I recently discovered a ‘secret’ to fixing some computer and LCD monitor issues. Using this bit of information I have fixed a $200 LCD monitor for about $2.00 and on another occasion a computer for about $4.00! I’m sure the same principal would apply to many other electronic devices as well. The secret lies in knowing how to identify a bad capacitor.
The Capacitor Plague
Wikipedia defines the capacitor plague as:
“the common premature failure of huge numbers of electrolytic capacitors of certain brands made from about 1999 and sometimes until 2007, used in various electronics equipment, particularly motherboards, video cards, compact fluorescent lamp ballasts, LCD monitors, and power supplies of personal computers”
In my experience, I had the following issues:
My LCD screen would go blank intermittently, I would turn the power off & on a couple of times, then it would come back to life. This went on for a couple of weeks until one day it would power up but there was no picture, no matter what I did.
The computer that I fixed would turn on, but there was no picture. Hard drives, video card, etc. tested out okay. Then I remembered to check the motherboard for bulged capacitors, sure enough there were two bad ones.
How to Identify a Bad Capacitor
Identifying a bad capacitor is easy, all you do is visually inspect all the capacitors on your circuit board, whether it’s a board in an LCD monitor, a motherboard in a computer, or any other printed circuit board. Good capacitors have nice, flat tops on them; bad capacitors have a bulged top, and sometimes bottom also. Bad capacitors also sometimes sit at an angle or have their bottom seal protruding, and may sometimes ooze electrolyte.
Below are a couple of pics illustrating good and bad capacitors.
Another way to help positively identify a bad capacitor from a good one if it seems like it’s maybe only slightly bulged is to feel the top of it with the tip of your finger, then feel the top of another one. I’ve found my finger can sometimes better feel a slight bulge than my eyes can see.
Once you’ve inspected all your capacitors and identified one or more bad ones, you’ll need to remove the circuit board from your device, then desolder and remove the capacitor(s).
Mark the board on the underside with a permanent marker to make it easier to later find where you removed the cap(s) from. If you are removing more than one capacitor from the same board, be sure to write down or better yet make a diagram so you know which cap goes where.
After removal, measure your capacitors, recording the diameter and length. If you measured in inches, convert your dimensions to mm. You’ll also need the voltage rating (i.e. 6.3v), and the capacitance (the number followed by uf); Both of these specs are printed on the capacitor.
When purchasing a replacement capacitor, use the following guidelines:
The diameter of your replacement capacitor MUST match the diameter of the original so that your leads will line up with the holes on the board correctly, but the length does not necessarily need to be the same. Your replacement could be shorter and maybe even longer, depending on available space when your board is in it’s installed position.
The voltage rating on your replacement can be higher, but NEVER lower.
The capacitance (uf) rating of your replacement MUST match the original.
Polarity is crucial! If you mount the new capacitor with reversed polarity it will destroy the new capacitor, might damage your board, and could cause you injury!
On the capacitor, polarity is marked with a grey band or arrow running length-wise on each capacitor; the grey band designates the lead on it’s side as negative. The positive side has no marking. On the printed circuit board, polarity is usually marked with a plus on the positive side. In any case, it’s best to mark the polarity on the board and/or on your diagram.
Where to Buy Capacitors
If you’re in a hurry to get your item repaired, try checking with your local RadioShack. They had what I needed for my monitor, but not what I needed for the motherboard I later fixed. If they don’t have what you need, they may know of a local electronics or radio shop that will. If you can’t find what you need locally, you can order it from MCM Electronics by clicking below:
Basic computer troubleshooting, soldering and desoldering were all beyond the scope of this post. But for those of you who need a little more info on these subjects, try googling:
I Hope this helps someone out there repair their device! How about you, have any experience with bulging capacitors to share? If so, please leave a comment!
Last Updated: September 18, 2019