torch@attctc.Dallas.TX.US (Jay Finger) (02/01/90)
I know this same type of question has probably been answered eleventy zillion
times, but I didn't pay attention to them then...
I've got a 512KE (which started life as a 128 back in Dec 84!). Every now
and then the right edge of the screen will flicker/vibrate/shake (I'm not
sure how to describe this) rapidly. Sometimes it's the entire screen
at once, other times it does it so fast that each scan line gets a
different amount of distortion so it looks like there's some noise in the
video.
This usually happens for about 10 seconds, and then stops. It might start
doing it again a few minutes later, or a few days later. For a very long
time it appeared that it had no correlation to how long the computer had
been turned on (i.e. not a thermal problem). It's been doing this for about
two months, but until recently it wasn't bad enough to make me get off
my a.. and look for help/advice. But for the past couple of days it has
been fairly consistent in doing it for a couple of minutes when the computer
is first turned on, and then after it's been on for a while the problem
shows up more often.
Can somebody please tell me what needs to be done to get this fixed? What
do I need to do to fix it myself, and if I do it myself what kind of
problems will I have later on if I actually need to get the video/analog/p.s.
board replaced?. I'm quite handy with a screwdriver and soldering iron, and
know the difference between a resistor and cap, etc, etc, etc. But I've
never done any work around CRTs before, so I'll need a good description of
what needs to be discharged, and the best ways to go about discharging
(i.e. a resistor to bleed the charge off, or the blade of a screwdriver :-).
Also, advice on where to get the parts (if someplace other than the corner
Radio Shack).
Many thanks in advance,
Jay Finger,
{ames,mit-eddie}!attctc!torch
ames!torch@attctcArmadillo@cup.portal.com (Russ Armadillo Coffman) (02/02/90)
Jay - Had the same problem many times - between my original 128 and my current Plus, I've owned six power boards. The last blown board was prolly my fault (long story), but it was dying anyway. Q&D way to forestall the inevitable: I'll ASSume you can open the case (and you remember to disconnect power cord etc.). Look at the big wires coming off the end of the CRT that go to the power board. They go to a large connector. Remove the cardboard from the power board. Resolder the pins of this large connector (four, I think). Get 'em nice and hot. I saw one board that had almost NO solder here, so you may have to add some. While you're in there, unplug both ends of this connector and reseat it firmly - plug and unplug it a few times, in fact. Just these two steps alone solved the problem you described for me just this week. Well, here's the long story. I put the cover back on without replacing the cardboard - "just for a sec," to test. A couple of protruding blobs made contact with the inside of the case's RF coating when I whacked the case to see if I could make it act up again - POW! Left a couple of black marks on the inside of the case. Until then, all the shaking was gone. <sigh> Being unemployed, I dug up the name of a local (Sillycone Valley) component-level repair shop. Stopped by, and ten minutes and $75 later left with a spiffy new power board. * I challenge Apple Computer Inc. or any dealer to top that example of cost and service!! * But I digress. Anyway, first discharge yer CRT by hooking a wire with an alligator clip at each end to a screwdriver and one of the lugs at the top left corner of the CRT (as viewed from the rear). Insert the screwdriver tip under the suction cup and make contact. Use a wet neighbor or small animal to test for stray high voltage before proceeding (jes' kiddin'). The above may keep you going from anywhere from a few days, or, as in one time on my Plus, a whole year. When Apple engineering finally catches up with you, try to find a local equivalent to my guy. Oh - for locals, he's Robert Stokes, Design Services, 408-246-8809 or 408-982-0950, in SJ off 101 & San Tomas Distressway. Sure beats $200+ at a sanforized Apple dealer. Good luck, -Russ Mac Guy Sales & Corp. support whiz Still looking for MacWork
ajauch@ics.uci.edu (Alexander Edwin Jauch) (02/03/90)
In article <11248@attctc.Dallas.TX.US> torch@attctc.Dallas.TX.US (Jay Finger) writes: >I know this same type of question has probably been answered eleventy zillion >times, but I didn't pay attention to them then... Ready, 11 zillion and one. > >I've got a 512KE (which started life as a 128 back in Dec 84!). Every now Great! My Plus started out as a "Fat Mac" (512K w/ 400k drives)! >and then the right edge of the screen will flicker/vibrate/shake (I'm not >sure how to describe this) rapidly. Sometimes it's the entire screen >at once, other times it does it so fast that each scan line gets a >different amount of distortion so it looks like there's some noise in the >video. You have a bad power supply. More accurately, you probably have a bad flyback transformer. There are several other parts in the power system that could cause this but this seems to be the most common. Try the solder trick mentioned earlier, if this does not work phone around for a *non apple* mac repair house. Apple's standard parts are sub-par as far as I'm concerned. This problem is fairly common and they should be able to help you out. Alex Jauch ajauch@bonnie.ics.uci.edu Dis: I aint no hero, just a dude.