Macintosh Classic II checkerboard display

[cppursell]

Hi. I just got my hands on a Macintosh Classic II, shipped to me for free from a guy who said it worked fine.

I plugged in the keyboard, mouse, and power, and flipped the switch, and voila! A nice black and white checkerboard on display. I restarted it many times, and it mainly sticked with the checkerboard, but occasionally went to thick vertical lines, and only a couple times showed a white screen. It also occasionally emitted a quiet, but high pitch noise.

I opened up the computer (thank God I had a torx screwdriver that fit) and cleaned the contacts on the RAM as suggested from another forum: didn't work. What now? I'm hearing advice such as "replace the capacitors" to crazy stuff like "wash the motherboard in the sink". I REALLY want to have this classic Mac to play with; but is it doomed to become a Macquarium instead?

Thanks ahead for your valuable help.

 

[iMac600]

Replacing the Capacitors will fix it for good, washing it in the sink will remove the electrolytic fluid that has leaked from said capacitors. It does conduct, so it bridges the traces and causes the aforementioned problems.

Most electronics repair shops should be able to replace the capacitors if you can't yourself.

 

[cppursell]

Okay, I'm guessing I can go to an electronics store or Radioshack to get some capicitors, but I have no clue what to get, or which ones to replace, can I get some help in that area?

 

[Hulotte]

Well "wash the motherboard in the sink" is not a so crazy stuff.

I made it a few days ago with a classic II that was only showing vertical black and white stripes.

And.... now, it works !!!

 

[tomlee59]

Whether or not you replace the capacitors, you still need to wash the board. And although it does sound nutty, a dishwasher is a perfectly fine device for doing exactly that.

The capacitor-replacement expert here is probably JDW. But until he chimes in, I'd say that a good choice is a tantalum capacitor. Modern ones have no liquid electrolyte, so you wouldn't suffer a repeat in the future. The exact capacitance is wholly unimportant (almost all of them are just "shock absorbers" connected across the power supply terminals). Just don't go lower than, say, 25% below the original capacitance value. Also, make sure that the voltage rating meets or exceeds that of the capacitors you are replacing.

If you've not done this sort of operation before, it's a good idea to practice first (say, on a junk PC card or board). Once you've gotten confident in your ability to remove a capacitor without destroying the pc board traces, you'll be ready for the real thing.

 

[cppursell]

Okay, I can get the capacitors at Radioshack. As for washing the board, I just want to be a little careful: Should I use detergent? The dishwasher uses hot water, is that okay? When drying, should it be room temperature air dry for a week or so, or speed dry it in the washer?

Last but not least: which board? There's a green one that has the RAM in it laying horizontally, and a tan one standing up on the side that I see at first glance. And, where exactly are the appropriate capacitors to be replaced?

Thanks again

 

[equill]

A dishwasher is indiscriminate in where it squirts liquid. A rescuer of a Compact AIO does better to use a spraybottle, which can be varied from an intense jet to a misting spray, and thereby also directed to badly affected spots. The whole board should be washed, certainly, with clean warm (40-45°C) water containing a few drops of a non-ionic (most kitchen detergents are so) detergent in a pint or so, and then liberally washed with clean warm water.

Blot the surplus moisture off the board with a paper towel, and then set the board aside (vertically, to assist drainage) for several days, or leave it in a draught, to dry completely before further work is done on it. One essential inspection then is against corroded or broken board traces. Only if the board is physically intact is the effort of recapping going to reward you.

de

 

[tomlee59]

Last but not least: which board? There's a green one that has the RAM in it laying horizontally, and a tan one standing up on the side that I see at first glance. And, where exactly are the appropriate capacitors to be replaced?

Thanks again

The logic board is the one you want to fix -- it's the one with the RAM, and you should be able to see smudges of residue from the leaking capacitors. It is usually fairly obvious. The capacitors in question are the ones by the smudges, as well as the others of the same type.

Whether you use equill's more refined washing procedure or the "scorched earth" dishwasher method, you'll want to remove the RAM simms first.

 

[Hulotte]

Whether you use equill's more refined washing procedure or the "scorched earth" dishwasher method, you'll want to remove the RAM simms first.

Yes and also the ROMs should be removed before washing. That's what I did.

 

[equill]

Not all Mac ROM chips will co-operate in being removed (as is often the case in a Classic II), but if they are on a card (as in an SE/30), your suggestion is worthwhile, if only to make drying the MLB thoroughly so much easier.

de

 

[cppursell]

Okay, I've taken out the green motherboard with the RAM in it, but I'm not sure where the capacitors are; can you point them out to me? Here's a link to the two boards in question, the green board with the RAM, and the tan board standing on the side:

http://gallery.mac.com/cppursell#100081

 

[equill]

You are looking for 3 x 47µF/16V, 2 x 1µF/50V and 12 x 10µF/16V caps, most of them in the rear half of the MLB. They appear as (mostly) bright circles in your left-hand pic., and as little vertical cylinders on the board, with a number prefixed with 'C' screened onto the board near each one. C74, C79 and C106 are in the front half of the MLB.

