Macintosh Classic II checkerboard display

[tomlee59]

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.

Sorry that what I wrote was unclear. I meant to emphasize that since it is so simple to check ROM/RAM that one should certainly do so. We are in total agreement here. That said, capacitor leakage is a far more likely cause of this symptom, although certainly not the only one. It is just that memory sockets are not that bad, and there is certainly no reason why the classics should suffer inordinately from such a problem.

 

[equill]

... 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.

http://68kmla.org/forums/viewtopic.php?t=3277

de

 

[Mac128]

I'm not sure how a problem can be dismissed without checking.

Sorry that what I wrote was unclear. ... It is just that memory sockets are not that bad, and there is certainly no reason why the classics should suffer inordinately from such a problem.

No you were clear ... I meant for someone who does not have your experience diagnosing hardware problems. On threads like this, for future use, I like to emphasize trying the easiest things first – not that anybody actually searches these forums for info. In particular our friend demonstrated the dangers of throwing a board into the dishwasher, by not waiting as long as he should have for it to dry. While I've no doubt of the procedure's value, failure to follow simple directions in such methods can be devastating. Anyway, my experience with re-seating RAM & ROM is that many of these old Macs have been stored in places that encourage corrosion, or the same heat expansion that doomed the Apple ///.

One interesting side note regarding how bad the sockets are ... Pina goes into some detail about the Classic ROM socket. Evidently Apple took the low-cost philosophy down to the smallest part: he claims these sockets only have contacts on one side of the pin. Later Apple switched to the more robust variety which made contact with both sides of the pins. This is one reason the Classic in particular suffers from the checkerboard pattern. If that's true, given the capacitors propensity from this era to leak, compared to their older cousins on the Plus, who knows what kind of alloy the metal contacts on their cheap sockets might be made of or how likely it is to corrode. Not that this is the case here, just thought it interesting to note here.

equill, thanks for that refresher link. Interesting that cap goo hath flooded your logicboard like the Red Sea following Moses' passage, yet demonstrated no deleterious effects in powered use.

An interesting study would be spelunking through the depths of Apple confidential repair records to determine the frequency and cause of the majority of repairs of a particular Mac from the period and what lessons Apple took from it to effect future changes in parts or design.

 

[tomlee59]

Again, to be clear, we do not disagree on the sequencing. That's exactly why I said nothing when you first advised to check the ROMs. It's only AFTER he experienced what I'd silently expected to be a null result that I chimed in. That was not an accident on my part. I waited until he reported on the outcome of Step 1.

So, by all means, having a person check the ROM/RAM as a first step is the smart and easy thing to do. In most cases involving the later compacts, however, that will not fix the problem. Just as easy is to see whether there are telltale smudges around the capacitors. That's why I chimed in with Step 2. And anyone advising someone who is troubleshooting this problem should mention the capacitors because they are a known cause of the largest fraction (by far) of these symptoms. Yes, I've seen a couple instances of bad sockets, but I've seen vastly more instances of leaking caps. So, in my experience (yes, it's a limited sample, but at this point, I'm willing to declare that my sample size is much larger than most people's), the statistics support a focus on the capacitors. Sure, many other faults could cause the symptoms in principle, but it's the capacitors that typically do cause the symptoms in practice.

 

[Mac128]

Again, to be clear, we do not disagree on the sequencing. That's exactly why I said nothing when you first advised to check the ROMs. It's only AFTER he experienced what I'd silently expected to be a null result that I chimed in. That was not an accident on my part. I waited until he reported on the outcome of Step 1.

To be clear, neither am I! And thus the dangers of posting on multiple forums. cppursell mentions nothing about capacitors on this forum and only said he checked the RAM SIMMs NOT the ROMs. Obviously there was more to his evaluation going on on another forum, to which you must have been a party. As always Tom, you exercise much restraint and a clear procedural aptitude along with your years of experience. I am certainly not questioning YOUR participation on this thread. Just trying to be clear about what I missed on another ...

Speaking of experts, it is surprising JDW has not weighed in on this one.

 

[equill]

Perhaps JDW was busy stirring another broth, somewhere? Even one for the delight of his household rather than his fellow soldiers?

Your point about potential confusion as a result of double- and out-posting is well made.

de

 

[trag]

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.

Ah, sounds like I need to add a spool of 10 uF caps to my collection. I've been too busy too actually pull out my 68K Macs and examine the logic boards, but my memory told me that the IIci uses a few 10 uF caps. Yet, Gamba's page about the SE/30 noted a 1 uF cap, so I guessed that my memory was off by a factor of ten. I guess they were both right and some machines use the 10 uF caps. I wish I had pulled one of the IIci's out and checked a few weeks ago. I had a chance to pick up a spool of 10 uF tantalums pretty affordably at the same time I got the 47uF and the 1 uF.

