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Giza aka Douglas Muth's LiveJournal
My poor iMac 
8th-May-2011 03:47 pm
Leopard White Mage
When I got back from Dorsai Thing a few weeks back, I saw a kernel panic on my iMac, so I tried rebooting it. Upon rebooting it, the screen stayed black and no sounds came from the speakers, nor did the Caps Lock light turn on on the keyboard when I pressed the key. So I took the machine out of service and made a note to open it up at some point.

I finally got around to opening up the machine today, and I found what the problem was:

Blown capacitors

It's quite clear that at least 3 of the capacitors blew out. I'm not clear how this happened, I know that excessive heat can do it but the fans on the system work just fine and there was no excess buildup of dust when I removed the back cover. And I could understand one capacitor failing, but 3 at once? That just doesn't make any sense to me.

Oh well, the machine was old, and served me well for the nearly 6 years that I had it. I'll just stick with my newer machines for now.
Comments 
8th-May-2011 08:47 pm (UTC)
Yeah, that happened to me too. Basically around the turn of the century some cheap Taiwanese capacitors stole a formula for electrolyte fluid which resulted in a buildup of hydrogen within the cells. The end result is that they all started popping their tops a few years later. It's known as the capacitor plague and it was a big scandal at the time.
9th-May-2011 12:48 am (UTC)
Yeah I've seen this happen many times with various pieces of equipment. Crappy caps. Chances are you can "shotgun" all of those filter caps and possibly spare the life of your machine. I've probably saved about a $1000 in electronics/repairs simply by replacing caps blown like these.
9th-May-2011 02:19 am (UTC)
I was about to suggest that :)
9th-May-2011 02:14 am (UTC)
That is sort of a story passed down decade to decade. Its been far too long and the story changes on what country is doing what.

Its more likely a company skimping on parts, or using counterfeit parts (been known to happen.)
9th-May-2011 02:30 am (UTC)
There's some reasonable coverage to back up this specific issue - but yes, the overall message is "don't skimp on parts". That 500W PSU that's as light as a feather probably isn't a good deal!
9th-May-2011 01:54 pm (UTC)
Yep, some companies, especially when pressured to hit specific price points, sometimes do that. It might not seem like much, but 0$.05-$0.20 can be a lot over a whole run.

The big dell lawsuit over the SX lines was over doing that. And they had the gall to claim it was a software issue!

There is a bit more info on this site here about the history, and with different company names. But I agree, its been too long for a case of industrial espionage. More likely today its just bad cost cutting practices.

http://www.badcaps.net/forum/showthread.php?t=425
9th-May-2011 12:12 am (UTC)
They may not have blown simultaneously. Since they're filters for power, you can have them fail in ways (open) that may not stop the machine.
9th-May-2011 01:32 pm (UTC)

That, I did not know. I figured that once a capacitor failed the machine was done for, with possible damage to the motherboard in the process.

That said, it's a 6 year old machine (acquired in summer of 2005), so I'm probably not going to invest the time/money to fix. The G5 chip was underpowered anyway.
21st-May-2011 07:47 pm (UTC)
That's and they're practically dead at this point with the move to Intel. You can't put any newer MacOS on it than 10.5, and I think some apps now are starting to be written for Intel only - so eventually you'd run into compatibility issues with older web browsers, etc.
9th-May-2011 01:10 am (UTC)
Looks like a simple enough fix. I've done it myself on several PC motherboards.
9th-May-2011 01:47 am (UTC)
Assuming that's all that's broken, it's an easy fix.
9th-May-2011 01:34 pm (UTC)

As I've learned! :-P

As I stated elsewhere though, it's just not worth the time/effort for me to fix a 6-year old underpowered machine. I could use the desk space, anyway.
9th-May-2011 01:54 am (UTC)
Is this the one that was streaming YouTube to the tv that one time?

...because, if so, I think maybe it was magically friendshipped to death.
9th-May-2011 01:35 pm (UTC)

No, it's the one that was sitting on my spare table.
9th-May-2011 03:52 am (UTC)
I had an Athalon XP board that failed where nearly every capacitor had expanded.... I might still have that board too...
9th-May-2011 04:21 am (UTC)
Same thing happened on a video card last month for me. Likely one of those capacitors started going a while ago, and it took three gone before it stopped working.
9th-May-2011 04:41 am (UTC)
Yep, its not a hard fix if you have a good soldering iron and a spare $20 to digikey. You just have to choose good Cap brands, and not bad ones.

I can't see what brand they are, but they have coloring kind of like Panasonic, but not the tops.

Capacitors can often fail in a block like that, its common. If you want to try, you would be best to replace ALL of those, as when one starts to fail, it will generate excessive heat and cause others nearby it to fail too.

I can see they're 6.3v 1800uf, so that would not be too hard to find. Don't get Radio shack if you do. They're garbage. Definitely you want low ESR caps. Check the size of them, the biggest problem I have found is getting replacements of the same size.

If you are interested in a resurrection project, I would go read up on www.badcaps.net forums. Hell, they often get a lot of people talking about common brands, common failures of models, etc.. not a bad place to see what brands are using cheap and which are not.
9th-May-2011 04:40 pm (UTC)
Actually, they don't. One or two will blow out and the circuit can still function. By the time you've lost enough that the computer quits, you've got a group gone bad.
9th-May-2011 04:53 pm (UTC)
They can fail without any physical signs of failure. The ESR can go to crap without them bloating or popping. The only way to be sure is to dig them out, and test them with an ESR meter.

Still, its a good idea to just replace them all. One bad one can cause others to die out faster.

Hence, its better to replace them all. When they cost so little to replace, its not a big cost.
9th-May-2011 04:54 pm (UTC)
Absolutely!! If you are replacing one, replace them all. And with Tantalums if possible to eliminate the drying out problem.
9th-May-2011 05:14 pm (UTC)
Interesting. I had been reading up for a while, had not come across these yet. Mostly on Poly and a few ceramics...

at first glance they might not look too good for MBs, because of a higher than usual ESR. Maybe not used RIGHT next to the VRMs, dunno. I would have to read up more.
9th-May-2011 11:00 pm (UTC)
You're quite right, the tantalums just wont hack it. Good quality low ESR Japaneese caps, prefrably from Nippon Chemicon.. they make arguably the best caps in the world
9th-May-2011 01:33 pm (UTC)
Looks like four or five of 'em to me, in that photo. I notice the ends are trimmed so the caps are more likely to blow out that way instead of bursting their sides.
9th-May-2011 04:39 pm (UTC)
The electrolyte gets hot from the million times a second charge/discharge of a switching power supply. Finally, they are dried out and go foom. Average time to fail - 4 years.

Which is why we don't use them at ALL in avionics. Tantalums pretested to weed out the shorted ones are what we use. Find a place that can replace them and hand the tech some tantalums to go in place and the computer will easily last another decade or two.

Notice how old electronics didn't have this problem? You could find a mid 70s tv and it would still function? Because they weren't given such hard driving jobs like switching power supplies back then. Today, buck convertors to efficiently convert 5V 10A to 1.2V at 41A really push electrolytic caps to the wall.
9th-May-2011 05:04 pm (UTC)
Some of the people doing replacements of Electrolytics do "poly Mods" using solid state polymer capacitors, they have a much longer lifespan and are more resistant to heat. That is why I look over motherboards to see what kind of caps the are using, you can tell the cheap ones from the good ones.
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