Experiences with a composite video mod for a Sinclair ZX81

[Eric Christopherson]

On Sun, Jan 03, 2016, Adrian Graham wrote:
> 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'

What's this about holding a button?

> 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.

-- 
        Eric Christopherson