Full story at http://en.wikipedia.org/wiki/Capacitor_plague

 

I come across this all the time in the pc repair world at least 1 in 3 older pc about 2-3 years old 

While the capacitor plague has affected large numbers of desktop computers, the problem is by no means limited to that category. Bad capacitors can also be found in external power supply adapters, network switches, audio equipment, flat panel displays, and a wide range of other devices. Bad capacitors can cause a simple failure to turn on, or a wide range of bizarre (often intermittent) behavior of afflicted electronic equipment.

 

 

The capacitor plague was a problem with the higher than expected premature failure rate of aluminum electrolytic capacitorswith non-solid or liquid electrolyte of certain brands, especially from some Taiwanese manufacturers.^[1] The capacitors fail because of a special water based corrosion effect, due to a poorly formulated electrolyte.

 

Direct visual inspection is a common method of identifying capacitors which have failed because of bad electrolyte. Failed capacitors may show one or more of these visible symptoms:

• Bulging or cracking of the vent on top of the capacitor.^[3] (The "vent" is shaped by an impression stamped into the top of the can, forming the seams of the vent. It is designed so that if the capacitor becomes pressurized it will split at the vent's seams, relieving the pressure rather than exploding.)
• Capacitor casing sitting crooked on the circuit board, as the bottom rubber plug is pushed out.^[3]
• Electrolyte leaked onto the motherboard from the base of the capacitor or vented from the top, visible as crusty rust-like brown deposits.
• Detached or missing capacitor casing. Sometimes when the vent does not open, a failed capacitor will literally explode, ejecting its contents violently and shooting the casing off the circuit board.

Sometimes, electrolytic capacitors fail without any visible changes in appearance of the external SMD or metal can package. Since the electrical characteristics of capacitors are the reason for their use, these parameters must be tested with instruments to definitively decide if the devices have failed.

Electrical symptoms[edit]

As an electrolytic capacitor ages, its capacitance usually decreases and its equivalent series resistance (ESR) usually increases. The capacitance may abnormally degrade to as low as 4% of the original value, as opposed to an expected 50% capacity degradation over the normal life span of the component. When this happens, the capacitors no longer adequately serve their purpose of filtering the direct current voltages on the motherboard, and a result of this failure is an increase in the ripple voltage that the capacitor is supposed to filter out. This results in a system instability. Capacitors with high ESR and low capacitance can make power supplies malfunction, sometimes causing further circuit damage. In computers, CPU core voltage or other system voltages may fluctuate or go out of range, possibly with an increase in CPU temperature as the core voltage rises.

 

Failed capacitor images

Opened electrolytic capacitor with extracted foils partly unwound. Red color is typical for some water-based electrolyte chemistries. 

Unwound layers of a failed electrolytic capacitor; foils are glued together, typical construction with water-based electrolytes. No obvious damage (short circuit) is visible. 

Failed electrolytic capacitors with swollen can tops and expelled rubber seals, dates of manufacture "0106" and "0206" (February 2001 and June 2002) 

A blown capacitor (top center) only can be viewed as evidence of a "bad" one with wrong electrolyte, if it can be shown that the capacitor has failed "prematurely" 

 

All these aluminum electrolytic capacitors have failed, with open vents in the top of the can, and visible dried electrolyte residue (reddish-brown color).

 

Edited June 20, 201411 yr by rss3781

Seriously though, almost nobody here is going to know what to do with that information, though it's appreciated. You'd likely need soldering knowledge and a trained eye for small circuit board failures to do anything about it. And while busted caps can sometimes be visible on the motherboard itself, I highly doubt anybody is going to crack open a device such as a power supply to go look for a problem that may or may not be there. For most folks here, I'd advise you to just replace the part if you're worried about it.

Edited June 20, 201411 yr by unr3al

JUST CHECK THIS In computers, CPU core voltage or other system voltages may fluctuate or go out of range, possibly with an increase in CPU temperature as the core voltage rises.

YES I AM OLD SCHOOL first computer 1991 33mhz 200mb harddrive IF U THINK YOU HAVE A BAD CAP TAKE A PIC AND SEND IT TO ME ITS NOT THAT HARD TO TELL

if u find a bad cap on your mother board GET A NEW ONE DONT TRY TO FIX IT AND NEVER EVER OPEN A POWER SUPPLY CHARGED CAPS ARE NO JOKE

Edited June 20, 201411 yr by rss3781