PET Composite Video

From: Larry Anderson <foxnhare_at_goldrush.com>
Date: Tue Dec 1 20:32:08 1998

> From: Philip.Belben_at_pgen.com
> Subject: Re: PET Video (was: Replacing 6550s) & 128
>
> Foxnhare (who are you anyway? I've seen the address before. You're not
> Larry Anderson by any chance are you? :-) ) wrote:

Yep, the login was my wife's idea... Fox: an old definition for my middle
name, Todd, and Hare: for her last name.

> >> From: Doug Spence <ds_spenc_at_alcor.concordia.ca>
> >> Subject: Re: Replacing 6550s
> >
> >> (I especially find it cool that they list various part numbers for the
> >> connector. :) )
> >
> > Digikey is the best source for inexpensive PET compatible connectors.
> > (1-800-DIGI-KEY) along with a ton of other cool parts.
> Many thanks for that. I know where to turn next time I'm looking...

I think the last batch of 12/24 PCB connectors from them cost me about $18
(for 10). Very reasonable!

[snip!]
> I thought the video signals were there on later machines too, but I can
> well believe it might not work on the 12 inch screen models.

I would think you could get a multi-sync to do it, but the way the screen
behaves I think the fat-forty and 80000 series were able to change sync rates.
 (Of course what do I know I'm just mainly a software guy).

> My experience is that Nick Hampshire's circuit doesn't work at all. Using
> the same two chips, 4011 and 4066, the correct procedure (sorry. The
> procedure that worked when I tried it) is to combine the two syncs with the
> 4011, invert (I think - not sure about this one) with another 4011 gate,
> and use that to gate the video using the 4066. Works a treat. They tried
> it at school, too (don't know what circuit tho'), and got a grey background
> for the white text. I imagine a series capacitor might help, but I've not
> tried it.

Could ya like draw it out or something... I would really like to have a
composite output on the PET (ohh could do WWW quick-time animated movies of
such classics as Drameda! or Dance! - PET character animated shorts) 100k of
video for a 5K program animation :) Actually would be better to screen
capture it off of an emulator and then you can compress it way down to say 60
k or less..

> From: ard_at_p850ug1.demon.co.uk (Tony Duell)
> Subject: Re: PET Video (was: Replacing 6550s) & 128
>
> [Composite video adapter]
>
> > My experience is that Nick Hampshire's circuit doesn't work at all. Using
> > the same two chips, 4011 and 4066, the correct procedure (sorry. The
>
> I've never tried that one. I've used modifications of the TRS-80 Model 1
> circuit and the BBC micro circuit with no problems at all. The latter is
> simpler, so I'll describe that. But the output has a little DC offset
> that some (a _very_ few) monitors object to.
>
> Start by Xoring HSync and VSync to get a CSync signal. I normally use a
> 74LS86 for this. But the XOR-from-4-NANDs using a 74LS00 once got me out
> of a hole when I couldn't find any '86s. Invert CSync to give Csync/
> using either another section of the '86 or a suitable TTL inverter.
> Alternatively make an XNOR gate from 4 NORs.
>
> You now combine video and CSync/ using this circuit

Or the complete circuit of this? I would really like to get a composite
circuit for the PET FAQ on-line One could concevably make a portable PET
(yeah, the PET is kinda portable, but not as much as an SX 64 or 128D) if such
a circuit was available. ;>
Received on Tue Dec 01 1998 - 20:32:08 GMT