This project describes ways to get an improved quality picture from the Amstrad CPC (classic not plus) on a modern LCD or Plasma TV. After recently reading an article, that stated that the well-known CPC SCART cables don't work on Modern LCD / plasma TVs, I decided that I would investigate alternative options, because I was about to dump my last CRT for a plasma TV. I should mention at this stage, that the solution here, will not quite give you the same quality as a SCART cable on a CRT, but it is considerably better than the picture achieved by an [[Amstrad MP1/MP2 modulator|MP1/2]] setup and is very close to the SCART solution. With further improvements a SCART quality picture is possible using this method, but I will go into those details further down.
This articles describes Composite video options. If you are looking for RGB options, have a look at "[[LCD monitor and LCD TV Solution (RGB)]]".
== Warning / Disclaimer ==
This project involves opening and modifying a device which uses 240V AC. If you don't know what you're doing, then leave it to someone who does. Although the modifications do not involve the high-voltage areas of the circuit, extreme caution should be taken at all times and the unit should always be disconnected from the mains supply BEFORE the casing is opened and only re-connected after the case has been closed again.
Although I have taken the utmost care preparing this documentation, I do not guarantee that it is error free and I accept no responsibility for damage to anyone’s MP1/2, shiny new television, other personal equipment or injury inflicted on you or others.
Using a short length of coaxial cable, we need to tap off the composite signal at the two points shown in the picture above. The outer shield of the coax cable should be twisted tightly and pre-tinned with solder beforehand, to ensure that no stray strands of the shield cause a short circuit. The shield is soldered to the earth track or the RF casing (Point A). The centre core of the coax is then soldered to the composite output of the circuit (Point B). Next we need to mount a female cinch socket. You can either use an inline connector which can be mounted on a fly-lead outside the casing or a surface mounted cinch socket which is mounted directly in the casing. I chose a surface mounted socket, because I find the solution neater, but you may prefer the fly-lead solution with female inline connector or an even longer fly-lead with a male cinch connector for direct connection to the TV. It's up to you. If you are using a surface mounted socket, it is also possible to use two normal wires to make the connection, but you should twist these around each other to avoid interference. When drilling holes in this type of plastic, a wood drill-bit should be used on a slow speed so that the plastic doesn't crack or melt in the process. Once you have made the connection to the connector / socket, carefully return the circuit board to its original position and replace the three mounting screws. Fortunately the circuit board is mounted at a slight angle, which means there's plenty of room for the additional connections. Make sure the new composite circuits are routed well away from the power circuitry and the transformer on the right, as a short circuit between these circuits would not only cost you your MP1/2 but most likely destroy your shiny new plasma TV along with it.
== Building Your Own RGB To Composite Converter ==
''Note:
An updated circuit that only requires 5V can be found here:'' [[RGB_SVideo|RGB SVideo]]
If you are not lucky enough to have an MP1/2 lying around at home, then you'll have to build your own. This circuit won't supply your CPC with the 5V or 12V it requires (A SCART cable doesn't either), it just converts the RGB to Composite. The circuit below is based on the Motorola MC1377 RGB to PAL/NTSC Encoder. It is almost identical to that found in an MP1/2 and is more or less the same as the application example found in the datasheet for the Motorola MC1377 with a few small changes made to reduce manufacturing costs. Almost everything that needs to be done is taken care of by the MC1377 with just a few external components to adjust the signal levels correctly and produce the frequency required, etc.
[[File:MP2_PCB_Tracks.pdf]] - PCB Track Layout)
[[File:MP2_PCB_Layout.pdf]] - Component positions
If you find an alternative delay line (in an old TV perhaps), make sure that it is a high impedance part (1 - 1.5K) otherwise your circuit wont survive very long. You will also have to adjust the values of R8 and R13 to suit the impedance of the particular delay line you intend to use. I was unable to source either of these parts, so until I find another solution, I will have to live with jagged edges.
The MC1377 is a rather dated component. Since then, newer and better ICs have been developed which produce a much better picture quality. The schematics for a converter based on the AD724 can be found here: [[RGB_SVideo|AD724 Based Converter]]
If you have any further questions regarding this project, please contact me through the Wiki Forum.
== More Modern Solution ==
The MC1377 used in the circuits above is a rather old IC and is getting quite difficult to find these days. A more modern IC, the AD724 is now available and produces a better composite picture and even an S-Video output which gives a considerably better picture than a composite signal. Instructions on how to build an AD724 based modulator can be found [[RGB_SVideo|here]].
Bryce.
[[Category:Hardware]] [[Category:Peripherals]] [[Category:DIY]][[Category:Graphic]]