Ethan Dicks ethan.dicks at gmail.com
Sun Mar 20 23:49:23 CST 2005

On Fri, 18 Mar 2005 11:12:49 -0500, Carlos Murillo
<cmurillo at manizales.autonoma.edu.co> wrote:
> Hi people;
> I found a couple of damaged/parts-scavenged qbus boards which
> I was able to identify as vt278 (decmate) cpu boards...
> Can one connect a terminal to the printer port with
> some special cable, supply power to the board and
> have the thing come back alive and talk to the terminal?
> (the diagrams are at http://www.bitsavers.org/pdf/dec/pdp8/cmos8/,
> file MP00900_VT278_may81.pdf)


>From looking at the prints, I can see where the video chip pumps out H
sync, V sync, and video to the edge fingers... the board also needs
+5, +12 and -12 (for the DRAMs, among other uses).  It's been years
since I tore apart a VT100 (was turning two dead ones into one live
one), but there's nothing magical about them... the video board
schematic is in the VT278 drawings.  If you didn't want to muck around
inside a real VT100, you'd need a mono video monitor that can handle
the sync rates for 80 col and 132 col, whatever they happen to be
(never poked at the video signals with an o-scope, so can't even
hazard a guess).

If you decide that it would be too much trouble to get that 'naked'
VT278 board working, feel free to let me know... I wouldn't mind a
spare for my DECmate I.


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