BBC To IBM/PC Monitor          
          BBC To IBM/PC Monitor          
                                         
       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. 
                                         
                                         
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