Got Bad Capacitors? Here’s What to Do!

FIVE bad capacitors are what got a Condor power supply grounded! Output voltage reduced to zero! Our customer had fallen victim to one of the most failure-prone components in a power supply: the electrolytic capacitor.

Staying informed on the facts about  bad capacitors is IMPORTANT to protecting your power supply and your other critical electronic assets! The two primary items that are affected by bad capacitors are Drives and Power Supplies. All Drives and Power Supplies use Electrolytic Capacitors in some part of the unit!

Here are some things to know about bad capacitors:

Aluminum Capacitors (especially electrolytic, unlike ceramic or film), are highly prone to failure.

They are part of a family of capacitors that are polarized. They have a Positive lead (anode) and a Negative lead (Cathode). If the voltage is reversed, polarized capacitors can fail. When this happens, the shell explodes! Capacitors can ALSO fail if their voltage exceeds their rating. Increased voltage can damage the capacitor if is too far above the rating. Increased voltage can also cause damage if it goes on for too long a duration.

Aluminum Capacitors are one of the few electric components that use liquid to operate.

This means that exposure to excess heat can cause them to fail quickly. This heat-induced malfunction is commonly called “thermal aging”.

power supply repairsHeat results in the liquid electrolyte evaporating, reducing the capacity to hold a charge.
  1. 1.  Exposure to excessive heat will greatly reduce the life span of electrolytic capacitors. Sitting unused will cause the capacitor to dry out significantly.
  2. Then, when the electric current is turned on and the heat reacts with the chemicals in the capacitor, it will begin to bulge. This means the capacitor is now damaged.
So the question now is:   What steps can YOU take to prevent capacitor failure?

One of the important things to consider is: the location of your power supply. If it is outside, then you need to be aware of the heat that is being generated by the sun. This can add to the heat already generated by the machine itself!

Consider these factors when determining heat load:
  • Total surface area/volume of the enclosure
  • Color of the cabinet (DARK colors will absorb more heat!)
  • Internal heat created by equipment
  • Ambient temperature (temperature around where the power supply is located)
Another important factor to consider is: DERATING

Derating is essentially the temperature threshold at which a power supply can be heated to before failing. If your power supply is running in an area that is always hot, you will need to cut back the rated power. This will prevent excess damage being done to the capacitors! A derating curve can tell you what the trade off is, and how to use that information. You can contact your manufacturer to get this information.

If the solution to excess heat could be summed up in a word, it would be: AIR!
  • Using industrial fans inside your machine enclosure can reduce heat by 10% and often more, which will add up over time. NOTE: setting up a floor fan and aiming it at your power supply is extremely inadvisable. This is a dangerous setup and will conflict with OSHA regulations.
  • Compressed air cabinet coolers are a more expensive option. Compressed air cabinet coolers are a more expensive but effective option. These will cool the cabinet as needed.
Cooling your power supplies is ESSENTIAL to preserving the life span of your capacitors and other electronic equipment!

If it is too late and your capacitors have already suffered heat damage, check to see if your equipment is under warranty. If it is still under warranty then contact your OEM to see about repairs. If it is no longer under warranty, then contact your trusted repair center to get your equipment back up and running. If you do not have a trusted repair center, try this handy Repair Guide.


About the Author: ACS Industrial Services is an independent industrial electronic repair center providing repairs for all types of industrial electronic equipment and most all manufacturers including circuit board repairs, logic board repairs, industrial power supplies, repairs for variable frequency drives, servo motors, CNC equipment, encoders, monitors and touchscreens, test equipment, light curtains, and much more.  Rush Service is available and a comprehensive 2-Year Warranty covers most repairs.  The customer service team is available to answer your questions and help solve your industrial electronic repair problems. You can reach them by calling 800-605-6419 or going to