> Reply-to: <[EMAIL PROTECTED]> (Vintage Macs) > To: <[EMAIL PROTECTED]> (Vintage Macs) > Date: Mon, 18 Mar 2002 20:11:51 -0500 > From: the pickle <[EMAIL PROTECTED]> > Subject: Re: Apple 15" Multiscan Repair
> At 19:40 -0500 on 18/03/02, [EMAIL PROTECTED] wrote: > > >I have had these apart and find nothing "obvious" but... > > Check the CRT-end PCB for cold solder joints. That's usually it. > > the pickle Hardest part is getting tin pan off the CRT board if top isn't snappable off. Go slow, suck out excess solder that holds down tin pan at edges first and double check they're free, if tabs is twisted or bent over, straighten them. When that pan edges are all freed, melt the center tab if it has one that touching middle of the circuit board while carefully lifting pan away while solder is molten. The CRT board (the board that plugs into tube's end), and anything else on the mainboard. On these, solder joints commonly cracks caused from thermal expansion cycles. 1. Easy to spot: cracked rings. Solder them. 2. Dull not too apprently clear it's bad, resolder anyway. 3. Very Sneaky ones. Looks good but component leads isn't bonded to solder. I see this commonly on shiny red dipped capacitors and normal capacitors sometimes. Usually easier to find bad joints shows up if you flex the free-standing component part and connectors. Cracking are often found on big component leads, any big pins, connectors pins, hot parts even it has heatsinks or not. Hot parts usually shows up as darkened spots just like toasting bread on circuit board itself. Heat it to get old solder melted and add solder to it with bit of solder wire, while there, keep iron there for one to two seconds more then remove both iron and poised solder wire, you want solder very liquid not hot solder of dull, sticky, mushy. Use fine tip, 30W~40W please. You want beauiful shiny solder, very minor crazing is ok. If too much solder "looks like round pumpkin", wipe hot iron tip clean, melt it again , maybe use solder sucker without adding more solder, remove the iron, repeat after cleaned iron if needed, if removed too much add bit of fresh solder to get correct kind. This usually works too on removing solder bridges if accidently made. Dry solder joints I find that meaning misleading. Cracked rings is caused by too little solder and broke apart when stressed by flexing, viberation, heat cyclings. You can have a decent solder joints but they went "bad" from aging especially if component leads were not clean enough, may looks like it's not "wetted". Have a care not to let your hands rest on the circuit. Very sharp pins and sometimes that capacitor somewhere is still charged - Buzzt! - Ahhhh! Always make sure you can see unplugged power plug for that monitor and don't plug while it's all apart or cover off, double check everything are in place, all plugs in right places before cover goes back on. Safety: If you must adjust focus or something else, use plastic tools for that and do it with one hand BEHIND YOUR BACK. That's the rule and this breaks accidental dangerous living circuit this way. Injuries, possible death and shocks happens when electric get across either arm to arm or arm to leg or any thing between two points. If your feet and that floor is wet or damp even that feet is bare or shod of any kind, don't do it. Move to dry location. In that middle of living circuit is your heart may stop. If one part got shocked while your hand is behind that back and feet are dry and not making to another connection on that living circuit or ground, all you get is a OW!!, maybe hit something else when jerked away and got cut. If you must wiggle, tap, push around or jiggle parts with monitor live to ferret out hard to locate faults, use long wooden or plastic chopsticks or strong dowel wood or plastic. Not pens, not pencils, they're too short and often has metal or conductive stuff (lead) in it. Basically don't touch live monitor's guts except metal frames that holds main board and screws that holds tube to bezel, plastics. And stay away from that suction cup on that tube's bell. I have seen bluc arc out to grounded tool from under it even just lightly touching at the edge of that suction cup with a loud snap! Cheers, Wizard -- Vintage Macs is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Enter To Win A | -- Canon PowerShot Digital Cameras start at $299 | Free iBook! | Support Low End Mac <http://lowendmac.com/lists/support.html> Vintage Macs list info: <http://lowendmac.com/lists/vintagemacs.shtml> The FAQ: <http://macfaq.org/> Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive: <http://www.mail-archive.com/vintage.macs%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
