How Do You Test A Metallized 400V 105K Polyester Film Capacitor?

[70JUDGE]

I have a Trutech PLV16260 LCD TV I have been trying to fix.It is over in the TV forum.I noticed a buzzing noise coming from the power supply.I traced it to a metallized polyester film capacitor marked 400V 105K.Is there any way of testing this?Are they supose to buzz?Thank You very much!

Tyler

[stj]

Re: How Do You Test A Metallized 400V 105K Polyester Film Capacitor?

they dont buz - post a foto of the top of it.

[70JUDGE]

Re: How Do You Test A Metallized 400V 105K Polyester Film Capacitor?

Here is what mine looks like.Thank You very much!
Tyler

http://cgi.ebay.com/10-Metallized-Po...item335799ac64

[Krankshaft]

Re: How Do You Test A Metallized 400V 105K Polyester Film Capacitor?

One of the inverter transformers, the main power supply transformer, or an inductor is more likely you need high frequency for something to buzz.

[70JUDGE]

Re: How Do You Test A Metallized 400V 105K Polyester Film Capacitor?

How can you tell if they are bad?Any way of testing them?I have been trying to fix my TV,but instead of going forward,I'm going backwards.
I replaced the capacitors that were bad,and the TV was working,then it would only stay on for a few seconds,so I started replacing capacitors that looked good.It seemed like the more capacitors I replaced,the less time the TV would stay on.The last capacitor I replaced,was the main 450V 150UF for the second time,and now the standy light goes out when the power button is pressed,but the TV won't turn on at all.Why I replaced the main capacitor again was bacuase it seemed like the faster I turned the TV back on again after the TV turned off by itself,the longer it would stay on.
While it was working,I could hear a buzzing noise,and I thought it was coming from the film capacitor.
I was told that I needed low ESR capacitors in the power supply for it to work right,or at all.That could be the reason why the TV was turning off by itself.Why it won't turn back on after replacing the main 450V 150UF capacitor,I don't know.Bad capacitor?It was the same brand,and series as the first one I replaced,but not the same brand as the original bad one.I checked both replaced new ones on as ESR meter,and they both check alright.Low capacitance?Thank You very much!

Tyler

[stj]

Re: How Do You Test A Metallized 400V 105K Polyester Film Capacitor?

well the foto isnt a safety-rated type.

the caps you replaced, what type old ones - what type new ones?
you may have put general use crap inplace of low-impedance parts.

[70JUDGE]

Re: How Do You Test A Metallized 400V 105K Polyester Film Capacitor?

The TV had low ESR KT brand to start with that went bad,so I replaced them with the following brands,and series.Rubycon MCZ,Rubycon YXA,Panasonic ED,Hitano EHR,Jamicon TR.So you really needed low ESR capacitors for the power supply to work right/at all,or just to make it last longer?Thank You very much!

Tyler

[stj]

Re: How Do You Test A Metallized 400V 105K Polyester Film Capacitor?

well YXA isnt low-esr, not sure about the others.
you do need low esr on psu outputs.

[1supertech]

Re: How Do You Test A Metallized 400V 105K Polyester Film Capacitor?

[QUOTE=70JUDGE;124375]I have a Trutech PLV16260 LCD TV I have been trying to fix.It is over in the TV forum.I noticed a buzzing noise coming from the power supply.I traced it to a metallized polyester film capacitor marked 400V 105K.Is there any way of testing this?Are they supose to buzz?Thank You very much!


Tyler[/QUOTE

Can a metallized polyester film capacitor be checked with a esr meter?
just for future Knowledge.

[Longbow]

Re: How Do You Test A Metallized 400V 105K Polyester Film Capacitor?

The short answer to your question is yes, you can test a mpf capacitor. Of interest would be the schematic of your power supply, btw. I think you would be better served by having a look at what should be happening, instead of just blasting parts. More specifically, an ESR meter would probably not tell you much since the value is 1 uf. The quickest test is to replace the cap. A real test has to put working voltage on the cap, in this case near 400v. A capacitance meter (many multimeters have them built-in) will tell you if it is 1 uf, and a 400v. power supply with current limiting will tell you if the part is leaking. That is the actual "test".

[1supertech]

Re: How Do You Test A Metallized 400V 105K Polyester Film Capacitor?

Thanks longbow

[tom66]

Re: How Do You Test A Metallized 400V 105K Polyester Film Capacitor?

Pulled a failed poly capacitor from a Yamaha amp, the amp would not power up.

Rated 22nF, measured... 6.5nF.

The failure mode is reduced capacitance.

And that's the only time I have used the capacitance range on my meter to diagnose an actual problem.