[sci.electronics] Hacking Screen Blanking on a vt220

bph@buengc.BU.EDU (Blair P. Houghton) (08/07/89)

Thanks to many fortuitous monetary circumstances, and the joys of
living three blocks from Eli Heffron and Sons, Inc., I am now the proud
owner of my very own pre-owned DEC vt220 terminal (alla you guys at DEC
congratulate me, now) and it's a babe.

What I'd like to do with it, though, is to reduce the amount of time
before screen-saver-blanking occurs.  It's set to 30 minutes, and
(it appears) there is no way to change that from outside.  Basically,
I can't get there from here.

What I imagine I can do, however, and I'm not above soldering things
and hanging buttons on wires out the ventilation louvres, is locate
the blank-it-signal line and kludge it so I can force it low myself,
or move a connection on a counter to shorten the reset-time.

Ahh, I ask, but _where_ to look for these signals?  Anyone know?

Some other questions that come to mind are:

	Does DEC cover used boxes?
	If so, will this not void my warranty?
	Can I get a schematic for a discontinued item from DEC?

				--Blair
				  "Would it be easier to
				   just bash the CRT with a
				   hammer and replace it when
				   I get back from the bathroom?"

bph@buengc.BU.EDU (Blair P. Houghton) (08/08/89)

In article <1989Aug7.044043.2369@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes:
>In article <3642@buengc.BU.EDU> bph@buengc.bu.edu (Blair P. Houghton) writes:
>>...What I'd like to do with it, though, is to reduce the amount of time
>>before screen-saver-blanking occurs...
>>Ahh, I ask, but _where_ to look for these signals?  Anyone know?
>
>Almost certainly this is a software function and there is no specific
>wire carrying a signal for it.  I think you're out of luck.

Okay, so maybe I have to solder a lot of wires in order to blurt
a control word into the video controller.

Like I said, I'm perfectly used to doing horrendous kludges to
get around misconceptions.

				--Blair
				  "You ever mistakenly believe
				   that you could get parallel
				   control out of a D/A card, then
				   discover that you couldn't, and
				   had to decode one of its analog
				   signals in a sequential controller
				   to do simple stuff like reset a
				   counter somewhere?  You wanna
				   see me do it?  Come on over
				   to the lab.  It's on the bench
				   even as I type...you can hold the
				   breadboard while I solder the other
				   half-million wires onto the other
				   six-dozen op amps and comparators..."