Puffy Capacitor Overview how to test for bad caps on TV board &
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What is a Capacitor - DIY Testing a Capacitor - TV Help
This video is an overview about capacitors:
What is a capacitor
What does a capacitor do
How to test a capacitor
How to replace a capacitor
TV symptoms of a bad capacitor:
TV will not turn on immediately
TV takes a long time to turn on
TV turns on slowly
Power Supply Capacitor replacement
TV board repair kit
Component level TV Repair
TV will not turn on
So in this video today we are going to look at what a capacitor is, how it works, what it does, how to identify a bad cap and what happens when they do go bad, how to find a replacement and how to install it. So capacitors were originally known as condensers, so if you hear some of the old timers talking about a condenser, you know what it is. Basically they are used to store a charge. They are able to get rid of that charge very quickly, unlike a battery which is able to do it slowly, these can do it instantly.
In a power supply, generally you are going to see aluminum caps like this and possibly some of the polyester style like that. Generally they are going to be used for filtering out DC, because they allow AC to pass through. Or they are going to be used to help filter and to steady DC voltage going out to the main board or the T-con.
What happens when a capacitor goes bad?
Capacitors are affected by temperature and voltage, if they are rated for a certain voltage like this one is rated for 35 volts and you happen to expose it to a higher voltage, you may find that the cap starts to fail prematurely. Also, the temp can cause it to fail prematurely.
When they begin to fail, they may start to produce gas inside of them which will result in the tops becoming puffy. If its bad enough the top will burst open and allow the dielectric inside, the insulating layer to ooze out.
So often you will see a brown substance on top of the cap and sometimes on the board as well. Certain capacitors if they happen to fail spectacularly can actually blow the casing completely off and you will be left with something that looks like that on the board and you will see kind of like a paper outside and the little rubber stopper on the bottom and not much else.
In some TVs, some power supplies you will see that all the time and they will blow completely off the board.
So here we have a few examples of bad caps. As you can see the tops in these have blown open and some of the dielectric has oozed out from the inside. That happens just with the heat that gets generated inside the cap when it starts to short out and fail. This one here is close, the tops puffy, but it hasn't actually blown open yet. Again, this one will be bad and if you saw that on your board you would need to replace it. The common issues with bad caps tend to be the TV not powering on, the TV powering on, but taking multiple attempts. The multiple attempts will probably take more and more as time goes on and the cap starts to dry out even more.
Usually once the TV comes on its going to function normally, but again once you power it off and try and turn it back on, you are going to get those issues where it does not want to start up. The other kind of capacitor that you will see used on inverters or sometimes on power supplies that have high voltage sections on them going out to lamps are these little ceramic capacitors. These are often used for feedback from the lamps and if those go bad they generally don't go puffy like an aluminum caps, like these. What they are going to do is usually show a burn spot or they can crack and fracture. If those go bad, generally it acts like a bad lamp, the TV may come on briefly and then the backlights might shut off, the rest of the TV could stay on but your backlights are going to turn off.
If your backlights turn off, make sure that you check these caps. If you see any burn marks, or spots, anything like that. It is worth replacing them, make sure that you use the same voltage and capacitance. They are really picky on these little feedback circuits. If you do not put the right one in, it won't work.
This style here, the one with the polyester cap or teflon cap, generally these do not go puffy, but you will see burn marks and sometimes will see the one side will become kind of extended or bubble up more, just because there is more heat generated there. Again they are usually pretty easy to spot. Check for burn marks and cracks in the cap.
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