 

[rogerw]

The suggestions in this thread worked for me. A 17 year old Classic was revived by soaking the main board in a pan of distilled water for about an hour, rocking the pan gently for a few minutes at the end. Air dry overnight.

The SMT replacement caps were bought at Halted Specialties in Santa Clara, CA. Heat the top of the old cap with a soldering iron and pull the body off, leaving its leads still soldered to the board. Each lead can then be desoldered without damaging the underlying trace.

Thanks for the info. This Mac has been in use all these years, the last 15 with a Mobius 030 accelerator.

 

[lostcluster]

I know this was an old, thread but I too had the checkerboard pattern on my Classic II. I cleaned the Simms and slots, same pattern. I then removed the four IC's and cleaned those too with Isopropyl Alchol..same thing. I cleaned the board (I thought) with contact cleaner, nope still there. So I look on the internet and found people have washed the motherboard in the dishwasher/sink and it corrected the problem, NO WAY I thought! YES WAY!!LOL I removed the simms and the 4 IC's and put enough hot water and dish soap in the sink to cover the board and proceeded to scrub the board with a toothbrush (tip... do not use the wife's toothbrush if she frequents the kitchen to refill her coffee cup!) I cleaned the board top and bottom and concentrated around the groups of capacitors. I then patted dry and used compressed air to speed up the drying process. I Installed the motherboard, pressed the power button and voila! I would not have believed it if I did not try everything else first. I will replace the capacitors at a later date. Thanks for helping me get on of my old macs alive again!!

 

[SusanMKim]

Thanks to all the advice on here. I had an old screenplay on my mac classic. I had not turned on the mac in eons and was greeted by the checkerboard.

Here's my advice:

1. Clean around the capacitors with alcohol (it will evaporate faster).

2. The good news--- it works! The bad news-- if you turn off your machine-- it may go back to the checkerboard and you'll have to do the whole process over (in my case-- 10 TIMES before it works again)

3. My suggestion: If you are trying to use your old mac to get some old documents, screenplays, info-- whatever--- keep the machine on and get the info while you can. Assume this may be your only chance to get the info-- so type/write down the info if you can't download it.

Other advice to total non-geeks like myself--- the advice on these boards sounds more complicated than it is-- it's pretty easy. The hardest part is finding the right screw driver to open the machine. Search images if you're not sure what the capacitors look like.

 

[techknight]

if found that if i tried heating the body of the capacitor or just 1 lead at a time, it eventually tears the pad off the circuit board.

What i use to avoid it, is CAREFULLY heating the board up with a heatgun. careful, meaning dont blast it everywhere and melt all the plastic. Once the board is preheated, you can take the gun and focus it on each individual capacitor and itll melt the solder faster and remove it. or if you pre-heat the board hot enough, you can use a soldering iron and remove it without damaging pads and traces as the preheated board will allow the solder to stay molten longer. giving you time to heat the other side with iron and then remove with needle nose/tweezers

i used to do alot of hyper modules and old sony handycams this way.

 

[trag]

if found that if i tried heating the body of the capacitor or just 1 lead at a time, it eventually tears the pad off the circuit board.
What i use to avoid it, is CAREFULLY heating the board up with a heatgun. careful, meaning dont blast it everywhere and melt all the plastic.

A heat gun can be useful, especially when desoldering larger chips with many leads. One way to avoid blasting surrounding components off of the board is to cover them with some modeling clay. A package of modeling clay will last you for a lifetime of soldering (unless you do an amazing amount of desoldering). Keep it in a ziplock bag so it doesn't dry out.

All that said, really, the easiest way to desolder surface mount capacitors and resistors without damaging the traces, pads or board is to use *two* soldering pencils simultaneously. Apply one to each pad of the component and wait until it will gently lift off of the board.

Just go to Radio Shack and buy their 15 watt soldering pencil with grounded tip as your second pencil. It's $8.99, which isless than $10. It may be lower quality than most folks want as a primary soldering tool (it is my primary soldering tool; I have two of them) but you can get one as a second pencil for when you want to desolder caps and resistors. If one is outside the USA I'm not sure where one would go for an inexpensive serviceable pencil but there's probably an equivalent.

 

[techknight]

yea there are many solutions, its up to the guy who started this thread to decide which route to take ;-)