Broken Macintosh Classic

iHackintosh

macrumors newbie
Original poster
Jan 11, 2012
13
0
Ohio
I have a December 1991 Macintosh Classic running System 7.0.1. It's always had some difficulty booting but recently it hasn't worked at all, the screen flickers and shows a Sad Mac. (Along with a sad mac user soon after.) I know several people who used that model and said that it was defective RAM so I bought a 6MB RAM card but that still didn't work... any ideas?
 

MacTech68

macrumors 68020
Mar 16, 2008
2,224
167
Australia, Perth
Probably surface mount electrolytics have leaked and etched tracks on the logic board. Very common.

Removing them is a tedious job and you'll need to clean the electrolyte from the board, repair any etched tracks and then replace them.

I usually use surface mount Tantalum capacitors (if you can find the right case sizes to suit the solder pads). Other people replace them with radial thru-hole electrolyics by bending the leads at a right angle. Not the best solution but it works.

Removing the originals is not always easy, and care must be taken not to rip the solder pads from the PCB.

Leaving the machine switched on and allowing it to warm up might allow it to work (try resetting the machine after it's been on for 30 minutes). Even if that does work, it's only going to get worse. Those caps will need replacing. :(
 

iHackintosh

macrumors newbie
Original poster
Jan 11, 2012
13
0
Ohio
Wirelessly posted (Mozilla/5.0 (iPhone; CPU iPhone OS 5_0_1 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Version/5.1 Mobile/9A405 Safari/7534.48.3)

Could I replace the logic board entirely with a working one?
 
Last edited:

MacTech68

macrumors 68020
Mar 16, 2008
2,224
167
Australia, Perth
Wirelessly posted (Mozilla/5.0 (iPhone; CPU iPhone OS 5_0_1 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Version/5.1 Mobile/9A405 Safari/7534.48.3)

Could I replace the logic board entirely with a working one?
Yes, but finding one WITHOUT this problem is near impossible, sadly. :(
 

0ranges

macrumors newbie
Jan 8, 2012
24
0
You can remove the logic board, run it in the dish washer for about a half hour with the ram and ram card removed. Make sure the whole board gets sprayed and not just one side. I did this with a classic which had some leaky caps and brought it back to life. Sometimes it works, you never know. Don't be afraid to put the board in water as they were washed with water during the last part of manufacture. One day every old board in every mac will need to be dishwashed. If it does work, it won't last forever (what does?) live for today :D

Oh! I almost forgot, don't yell at me if it makes it worse! Google: dishwash macintosh classic
 

JacaByte

macrumors 6502
Dec 26, 2009
315
0
Dishwasher?!? D:

I would get a tub that's big enough to hold the mainboard, clean it with soap and water and rinse it with distilled water.

Then I would wait for the tub to dry (let it air dry, do not dry it with a towel or something!) and inspect it for spots. Distilled water will not leave spots when it dries, so if you find spots that means there's some residual soap/dust in the tub, which can potentially short electronics, and you'll have to wash the tub again.

Theoretically electronic devices can operate underwater, so long as the water is pure H2O. Ions like iron, sodium and potassium that are commonly present in tap water are what cause shorts. What you are doing here is decreasing the chances that the mainboard will be shorted out after drying.

Now that the tub is dry, put your mainboard in it and cover it with distilled water. Let it sit for a while, you want as much of the electrolyte on the board to dissolve as possible. If you have a means of warming the distilled water without contaminating it then that might help the electrolyte dissolve. (Don't go nuts though, I'd suggest a temp of between 100 and 120 degrees F.)

After the mainboard has sat for awhile remove it from the distilled water/electrolyte solution and let it dry someplace safe. Again, let it airdry; do not use a blowdryer or something to speed the drying process! If you live someplace with tons of humidity you might want to put the mainboard in a static free bag with a desiccant of some type to soak up the distilled water; rice works well. Let it dry for several days, you want the board to be completely dry before you put it back in your Mac!

After the mainboard has dried you might want to identify the electrolytic caps in question and either remove them yourself or have a friend with surface mount soldering experience remove them for you. If you are able, try to identify the etched traces on the mainboard (if any) and repair them. Then replace the caps. (The earlier suggestion of tantalum caps is an excellent one.)

Once that's complete, put the mainboard back in the Mac, reconnect everything, apply power, turn the sucker on and cross your fingers. Good luck!
 
Last edited:

Lil Chillbil

macrumors 65816
Jan 30, 2012
1,322
96
California
You can remove the logic board, run it in the dish washer for about a half hour with the ram and ram card removed. Make sure the whole board gets sprayed and not just one side. I did this with a classic which had some leaky caps and brought it back to life. Sometimes it works, you never know. Don't be afraid to put the board in water as they were washed with water during the last part of manufacture. One day every old board in every mac will need to be dishwashed. If it does work, it won't last forever (what does?) live for today :D

Oh! I almost forgot, don't yell at me if it makes it worse! Google: dishwash macintosh classic
your kidding right?
 

0ranges

macrumors newbie
Jan 8, 2012
24
0
Mine had only cost 5 bucks. It was also broke! Putting something broken of $5 value in the dishwasher isn't too irrational.. :p
 
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