rbourass@udenva.UUCP (Mr. Photography) (05/17/87)
The following schematic was posted on the C-64 net by Frank Prindle
(prindle@nadc). It is not verbatim, but he should get credit for the drawing.
This schematic shows how to build a simple device to convert RGB signals to
a useable 16-tone grey scale for composite input on a monochrome monitor.
Any colours usually lost in a monochrome display are greatly enhanced through
this device. Something similar is sold commercially for about $40. This
cost me $9 made from parts at the local Radio Shack.
Hope it helps someone else...
RGB Color Port to Monochrome (Grey Scale) Composite
RGB (DB9)
Connector
---------
* 100 DIODE +5 Volts
Pin 3 R>---/\/\/\/--->|----+ v
| 680 |
* 220 DIODE | +--/\/\/\/--+
Pin 4 G>---/\/\/\/--->|----+ | |
| | 2N2222 |
* 300 DIODE | 100 100 | |-----+
Pin 5 B>---/\/\/\/--->|----+----/\/\/\/--+--/\/\/\/--+-----|
| | |->---+-------->
* 240 47 | | | Video
Pin 6 |>---/\/\/\/---------+----/\/\/\/--+ | +-----+ Out
| | | To
| 33 | | 82 Monitor
+----/\/\/\/--+ | +--/\/\/\/--+-->
| | |
v | v
(gnd) | (gnd)
2N2222 |
100 |-------------------------+
Pin 8 H>---/\/\/\/---------| |
|->---+ |
| | Note: + denotes a
v | connection; there
(gnd) | are no crossovers
2N2222 | in this schematic.
100 |-------------------------+
Pin 9 V>---/\/\/\/---------|
|->---+
|
v
(gnd)
Pin 1 >------------------------------+ Note: Carry both grounds through
| and tie both to ground to avoid
Pin 2 >------------------------------+ signal degradation.
|
v
(gnd)
* These four resistors determine the grey scale. They can be replaced with
500 ohm trim pots for experimentation.
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