More circuit help required please

Tony Duell ard.p850ug1 at
Sun Jan 8 11:21:39 CST 2017

> I photographed both sides of the board and merged the pictures together to
> make a front/back composite. The trace for the cathodes of the 3 diodes
> links together on the back of the board and doesn't go anywhere else. The
> front trace from V302 cathode goes straight to R312. The anodes DO link with
> the monitor driver board through the connection marked MON though.

OK, probably some kind of luminance signal. Was there ever a monochrome
version of this unit?

> One of the reasons I'm asking these questions is I'm trying to see if
> there's another source of composite sync given that the MR9735 itself
> doesn't do it, even though it should.

I doubt it.... Why would there be?

Is the MR9735 doing anything? Is it accessing memory, for example?
I still wonder if it has to be initialised (say to vewdata rather than teletext
mode) and if this is not occuring.


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