PET composite video adapter

Ethan Dicks ethan.dicks at usap.gov
Mon Oct 13 14:26:08 CDT 2008


On Mon, Oct 13, 2008 at 08:21:11PM +0100, Phill Harvey-Smith wrote:
> Ethan Dicks wrote:
> >P.S. - I found another type of composite circuit using a CD4011 as an
> >inverter and a CD4066 to mix the signals, 
> 
> Sounds like the circuit I have here from "The PET Revealed".

That is very likely, though I probably found a copy of just the
diagram somewhere on the web.  I have a copy of the book at home,
but I didn't bring it with me.
 
> >					but for some reason I don't
> >have all the components labelled on my drawing - the cap on hsync in
> >particular.  
> 
> It's not labeled on the diagram in the book, nor does the text say what 
> value it is.

That would explain why my schematic doesn't have it, then.
 
> >		One interesting variation with that one is that the 'LS02
> >circuit has a 1.5K pulldown on hsync between the cap and the gate,
> >while the CD4011/CD4066 circuit has a 10K pot.  How much adjustment on
> >hsync is likely to be needed between the PET and the first gate of the
> >composite circuit?
> 
> The text in the book says "You may encounter problems with the 
> horizontal hold, but these can usually be cured by adjusting R1", and 
> goes on to speak of low quality monitors or converted TVs...

Ah.  Thanks much for that.  I have plenty of small PCB pots... easy to
fit on in.

-ethan
 
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Ethan.Dicks at usap.gov            http://penguincentral.com/penguincentral.html



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