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.
===========================================
Atari
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.
==============
http://www.hughesdirect.co.uk/showproduct.php?cda=showproduct&pid=SAM-LE19R71WX
http://www.preromanbritain.com/gwem/martbean/ataridiy/nexmsync.htm
http://www.howell1964.freeserve.co.uk/Atari/ST/Atari_ST_Video.htm
http://www.algonet.se/~guld1/hardware/atari-scart.html
http://www.volny.cz/milarb/Atari/specable.txt
http://www.notator.org/contributions/st_vga.zip
http://pinouts.ru/Video/VGA15_pinout.shtml