Difference between revisions of "TV SCART cable"

Revision as of 17:02, 19 December 2010

A TV SCART cable allows to connect the CPC/CPCplus to the TV set. This is especially helpful if you couldn't get your hands on a colour monitor or want to use the CPC/CPCplus as a video console in the living room.

Schematics

Amstrad/Schneider CPC (classic)

Colour Picture (RGB)

This schematic requires a TV with RGB input on Scart Connector (back in the 8bit era, many TVs have had only Composite input implemented on Scart connectors - nowadays RGB is also supported by DVD players and 3D gaming consoles, which is possibly increasing the chance to find RGB support on modern TVs).

The 9V and 1.5V batteries are optional. They may be helpful to switch the TV to RGB mode automatically, without needing to activate it via buttons on the remote control. Instead of the batteries, you may also extract the voltages from elsewhere (like the CPC supply), valid are Pin8 = 9.5V - 12V (9V is actually a bit too low), and Pin16 = 1V - 3V.

Schematic for a CPC classic connection to a TV-set (Colour Picture) Note: The left and right sound channels are swapped in this diagram

Black & White Monochrome Picture

This schematic passes Luminance to the TVs Composite Input. It's giving only a monochrome picture, the advantage is that it works on nearly all TVs including such without RGB input.

Doing this would be useful only for using the TV as replacement for the GT64/GT65 monitor.

Bug: The 1.5V battery shown in the mono schematic is nonsense; for composite, Pin16 should be wired to GND, not to 1.5V.

Schematic for a CPCclassic connection to a TV-set (Black & White Picture) Note: The left and right sound channels are swapped in this diagram

Alternative RGB Wiring

Schematic to connect to RGB without requiring a 1.5V supply (Colour Picture) The 9V supply (as shown above) may still be required if the TV-Set has no AV Source Selector. If you experience picture flickering or the TV OSD appears intermittently while the CPC is connected, add a 100µf capacitor (optional) as shown above, this should resolve these problems.

Amstrad CPCplus (In theory also GX4000, but it has its own SCART outlet)

Colour Picture (RGB)

Schematic for a CPCplus connection to a TV-set (Colour Picture)

Black & White Monochrome Picture

Schematic for a CPCplus connection to a TV-set (Black & White Picture)

Additional Resistors

Info from OCT: "I recall that when Amstrad Action came up with the proposal for a SCART cable back in issue AA41, numerous readers wrote in suggesting that resistors (most commonly: slightly below 330 ohms) should be connected "in series to the colour signals [...] for improving picture quality" (AA45, June 1989, FORUM, p. 23), so they seem to have appeared overblown in comparison to the CTM644s' back in the day."

The goal of that improvement is unknown - it might alter the medium-to-bright ratio, or, it might be simply intended to reduce the overall brightness (such like when the CPC picture appears brighter then normal TV programs). The voltage/brightness output by the CPC is actually higher than normal SCART voltages, however, the voltage drops when the TV applies load to the RGB pins; that load may vary from TV to TV, and so, the resistors may be needed only on some TVs, but not on others.

Videos

A SCART cable howto:

{{#ev:youtube|yNT36Tf6PxU|300}}

See also

• Connector:Monitor - Video output on the CPC