[net.micro.mac] Jerky screen problem

osmigo1@ut-ngp.UUCP (Ron Morgan) (03/19/86)

*I've been having a problem with my mac, and wondered if any of you could offer some opinions.

The past three days, my screen has been "twitching." The movement is chara-
cterized by shifting in one direction and then back, "waves" passing through
the text, as if I were looking through a clear gel which wobbled from time
to time. When it's at its worst, I see jagged edges running up and down the
sides of the display, often connected across the screen by lines. 

All of these events are fairly quick. They last from about .2 to .4 seconds.
Factors:

About a month ago, I got a third-party upgrade which involved a board swap.
The cost was $150.00.

The last few days, a roofing crew has been working on the roof of my apartment
building. 

This mac has been on an average of probably 12-16 hours a day for 2 years.
It is kept covered when not in use. Could I be getting power supply problems?

Thanks in advance,
Ron Morgan
osmigo1@ut-ngp.UUCP
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spector@acf4.UUCP (David HM Spector) (03/20/86)

Sounds like your power supply the ("Analog Board") is getting a little flakey.
Mine did that for a little while before it fried my Macintosh.  ...Thank 
G-d for AppleCare.


					Dave Spector
					NYU/acf Systems Group

werner@ut-ngp.UUCP (Werner Uhrig) (03/21/86)

Anyone with this symptom should check and adjust the 5 and 9 Volt voltage
level coming off the analog board.  As a matter of fact, everyone should
do that, just for peace of mind.  This is especially important after an
upgrade to 512K or to Megabytes.

My Mickey "acted up" after I upgraded to 2Meg and when I checked, my
5 Volt level at the plug where the ribbon-cable coming from the main board
connects into the analog board, showed only 4.3 Volts.

From what I have seen, *EVERYONE* should check (have someone check) and
adjust all settings on the analog board right after purchase and anytime
the machine is open and had not been checked for a while.  Of course,
if you are still in warranty or if you are not absolutely sure what you are
doing, I encourage you to pay the few bucks this might cost you to have a
certified Apple tech do this for you.  On the other hand, I myself don't
really have much trust and confidence in the "run of the mill" (lawyer,
doctor, car-mechanic) technicians, but at least you can sue them (maybe),
whereas you can't even kick yourself in the rear effectively....  ((-:

below I enclose a list of the pin-assignments of the ribbon-cable connecting
the analog board with the digital (main) board
	(copied from Beck-Tech's poster-schematics)

	PIN	ASSIGNMENT

	1	VIDEO
	3	H SYNC
	4	SOUND
	5	V SYNC
	6	+5V DC
	7	GND
	8	-12V DC
	9	GND
	10	+12V DC
	11	BATTERY


		I hope this helps,		---Werner

Disclaimers:   YES - ALL