An article by Stuart Mason.
8BS will not accept responsibility for
any damage that you may do to yourself
or your equipment whilst attempting to
carry out the following modifications
to monitor cables. If you are not
completely sure that you understand the
instructions, don't do it!
How to construct a cable to drive a CGA
/SGA/SVGA monitor from a BBC micro.
1. BNC connectors to BBC RGB 6 pin Din.
Using an old BNC video cable.
Viewed looking into the Din plug
towards the micro
Link pins 2 and 4 with insulated wire.
3
2 4 Sync A
1 5 Ground
BNC Din Plug
BNC
^
BNC 3 Screen Wires
(INSULATED)
Tools Required:
1. Soldering Iron.
2. Solder.
3. Wire Cutters.
4. Insulating Sleeve.
5. Insulating Tape.
BNC to 6 pin Din notes. With this type of cable there are 3 BNC
plugs which drive the video screen
represented by "RGB" on the back of the
monitor.
Take the old cable and cut it so that
you have the three BNC connectors and
at least three feet of cable. Carefully
remove 2.5 inches of the outer sleeving
from the cut end the cable.
Join the three outer earth screen
cables by twisting the wire together,
solder to secure. Then solder a short
piece of insulated wire to the end of
this wire.
Join the two pins 2 and 4 as shown with
a piece of insulated link wire. Now fit
insulation sleeving over the three
coloured wires and solder to the Din
plug as follows:
Red feed to pin 1.
Green feed to pin 2.
Blue feed to pin 3.
Pin 5 is the ground (earth). Solder the
insulated wire from the three joined
screen wires to this pin.
It is VERY important that none of the
wires short with any of the other
wires. Check that all bare wire is
insulated by plasic sleeving placed
over the wire before soldering or
insulation tape.
Because there are so many variations of
screens, you may have to try different
combinations of switch settings on the
monitor to get the picture right.
I've tried this cable and the more
popular 9 pin sinch connector cable
with various monitor screens such as
IBM XT and AT, NEC, Hitachi, Microvitec
and Panasonic. I have not tried it with
the Amstrad, so I am not sure how their
screens are driven.
These cables could be of use to someone
who has a large screen IBM/PC clone
monitor which can then be used with a
BBC micro. Because the PC monitors are
designed for higher graphics standards,
they do improve the quality of the BBC
display with respect to colour,
sharpness and better colour definition.
2. 9 Pin sinch connector to BBC RGB 6
Pin Din.
Some IBM PS monitors have a 9 pin
socket on the back. Labelled "TTL".
Usually these monitors are of the CGA
and EGA type.
Construct the BBC end of the cable as
follows using ordinary wire which seems
to work fine:
3
2 4 Sync A
1 5 Ground
Ensure that the wire is no longer than
one meter.
This is the same as method one (BNC to
6 pin Din), but without linking pins 2
and 4.
Then solder the wires to the 9 pin
sinch plug as follows:
Male Sinch Plug
5 4 3 2 1
9 8 7 6
Viewed looking into the plug going into
the monitor socket.
Pin connections are as follows:
Male Sinch plug Din plug
1 ]]]]]]]]ground]]]]] 5
join ] 2 ]]]]]]]]Red]]]]]]]] 1
together] 3
4 ]]]]]]]]Green]]]]]] 2
5 ]]]]]]]]Blue]]]]]]] 3
8 ]]]]]]]]Sync]]]]]]] 4
Join pins 2 and 3 with insulated wire.