how do I connect a BBC micro to a VGA monitor?

From: Tony Duell <>
Date: Sun Feb 1 11:37:16 2004

> As a side note, any suggestions on how to convert CGA to analog RGB so I
> can run my Tandy 1000 through it?

Well, what you need to do is use some buffers and resistors to combine
the RGBI digital signals into 3 analogue signals (look at the schematics
of a CGA monitor for detials). If you don't mind just having 8 colours,
you can ignore the I signal, and just use potential dividers to reduce
the TTL signals to the 1V analogue levels (a quick-n-dirty solution if
the analogue inputs are terminated with 75 ohms, as they should be, is
just to put a 300 ohm resistor in series with each of the 3 digital signals).

Then you have to sort out the syncs. Typically you need to Xor the 2
syncs on the CGA connector to get a composite sync. Then maybe invert
that. Maybe bring that down to 1V levels with a 300 ohm series resistor.

Received on Sun Feb 01 2004 - 11:37:16 GMT

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:36:41 BST