Help identify capacitor

[buz0340]

Hello,

I am trying to repair a lcd tv and I am pretty sure the power supply is shot. I have read in quite a few forums that the capacitors go bad. I have two questions, what are the specs for this capacitor. I think it is a 6200 pf capacitor. the picture below shows the capacitor.

Also, how could I test this capacitor along with the others on the board. All i have is a cheap multimeter.


p.s. Dont buy Akia.

[Al_The_Man]

You are pretty limited to checking with a Multimeter, but if you remove them, you can put the meter on the ohms range and check for shorts, if not shorted, you will see the meter ramp up as the cap charges, a rough indication is the time it takes before that ramp up stops and this is relative to the capacity.
If you reverse the leads you will see a -ve value and it will decay back to zero for the same time.
Again it is rough test for non capacity or shorts.
Also visually check for leakage.
Al.

[buz0340]

Thanks for the response Al,

When I put the ohm meter to the leads while on the board, it displays "1". When I connect it to a different smaller capacitor, the resistance rising up to ~680ohm. Is that what a working capacitor should do?

Also, am I correct on identifiy the size of the capacitor: a 6200 pf. This size seems to be very tough to find, so if you know of any sources that would be great.

Brian

[Al_The_Man]

If you mean one ohm, then either the cap is shorted or there is a low resistance or inductance across it, it is seldom usefull to measure in circuit, unless you know the exact circuitry.
I cannot see anything on the Cap that identifies its capacity.
You should be able to get at DigiKey or Newark.
Al.

[ViperTX]

It's an electrolytic...and I seriously doubt that it is 6200 pf...more likely 6200 mfd...not sure about the voltage rating....but most likely less then 100 vdc....measure its height and diameter.

Another way to tell if it is bad...the top has a vent that looks like a pie when it is sliced....if has been subjected to any overvoltage condition, etc. that vent will be open to some degree...and you may see some white looking like corrosion...like you see when dry cells go bad.

Paul

[buz0340]

Hello again,

There is no visible corrosion or leakage on the top. I included a picture of the cap below. The overall dimensions are roughly: length = 1.23", OD = 0.65".

How big (dimensions) is a 6200pf capacitor?

How should I approach replacing this capacitor? What specs should I research with?




Thank you for your help, its very much appreciated!

[Al_The_Man]

Originally Posted by buz0340 How big (dimensions) is a 6200pf capacitor?

About 3mm!

Originally Posted by buz0340 How should I approach replacing this capacitor? What specs should I research with?

It is quite possible the value is on the underside where you cannot see it?
If you don't know its function, it is risky to make a guess.
Al.

[buz0340]

I agree, I dont really want to be replacing parts I do not understand, but then again the tv is trash. If I can even get a power supply its gonna cost ~$180. So its worth a try to replace a couple capacitors.

I would like to switch gears here and test my power supply to make sure it is not working. I plug it into the wall and hooked up the multi meter to each terminal and only got one of the 5V outputs to display a voltage. It does make a high pitch squeel too, just an observation.

Was that an accurate test? Or do I need to put a load on the higher voltage outputs to actually get a reading?

Here is a picture of the power supply. The large capacitor in the center is the part I was previously referring to.



Thank you for your time,

Brian

[Al_The_Man]

In my experience in attempting to fix these switching supplies, it is most often either the solid state switching devices or toroidal transformers shorted over.
Al.

[buz0340]

Well, you have officially gone over my head. I don’t really have a response. This is what happened with the tv. First the tv wouldn’t turn on unless you unplugged/plugged it before turning it on. This occurrence became more frequent until the present, when it will not turn on at all. The red LED on the front of the tv does light up though. I can get a 5v reading off one output and the rest are zero.

It seems this is a common problem with akai customers, and many people say it is the capacitors burning out. I read one person who replaced the caps and the problem went away. I plan on removing the assumed bad capacitor from the board and test it with my multimeter. If it is bad, I will find a replacement. If it is good, I will search for a different capacitor that I believe is the problem. Basically until I go through them all.

I know this is probably not your process in troubleshooting a power supply, but it’s about the only thing within my capabilities I can attempt. Anymore of your comments, suggestion, or ideas would great.

Thankyou,

Brian

[Al_The_Man]

Most of my knowledge is in CRT TV but with an LCD it is most often the back light that goes, if this is so, the audio is usually still there, and so is the video, just that you cannot see it.
Small LCD's have around 1000v on the back light, I am not sure what large 46" TV's have?
There should be many N.G's out there that cover TV repair that should point you in the right direction, even a FTA site like ftatalk.com may have an expert.
Al.
Al.

[buz0340]

Hey Al,

Thank you for working with me. Ill end this thread soon.

I think that there might be a chance a couple of my capacitors might be "bulging". I linked two pictures below.

There are differences in the shape of the top from one to another. Some are almost dented inward, whereas some have an outward bulge (the 3 between the heat sinks). The second image does have a very small amount of tarnish near the center of it. Is this what a small leak might look like? How exaggerated does that "bulge" need to be for it to fail?

Thank you again,
Brian