stuart@ihlpe.ATT.COM (S. D. Ericson) (11/23/88)
My Mac II monitor started acting very strangely lately. After being turned on a few minutes, the monitor will "snap" periodically, about every minute or so. The "snapping" causes the screen to jump and sometimes even go completely blank, necessitating a reboot of the machine to get the display back. Being curious, I took the case off the monitor, disconnected it from the Mac and plugged it in stand-alone. The snapping persisted. It seems to slowly build up a large amount of voltage and then discharge it. The sparking can be seen very plainly in the tube, but I'm not sure it that is where the sparking is taking place, or if that's jjust an electrical reaction of the tube to an outside voltage arc. This seems to be a problem in the high-voltage circuitry, so it's not so much a Mac problem as a TV tube type problem. (It arcs when NOT connected to the mac.) Anyone have any ideas as to what may be causing this? Any TV technicians on the net? I'd hate to have to go to Apple's "board-swap-fix" prices for a loose connector or something... Thanks in advance... Stu -- Stuart Ericson AT&T Bell Laboratories USEnet: att!ihlpe!stuart IH 2H210 ARPA: stuart@ihlpe.att.com 2000 N. Naperville Road Voice: (312) 979-4491 Naperville, Il 60566-7033
cook@stout.ucar.edu (Forrest Cook) (11/29/88)
In article <3825@ihlpe.ATT.COM> stuart@ihlpe.ATT.COM (S. D. Ericson) writes: >My Mac II monitor started acting very strangely lately. ... >Stu A good method for dealing with your high voltage arcing problem is to cover the leaky area with TV corona dope, availible from most tv repair parts suppliers, the Ratty old Shack might carry the stuff. Do the following: - Unplug the monitor. - Take a long flat screw driver and connect it to the chassis ground with a clip lead. Put the tip of the screwdriver under the suction cup on the side of the tube and discharge the tube. Wait a few seconds for the charge to build up and discharge the tube again. Be careful, >10Kv bites. - Pull the suction cup connector off of the crt, put the grounded clip on the exposed crt 2nd anode just in case. - clean the dust off of the area that is sparking, presumably somewhere on the flyback transformer or rectifier. - apply the corona dope around the leaky area and let it dry off. - put everything back together and hope for the best. - If there are any high voltage connections on the flyback that have sharp points, round them off with a file or solder. ^ Forrest Cook (The preceding comments were my Opinions) ^ /|\ /|\ /|\ {husc6 | rutgers | ames | gatech}!ncar!stout!cook /|\ /|\ {uunet | ucbvax | allegra | cbosgd}!nbires!ncar!stout!cook /|\