Experiences with a composite video mod for a Sinclair ZX81

Adrian Graham witchy at binarydinosaurs.co.uk
Sun Jan 3 06:34:20 CST 2016

On 03/01/2016 02:06, "Terry Stewart" <terry.stewart296a at gmail.com> wrote:

> It's interesting that none of my present TVs would tune properly to the RF
> of the ZX81 but they will with some of the other RF only computers like the
> Coco 1 and Atari 400?  More circuitry in the latter perhaps...

Going from an old, old memory from when TVs became auto-tune rather than
dial-in or 'press-a-button-and-hold-until-something-happens' I recall it was
to do with the 'black level' from the ZX81 in that it was too great and
caused the autotune mechanism to skip it altogether as it wasn't seen as a
useable signal.

Hopefully someone else can elaborate on that.

Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer

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