Date   : Sat, 06 Nov 2010 00:24:17 +0000
From   : jgh@... (J.G.Harston)
Subject: BBC colour video out

> Also, the monitor connection at the back is outputting in black and   
> white only. How might I fix that?

Matthew Rose wrote:
> The monitor connection? are we talking the composite video? From   
> memory this was always in B&W.
> http://mdfs.net/Info/Comp/BBC/Monitor/BBCtoTV.htm

Ah yes, paragraph 6. Being a software person I tend to glaze over
somewhat when it gets to fiddly bits of hardware. Plus, the only
composite video monitors I ever had were monochrome ones.

----8<----
As standard, all BBCs output monochrome composite video signals (luminance),
but it is possible to modify the motherboard to supply the missing chrominance
signal. The modification is quite easy to perform.

6.1. BBC Micro issue 1, 2 and 3 motherboards
   A 470 picofarad capacitor must be fitted between the emitter (marked 'e') of
   Q9 and the base of Q7 (the central leg).
6.2. BBC Micro issue 4 and 7 motherboards
   Link 39 must be made. This can be found next to the modulator in the far
   right hand corner of the PCB.
6.3. BBC Micro model B+
   Link S26 should be made.
6.4. Master 128 issue 1 motherboards
   A 470 picofarad capacitor should be connected between the east leg of R137
   and the east leg of R153. These are located to the east of the modulator.
----8<----

-- 
J.G.Harston - jgh@...