Re: Mk14 vdu
Thanks for the info - I believe it is a fact that the composite output circuit ideally needs to be distinctly different depending on whether you are driving a UM1233 modulator (as per original) or composite video directly, for one thing a composite video input on a TV or display typically has a rather low termination resistance of 75R.
If you followed any of John Erland's adventures in his ZX81 thread you may have noticed that his replacement 'ULA IC' even had selectable output modes, depending on whether it was going to output to a modulator or output direct composite video.
Both of those conditioning circuits look as though they could be built inside the empty shell of a UM1233 modulator, with the 'UHF out' connector then becoming composite-out.
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