The BRC as a baseband monitor.

[Geordie McBoyne]

BRC 2000 as a baseband monitor.  It is well known the BBC modified the 2000 CTV as a monitor.  Reference to the IF panel circuit diagram we see that the chroma signal is picked off from the 405 video demodulator diode W2 and the 625 luma from demodulator diode W1.  The 6Mhz intercarrier sound comes from W2. The circuit description informs us that both demodulator diodes remain in the secondary circuit of the IF transformer to maintain a constant load in order that the response curve is unaltered. It should be possible to introduce a CVBS input to the BRC2000 and still allow "off air" reception as well.   An additional amplifier will be required to raise the 1 volt input video luma signal to the level required by the video board.  The same amplifier can extract the 4.433Mhz chroma signal which can be buffered by an emitter follower and routed to the chroma board.  So it follows the inputs of the luma and chroma boards can receive switched input signals either from either the baseband input or the IF panel and tuner.  The audio signals will also require "off air" or baseband switching.  
A viable project?
The BRC has the advantage over other dual standard colour TVs in having a fully isolated chassis.

Geordie McBoyne.
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[ppppenguin]

I've seen one of these with the back off. I think the BBC used it as an RGB input monitor only, without the decoder. They also added pincushion correction. Official BBC mods pincushion attached, taken from scan of very poor photocopy.

When I had an ex rental 2000 as our main TV back in the 1970s I fitted the transductor etc (all from Manor Supplies) and it worked just fine. Though the transductor makes a horrible magnetostriction noise.

[Geordie McBoyne]

Hi Jeffrey, the BRC 2000 certainly lends itself for RGB only. The set I'm considering for conversion to baseband inputs is the "Queen's Speech" Marconi 4701 that appeared December 2015 on the other two vintage radio and TV forums.

Geordie McBoyne.

[ppppenguin]

The set I saw was at BBC research department where I spent a happy year between school and university. 1974/5. Never saw it working but have this dim memory of missing panels. Presumably IF and decoder.

It wasn't just these monitors that lacked decoders. Others of the period such as Prowest PM22/7 had the decoder as an option.

[Kan_turk]

BBC (and other) practice at the time was to feed colour monitors with RGB - often from an outboard BBC designed PAL (and earlier NTSC) decoder - this practice allowed monitors to be independent of colour system which was important especially before the decision on what system was going to be employed had been made