received.  It is one of the new breed of televisions which also allow a VGA input.

3. Atari Video Syncronisation Requirements.
                                low     medium  high
                                ------- ------- -------
Horizontal Frequency:           15.8kHz 31.5kHz 35.7kHz
Vertical Frequency:             60Hz    60Hz    71.2kHz
Horizontal Resolution:           320     640     640
Vertical Resolution:             200     200     400
Signal level:                    ---     ---     ---
(analog)                            1.0Vpp 75 ohm
Sync Signal level:                  TTL 3.3K neg
(analog)                         ---     ---     ---

4. How does the LE19R71BX perform?
The VGA mode is scaled to fit the screen.  It is almost pin sharp considering that the ST's high resolution is 640x400 pixels.  The SCART (RGB) mode used with the low and medium resolutions can suffer from what could be described as digital processing artifacts.  These however are barely noticable and only an issue if you choose to focus on them.  There are LCD televisions which are known not to display any output from the ST at all.

5. How is the cable wired?
The audio from the Atari ST is fed to both the SCART (RGB) socket and the PC/VGA input ports.  The Atari's monochrome signal is fed to R-G-B on the VGA input.  The Atari's RGB signals are fed to the SCART socket.

A simple toggle switch controls the ST's monochrome detect signal.  At which point the relevant selection is made on the television to select either SCART or PC mode.  It is as simple as that.

The only point of note is that you will have to have an output cable from the ST which has 11-cores.  And which is not excessive in diameter so that it cannot be crimped with the 13-pin plug.  A fully wired 20-core SCART cable is not suitable, and a partially wired 9-core SCART cable does not have enough cores.

6. Level Adjusting Resistors.
These are not included.  It was noted that by using them that slight ghosting or a halo effect was seen.  If the display is too bright, turn the brightness down.  Standard SCART inputs are 0.7vpp.  The ST's output is 1vpp.

7. References.