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Why does a fuse blow?

First off we need to understand what a fuse is. A fuse is a safety device, primarily designed to protect something from fire or damage. A normal fuse is simply a small wire running from one electrode to another electrode and encapsulated in some kind of fire proof casing.
A fuse should not be confused with a circuit breaker. A circuit breaker has the same purpose as a fuse, but it can be re-set and used again. A fuse has to be replaced when it blows.
Fuses, especially ones found in a television, can be very deceiving and hard to find. They come in many shapes and sizes. Other components like; resistors, or coils, may also do double duty and act like  a fuse. This behavior is engineered into the component.

A fuse under normal conditions will allow the free flow of electricity to the circuit it is feeding. Normally, if everything is working correctly, the fuse has absolutely no effect on the circuit. If the circuit that the fuse is feeding draws too much current, the fuse wire will get very hot, very fast, causing the wire to disintegrate or burn open in one spot.  Once that wire has been broken, no electricity can pass through to the circuit beyond.
It is extremely rare that a fuse will blow without another problem causing it to blow. After all, that is its purpose. It is designed to blow if something else is wrong, especially in a TV or other appliance. If a fuse is blown in a TV, expect that you will need to fix it.

Most of us are used to dealing with fuses, or breakers, in our house. By replacing the fuse, we usually make it all better again. But when you think about it, the fuse only blew because you had the bathroom heater turned on at the same time you had the blow dryer turned on. So you overloaded the circuit. Again, you had to fix something to keep the fuse from blowing, like turning off the heater while you were blow-drying your hair. Replacing the fuse did not fix the problem. Turning off the heater fixed the problem. The fuse was a symptom of the problem. Inside the television you have no control over how much power is being used. So the reason that fuse blew is inside the TV it’s self.

 Power surges from lightning or power line transmission problems can cause a fuse to blow.  The abnormal voltage and current flows in this situation will usually do more damage to the TV, but in some rare cases the fuse is all that has blown. If an internal fuse has blown, it always has to do with a problem in the television.
When you replace the fuse, use the same amperage, because increasing the amperage does not help, it just allows the circuit more current, possibly causing a fire. If the circuit keeps blowing a fuse, you have a problem that needs to be addressed and resolved. Don’t mask a problem by trying a higher amperage fuse. This will only make your problem worse.

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I see technology only after the chalk outline has been drawn on the floor. Follow me through the word of repair and learn the gritty truth about technology.

Discussion:    Add a Comment | Comments 1-6 of 6 | Latest Comment

March 5, 2008 5:19 PM

Hi, I've downloaded the service manual and performed a self diagnosis test. The results were: AKB 1 and HV 1, also the Standby light flashes 4 times. I've read the manual but not sure where to go from here. Any advice is greatly appreciated .

January 19, 2009 11:17 AM

Thank you for your excellent postings.

 need your referral to i.c. supplier                                             for   Sony KP-57WS510

   convergence I.C.'s       STK 392 - 150        and    STK 392 - 180

appreciate your comments about low quality parts on the market , and do not want to make that mistake. ......   especially since I have 25 years experience in the semiconductor industry.

also,   I should replace the pico fuses , since I will have the set apart

  Do you have a supplier source for these ?

Thanks for all your help - 

May 19, 2010 10:37 AM

home fusing and breakers cannot be compared with fusing inside electronic equipment, there is a whole other dynamic going on. In a television the loading of the circuit is engineered, in a home the loading is random, so blowing of a fuse or circuit breaker in a home is simply an overloaded circuit. But in a television or other electric device the loading is calculated and known so if the loading is in excess of the fuse something has failed inside the device. That was my point. People understand fusing in a house and they try to apply that knowledge on fusing inside electronic equipment. And that can be dangerous.

View unverified member's comment - posted by ravnil

August 28, 2012 9:15 AM

There is no fuse in an oil furnace as far as I'm aware so it's unlikely to have any of the problems that have been mentioned. I think there are some fuses in electric and gas furnaces though so maybe it is more relevant to these types of systems. It should be noted that oil furnaces need regular maintenance so that they stay in good working order. Otherwise, you may need the oil furnace repair service people to come and start fixing it.

View unverified member's comment - posted by manmohan

Discussion:    Add a Comment | Back to Top | Comments 1-6 of 6 | Latest Comment

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