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2.8) Can I connect a SCART monitor to my Acorn machine?




Description

This article is from the comp.sys.acorn FAQ, by Paul Vigay with numerous contributions by others.

2.8) Can I connect a SCART monitor to my Acorn machine?

If you have an older Acorn machine with a nine pin video socket, then yes and here is the wiring diagram :-

    .------------------------.    Arc 9-pin plug
    \    1   2   3   4   5   /
     \                      /
      \    6   7   8   9   / Case
       '------------------'
        _____________________
       |19                  1|    SCART 21-pin plug
       | | | | | | | | | | | |
      /                      |
     / |  | | | | | | | | |  |
    /___20_________________2_| 21 (metal casing)

A SCART connector is also known as a Euroconnector or a Peri-Television connector.

                Arc             SCART
Case            | ------------- 21              Case
Red             1 ------------- 15              Red
Green           2 ------------- 11              Green
Blue            3 ------------- 7               Blue
CSYNC           4 ------------- 20              Composite video input
Ground (0V)     6 -+---------+- 13              Red ground
Ground (0V)     7 -+         +- 9               Green ground
Ground (0V)     8 -+         +- 5               Blue ground
Ground (0V)     9 -+         +- 13              CVBS video ground

Ideally each ground wire should be linked to a separate Arc pin. Also, depending on your SCART monitor, pin 16 may need a +5V input to it. Unfortunately the Arc 9 pin socket does not provide a +5V output so this will have to be sourced from somewhere else.

If you have a newer Acorn machine, with the 15 pin high density video socket then you need this kind of wiring :-

       .--------------------.   15-pin VGA style plug
       \    1  2  3  4  5   /
        \ 6  7  8  9  10   /
         \ 11 12 13 14 15 /
          '--------------'

Connections:

Arc                               SCART
 
1 red ---------------------------- 15
2 green--------------------------- 11
3 blue---------------------------- 7
4 ID[2] nc
5 0V (test)
6 red rtn------------------------- 13
7 green rtn----------------------- 9
8 blue rtn------------------------ 5
                  75 ohms
9 +5V-------------/\/\/\/--------- 16
10 0V----------------------------- 17,18
12 ID[1]-------------------------- 8
11 ID[0] <--13 |
13 HSync -->11 |
                    120 ohms
14 CSync------------/\/\/\/------- 20
15 ID[3] nc

Notice the two resistors. Also notice that the HSync output (pin 13) of the 15-way plug has to be connected to the ID[0] input (pin 11) of the same plug. (Be aware I have no direct confirmation that this wiring works.)

As is usual care must be taken when doing this procedure. Older Acorn machine did not have their VIDC chips fully buffered and unplugging/plugging cables from the video socket while the machine is turned on can cause damage to the video circuitry.

If you want to connect a BBC B computer to a Scart monitor, there are some online wiring diagrams at www.astro.livjm.ac.uk/~bbc/monitor/monitor.html

 

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