[comp.sys.mac.hardware] screen flickers on a plus

CHEE77@elroy.uh.edu (Fred Schulz) (11/16/89)

What would cause the screen to flicker on and off. After my plus has
been on for a while, tapping the sid will cause the screen to go off, or
on. I sure don't want to take it to a dealer to have the analog board
replaced. I've heard mention of a cracked solder joint, but saw no
obvious suspects when I opened it up.

Any suggestions? Thanks.

gordon@cs.washington.edu (Gordon Davisson) (11/17/89)

In article <4963@elroy.uh.edu> CHEE77@elroy.uh.edu (Fred Schulz) writes:
>What would cause the screen to flicker on and off. After my plus has
>been on for a while, tapping the sid will cause the screen to go off, or
>on. I sure don't want to take it to a dealer to have the analog board
>replaced. I've heard mention of a cracked solder joint, but saw no
>obvious suspects when I opened it up.
>
>Any suggestions? Thanks.

The solder joint you're looking for is on the connector for the cable to
the motherboard.  It's a 10-pin connector near the middle of the analog
board.  It has 9 pins in a group, then a gap, then one by itself (toward
the front of the machine).  The isolated pin is almost certainly your
problem.  The cracks I see here are usually very thin and can be hard
to see, especially if the solder is shiny.

--
Gordon Davisson
Westwind Computing	(206) 632-8141
4518 University Way NE, Suite 313, Seattle WA 98105

steveg@umd5.umd.edu (Steve Bruce Green) (11/18/89)

In article <4963@elroy.uh.edu> CHEE77@elroy.uh.edu (Fred Schulz) writes:
>What would cause the screen to flicker on and off. After my plus has
>been on for a while, tapping the sid will cause the screen to go off, or
>on. I sure don't want to take it to a dealer to have the analog board
>replaced. I've heard mention of a cracked solder joint, but saw no
>obvious suspects when I opened it up.
>
This is caused from the degradation of some of the solder joints on the power
board.  The usual place too look is along the connectors.  If you can, open the
mac and look at the solder joints along the large connector and along the 4 pin
connector at the top.  (This one is probably under the tape)  You should try to
remove the old solder with a solder sucker if you can.  Simply re-do the solder
joints that are bad and make sure that the solder flows... dont "paint" the
solder on.  In your case, the bad joint is probably on the large connector at
the white wire location. 
When you are done...and things work ok... get a fan!!!

dudek@ai.toronto.edu (Gregory Dudek) (11/20/89)

In article <9849@june.cs.washington.edu> gordon@june.cs.washington.edu.cs.washington.edu (Gordon Davisson) writes:
>In article <4963@elroy.uh.edu> CHEE77@elroy.uh.edu (Fred Schulz) writes:
>>What would cause the screen to flicker on and off. After my plus has
>>been on for a while, tapping the sid will cause the screen to go off, or
>>on. I sure don't want to take it to a dealer to have the analog board
>>replaced. I've heard mention of a cracked solder joint, but saw no
>>obvious suspects when I opened it up.
>>
>>Any suggestions? Thanks.
>
>The solder joint you're looking for is on the connector for the cable to
>the motherboard.  It's a 10-pin connector near the middle of the analog
>board.  It has 9 pins in a group, then a gap, then one by itself (toward
>the front of the machine).  The isolated pin is almost certainly your
>problem.  The cracks I see here are usually very thin and can be hard
>to see, especially if the solder is shiny.
>
  Another common place for a bad solder joint (I had one) is (apparently)
right under the small coil near the C1 capacitor.  On my board, the
paper board covering under the coil was badly browned from the heat 
from the coil and the weaked solder joint was clearly visible.
  This coil in near the rear of the board (as opposed to the connector above).
   
   Greg Dudek