The first thing I tried was using the Intensity line to pull-up the voltage of R, G, and B when I is +5V. You could probably use smaller (1/8 Watt) resistors. Note: in all of my circuits I used 1/4 Watt resistors and 1N914 diodes (equivalent 4148 diodes). You can judge for yourself which you like best and might want to try building yourself. I built four different circuits and got some screen shots for each. It's easy to imagine using the Intensity output of the C128 to scale the R, G, and B outputs before going into the converter to get a true RGBI conversion - and thus all 16 colors. Indeed, many of these boards have small pots (variable resistors) that can be used to scale the voltages on the R, G, and B inputs. The input to a typical RGB to S-Video converter is analog. When the I line is low, the transistors would still pass some current because they're slightly biased "on." By the way, RGBI output of the C128 is TTL Level (0V or +5V) unlike VGA which uses analog voltages around +1V. When the I line goes high, those transistors would amplify the R, G, and B signals producing a brighter color.
#COMPOSITE VIDEO TO VGA CONVERTER SCHEMATIC SERIES#
A typical RGBI monitor would have a transistor in series with each of the R, G, and B lines.
Examples: 2 shades of Red, 2 shades of Green, and 2 shades of yellow (Red+Green). The Intensity output is designed to make whatever primary color(s) is(are) currently active (Red, Green, and/or Blue) appear brighter. With one of these boards, a DC power supply, and some wiring, you get a nice color output compatible with many video displays. These are not too dificult to find and shipping is cheap. Because of this many programs are unpleasant or completely unusable!Ī better solution, costing less than US $50, is an RGB to S-Video/Composite converter board. On my TV, white and gray appear almost identical. As you might guess from the name "monochrome," there is no color! Only three shades of gray: white, gray, and black. You build a simple cable (or buy one) to connect this monochrome output to the Composite or S-Video input of many video displays. One solution built into the C128 by it's engineers is a monochrome output. RGBI is similar to VGA, but uses different voltages and horizontal frequency which most VGA monitors do not like (alternative options are VGA and SCART). This poses a problem for C128 owners due to the dwindling supply (and expensive shipping) of RGBI and CGA monitors (CGA is very much like RGBI). Unfortunately, the RGBI output of the VDC is not compatible with modern equipment.
#COMPOSITE VIDEO TO VGA CONVERTER SCHEMATIC TV#
The VIC is easy to connect to common video displays (TVs and monitors) due to various widely-used outputs: Composite, Chroma/Luminance (S-Video), and RF (analog TV antenna). The VDC also supports video interlacing in hardware. It offers higher resolution than the 40-Column display of the VIC-IIe (8564 NTSC, 8566 PAL-B often called simply VIC). The Commodore 128 features an 80-Column color display using an RGBI output via the 8563 VDC.
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