This post gives you some idea of the replacement process and a potential source of replacement caps (tantalum electrolytics).

If, however, you are as unfamiliar or uncomfortable with the whole notion of replacement as you seem to be, you may wish to explore having someone else do it for you.

de

 

[cppursell]

Okay! I washed it in the dishwasher, then blot dried it, and now it will sit upright peacefully for a week!

I went to the electronics store to get replacement capacitors, and found it to be a little too expensive for this project ($25). I just hope that the existing ones will work for the time being. Besides, I think it would be a long, daunting, frustrating task to replace 13 capacitors. Oh, the store can do it for me, for only $150 an hour...

Thanks for your help and advice. I'll let you know if the washing technique worked. For now I'll just be stuck with my other computer... my Macbook Pro .

 

[cppursell]

The computer works now!

I couldn't wait a week, I just let it finish drying overnight, probably not a wise thing to do.. but it worked.

I have an 80mb hard drive, and 4mb of ram. Cool!

I posted a thread asking this, but I can ask here too: Where can I find some applications and games for this machine (like a website)?

 

[equill]

Good to hear that it is working for you. Just keep in the back of your mind, though, that will fail again at some time unless the caps are replaced. Foe me, a recent Classic took only 10 days or so from checkerboard to checkerboard via the spraybottle. However, that was long enough to get from System 7.1 to 7.5 and back to 7.1.3. 68000 processors are easily intimidated, but your 68030-driven Classic II can give you much good service.

For software there is a hot place nearby (rather than down below), and those who know of it will direct you.

de

 

[Mac128]

cleaned the contacts on the RAM as suggested from another forum: didn't work.

Are you sure they said RAM?

The checkerboard problem is common on the SEs and Classics. The solution is usually to re-seat and or clean the ROM connections, not the RAM. The M0001s had similar vertical stripes related to ROMs as well.

Washing the logicboard likely resulted in a similar effort and/or water trapped in the sockets is actually enhancing the connection. Once the board thoroughly dries, you may once again get the pattern. Either way, you are luck your impetuousness didn't short out the whole board.

Granted this was the prescribed procedure 15 years ago before those caps started leaking all over the place. Nevertheless, try cleaning those ROMs if you didn't. Why Apple decided it was a good idea to go from 2 to 4 ROMs is beyond me. The Classic only has one! Was it a counterfeiting countermeasure moving to so many ROMs?

 

[cppursell]

I'm pretty sure the ROM wasn't the problem, and the capacitors are still bad, I can sometimes hear them whining. I'm sure the computer will eventually fail again, and then at that point I'll decide whether replacing the capacitors will be worth the effort.

 

[tomlee59]

I'm pretty sure the ROM wasn't the problem, and the capacitors are still bad, I can sometimes hear them whining. I'm sure the computer will eventually fail again, and then at that point I'll decide whether replacing the capacitors will be worth the effort.

Yes, it's neither the RAM nor the ROM. After having fixed countless of these things, I can say with confidence that it is very rarely due to a memory contact problem of any kind. Since it's easy to check, doing so is the first thing to try, but washing the board and replacing the capacitors is the way to solve the problem in nearly every case. No speculation is required -- a simple visual inspection will reveal whether the capacitors are leaking.

The SE, SE/30. Classic and Classic II all suffer widely from this malady; the original compacts do not. I don't have enough experience with the Color Classic/II to say whether this problem affects those models, too.

 

[Mac128]

I'm pretty sure the ROM wasn't the problem, and the capacitors are still bad,

Yes, it's neither the RAM nor the ROM. After having fixed countless of these things, I can say with confidence that it is very rarely due to a memory contact problem of any kind. ...

The SE, SE/30. Classic and Classic II all suffer widely from this malady; the original compacts do not. I don't have enough experience with the Color Classic/II to say whether this problem affects those models, too.

Tom, I don't doubt this is the case, given your experience. However, I'm not sure how a problem can be dismissed without checking, especially since all the repair guides I've read indicate this as a likely problem. In particular, I received an old Classic II from eBay a few years ago, advertised as being in a closet, with no power cord, keyboard, etc. to test. When I got it, it did not boot up and displayed a checkerboard-like pattern. I consulted Pina's SE & Classic Macintosh repair book and he described re-seating and cleaning the ROMs. That was all it took and the thing booted right up and runs fine today. None of the repair books of the day mention a word about leaky caps, which obviously wasn't a problem then as now.

For cppursell, this is moot.

Now, in a related issue: I completely understand that the Classic & Classic II would suffer this problem identically given their similar logicboard designs and as I have pointed out before, the first compacts to use entirely surface mount technology. What I don't understand is how the SE & SE/30 can exhibit the exact same symptoms, while the M0001 logicboards don't given that they are the exact same technology construction-wise, particularly the SE, which uses what appear to be identical capacitors in a similar ratio as the Plus. If the caps don't leak on the Plus, why the SE? It's more understandable with the SE/30 which at least uses SMDs similar to the Classics.

As for the Color Classic, I have never seen an SMD related issue. Though Stuart Bell over at Applefritter would be the guy to ask.