Use the Spectrum 128 style menu below to navigate to the various sections detailing the SCART cable.
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| Testing The Lead |
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The lead I constructed houses all of the circuitry in the SCART plug and is shown below. The audio signal from the MIC socket is taken into the DIN plug and simply routed down the cable to the SCART plug. For best results, the audio signal should ideally be separately screened within the cable to minimise cross talk with the video signals, but in practise this is not really necessary.
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The Spectrum 128 can display a test screen that is intended to assist tuning in a TV set. The test screen is accessed by holding down the BREAK key whilst resetting the Spectrum 128. The test screen consists of a series of vertical lines showing each of the shades of colour available from the Spectrum, with a one second 440Hz tone produced every other second. A screenshot of the test screen is shown below.
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The code for the test screen is contained at the end of the '48K BASIC' ROM in previously unused locations. A commented disassembly of the routine is available here for viewing. The file is stored in PDF format and hence Adobe Acrobat Reader is required.
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Click here to view the ROM disassembly of the Spectrum 128's test screen routine. |
Full disassemblies of the Spectrum 128 ROMs, along with disassemblies of the Spectrum +2 ROMs, and Spanish Spectrum 128 ROMs are also available.
The photographs below show the relative clarity of the TV display when using the aerial lead, the composite video connection and the RGB connection.
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| Aerial | Composite Video | RGB |
