[comp.sys.3b1] screen is beginning to jump around

wouk@alumni.colorado.edu (Arthur Wouk) (04/25/91)

the screen on my 3b1 is beginning to get a bit jumpy: not distorting,
but moving around a bit, then stabilizing. right now it is stable.
could this be from exterior power, or am i beginning to experience
power supply failure?

anyone with a spare 3b1 power supply to sell?
-- 
arthur wouk 
internet: wouk@cs.colorado.edu

dt@yenta.alb.nm.us (David B. Thomas) (04/26/91)

wouk@alumni.colorado.edu (Arthur Wouk) writes:

>the screen on my 3b1 is beginning to get a bit jumpy: not distorting,
>but moving around a bit, then stabilizing. right now it is stable.
>could this be from exterior power, or am i beginning to experience
>power supply failure?

I have seen this problem on more than one machine.  In all cases, cleaning
the contacts on the main multipin connector that plugs into the monitor's
circuit board (cable coming from the motherboard) fixed the problem.  Sometimes
I have had to repeat the cleaning.

					little david
-- 
Unix is not your mother.

jfischer@cbnewsm.att.com (james.fischer) (04/26/91)

		Yep, sounds like the power supply is getting
		flaky, but it COULD also be the high-voltage
		components in the CRT-case portion of the
		cabinet - I would suggest finding a scope
		and looking at the AC in, the outputs of the
		power supply, and the ins and outs of the
		high voltage board in the CRT enclosure.

		If it IS the power supply, AT&T will sell
		you a new one, if you send in your bad one
		in exchange.  the comcode is 405076597, and
		the phone number is 800-222-7278.

					james fischer
					UNIX System Laboratories
					...att!gcss20!gcjhf
					...attmail!jfischer	

dnichols@ceilidh.beartrack.com (DoN Nichols) (04/28/91)

In article <1991Apr26.165755.20542@cbnewsm.att.com> jfischer@cbnewsm.att.com (james.fischer) writes:
>
>		Yep, sounds like the power supply is getting
>		flaky, but it COULD also be the high-voltage
>		components in the CRT-case portion of the
>		cabinet - I would suggest finding a scope
>		and looking at the AC in, the outputs of the
>		power supply, and the ins and outs of the
>		high voltage board in the CRT enclosure.
	[ ... ]

	Isn't this the symptom one gets when the capacitor on the crt board
is starting to fail?  I've not experienced it, but I seem to remember the
description in previous articles.  The capacitor in question is spelled out
in the FAQ file, if I remember properly. -- No, I just checked, and it isn't
there.  It must be somewhere in the previous months which are archived on
tape, somehwere.  (Not exactly quick reference while trying to answer a
questions.  Does anyone have the capacitor location/designator more readily
available?

	Good luck
		DoN.
-- 
Donald Nichols (DoN.)		| Voice (Days):	(703) 664-1585
D&D Data			| Voice (Eves):	(703) 938-4564
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