New subject: VAX collectors attention

30 Nov 1998

Foxnhare (who are you anyway?  I've seen the address before.  You're not
Larry Anderson by any chance are you? :-) ) wrote:

...
   From: Doug
Spence &lt;ds_spenc(a)alcor.concordia.ca&gt;
 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 just noticed
for the first time (!) that the "PARALLEL USER PORT" has
 pins labeled "T.V. Video", "T.V. Vertical", and "T.V.
Horizontal"!  Has
 anyone actually connectd a TV or external monitor to a PET? 
 There are plans for a composite video converter using those pins in Nick
 Hampshire's PET Revealed, I think it only works on the older 9" screen
pets
...
  and not the 12" ones.  The reason for it being on
the user port was for deaier
...
  diagnostic testing. 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.

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.

Philip.

PET Video (was: Replacing 6550s) & 128