Hey, Jim, just read in a German NG where someone had the same symptoms. Thought is was the RAM modules, had them tested by a shop, RAM was fine, took a really good look at the mobo and saw that some caps had begun a slight bulge. Might be worth a look if this happens again on the affected PC.
-- Regards, Joerg http://www.analogconsultants.com/
Thanks, I'll take a closer look.
...Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |
It's been going around for several years now - cheap non-OSCON high-density caps with inferior substitute organic electrolytes. One doesn't always see a bulge; often the most reliable symptom is CPU crashes. It's generally taken that the fix is a new mobo.
Most of the time, it's cheaper than trying to replace all the caps. normally, all the caps are of the same vender and if one starts going, the others might not be to far behind. I understand how ever, that a couple of the chinese manufacturers did have problems with crappie caps and no longer are using them.
Could be hear say, who knows.
-- "I\'m never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5
All mothermakers during around '99-'02 had problems with those caps. They came from a single manufacturer and showed up *everywhere*. I've personally seen the problem on motherboards from asus, msi, intel, gigabyte, ecs, and biostar. I don't think any correlation between the use of the bad caps and the maker's nationality.
Eh? The fix is to change the caps.
It can often be diagnosed by holding a scope probe to the rails. If you see excessive spikes that would be the tip-off. And yes, changing the caps might be a bear to do. You might occasionally strip the metallization out and Murphy's law states that this is usually going to happen on the last one. Obtaining caps that fit the available space can also be a (pricey) adventure.
-- Regards, Joerg http://www.analogconsultants.com/
Winfield hath wroth:
I've been fighting that problem for years. For a time, I was replacing ALL the caps on motheboards. I have a Pace desoldering station so that was fairly easy. Some motherboards have fairly sloppy hole clearance for the capacitor leads, so removal and replacement were easy. Others (i.e. Dell) looked like the caps were pounded into the motherboard. If I ripped out the plated through hole along with the capacitor, it usually indicated that I just destroyed the board.
The first indication of trouble is usually the rubber plug on the bottom of the capacitor trying to wiggle out of the can. If the board has a number of lopsided caps, it's either the worlds sloppiest board manufacturer, or the caps are about to go bad. Usually the rubber plug shows before the top or sides bulge.
I've tried various methods of detecting bad caps. Bulges aren't always a good indication. I have an old Dick Smith capacitor ESR tester, which is easily fooled by the large number of parallel capacitors. It works fine if the capacitor is independent or pulled, but not on the motherboard power supply bus.
I've also tried far IR imagers. Nothing like $20,000 worth of borrowed hardware to repair a $100 motherboard. Some digital cameras can see near IR and don't work for seeing heat. That has found some overheated capacitors, but more often just shows the reflected radiation from the CPU. A finger test of the capacitors is sometimes effective. If the cap is warm, it's bad.
I've tried to use a scope to detect the expected noise on the power supply lines, with little success. All motherboards have some noise on these lines. The point of measurement (and grounding) have a huge effect on this noise level. Making an accurate determination is difficult.
The degree of failure is also somewhat entertaining. I've seen motherboards with severely bulged caps, that continue to function without incident for many months. Eventually, there's a failure, but the amount of damage these can tolerate are amazing. On the other foot, I've seen boards with only a barely visible amount of bluging, generate boot problems and crashes. I suspect that this is an indication of board quality.
For motherboards that I just wanted to work, and didn't care what they looked like, I just chomped off the capacitors with a pair of very large cutters, leaving the leads in the mother board. I then tack soldered the replacement capacitors leaving about 1/4" of leads exposed. It looks truely unprofessional, but gets the job done without destroying the motherboard. I've also substituted tantalum caps for the low-ESR electrolytics. Although more expensive, the low frequency ESR is less, so fewer caps can be used. Please don't tell anyone I suggested doing all this.
Drivel: See comments on tantalum ESR at:
in the "using the meter" section. I've seen the same problem with the same caps. If you think we have problems with low-ESR electrolytics, get ready for more of the same with tantalums.
In retrospect, it's not worth fixing the motherboard. It's just too much labour. If it's under warranty, get a replacement. If not, buy a replacement and install it yourself.
Incidentally, I've seen some random CPU's fail along with the motherboard when run with volcanic capacitors. I haven't investigated the connection, but I suspect that non-optimum power supply voltages and substantial voltage spikes, might not be very good for CPU survival. In general, the ones that crash while booting or running will have this problem.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Just got done fixing two Sceptre LCD monitors bought in 2004. Both died close to the same period, about 1.5 years later. Multiple bulging electrolytics on the outputs of the low voltage switching supplies were the culprit. I've also seen a oozing capacitor on a View Sonic monitor cause problems. That was the cap on the output of the mains rectifier.
Mark
That works much better if you build yourself a little toroid transformer so you can measure differentially. Done that at a client on Tuesday. Then I needed one that goes down to a few Hertz so I took a large iso transformer. You should have seen the face of one engineer walking in on us and seeing a mains plug going to two 1N4148 and then on into the soundcard input of my laptop. Sure enough that also had to be the day the fire marshall did his rounds. I quickly tossed a rug over all that ...
With Windows that sort of crashing is kind of normal.
-- Regards, Joerg http://www.analogconsultants.com/
Perhaps some MLCC (high capacitance ceramics) in parallel to the leaky caps may do the trick.
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Depends on how many coals the switcher in front of it can throw on the fire because a few 1uF or 10uF MLCCs can only supply juice for a few usec.
-- Regards, Joerg http://www.analogconsultants.com/
When those electrolytics leak, they eat the traces off the PC board.
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