Another Dead Samsung Plasma TV

[a1k3m1]

Hey dudes, my first post in this forums.
My question probably sounds quite newbie, But im just starting to learn electronics.

Ive got a Samsung Plasma TV (Model #: PS50C451B2D) which has done the common clicking Relay power board issues, So from some reading the issue is most likely some bad capacitors, as most have said, So I have gone around the Electrolytic Caps with a multimeter, and most of them look to be okay.

Except for one, There is a Cap which is rated at 3300uF @ 10Volts, and when I measure it in circuit with my Fluke 87V I get a reading of 3868uF.. Is this in spec of the Electrolytic Caps?. or could this be my problem?.. Im not quite up there with the working of Capacitors so im not sure, hopefully somebody could easily fill me in..

Thanks heaps!.

[cs.dk]

Welcome to the forums.
You can't measure dead caps with a multimeter.. It's not the capacity thats the problem, it's the ESR. Often the caps are bulged on top, thats a dead giveaway.

Caps are usually +/- 20% or so in rating.

[janoc]

You also shouldn't measure the caps in circuit using a multimeter - that won't give you accurate results.

You need an ESR meter instead - the cap may measure ok when measuring capacitance, but its ESR is so high that it doesn't work anymore for filtering the high ripple from the switching PSU. Bulging and leaking caps are an obvious giveaway, but not all bad caps will bulge and leak before the device stops working, so don't rely on that - an OK looking cap could still be bad.

Dave did a video on this:
http://www.eevblog.com/2012/10/06/eevblog-365-esr-meter-bad-cap-monitor-repair/

[mswhin63]

I have just finished repairing my brother Samsung 50" TV, The most obvious is capacitors, but in my case it was a dry solder joint on one of the PSU FETS.

The good thing about the Samsung, mostly the capacitors bulge so it should be easy to inspect. Mine were all OK no bulge so I moved onto the next stage and removed PSU connection to each board except the main logic board. This isolated all the external boards from the PSU.

Finally I removed the PSU to inspect the board before considering metering the circuit. As it is common for Caps and Dry Joints this is the main reason for inspection before metering. With a nice magnifying glass I was able to locate the culprit and re-soldered the joints. All working and sitting nicely in my lounge room. My brother gave it to me

I must admit servicing Plasma and LCD and LED TV's are so much easier than the old CRT screens. 

[tautech]

here is a Cap which is rated at 3300uF @ 10Volts, and when I measure it in circuit with my Fluke 87V I get a reading of 3868uF..

Likely to be another in paralell with it.
Only sure way is out of circuit.
Cut tracks to isolate it or remove it.

[a1k3m1]

thanks for the replies guys, I have looked over all the caps for bulges and bad solder joints, they all look from my eye to be okay.. ill remove them out of the board and see what happens as I think they could be linked with other caps, .

If im not successful I will just replace the lots of them anyways, as I have a collection of caps in the drawer. Would be cheaper than buying an ESR meter that I don't have 

Would it be any chance of a transistor or MOSFET going shotty you guys think?.. Would I test a MOSFET the same way I test a transistor?.

This TV has randomly switched on and off through the 4 Years ive owned it, But now it has finally finished itself off 

Anyways thanks again guys, ill play around with it more today and see if I can get it going!

[PaulAm]

You can build a usable ESR meter for less than $10,  probably less if you use your DMM as the indicator.  You don't need a lot of accuracy or precision for this job, just something to tell you a cap is bad.

[German_EE]

See https://www.youtube.com/user/norcal715/videos?sort=dd&view=0&flow=grid for lots of repair ideas.

[elliott]

Disconnect the sustain boards, if it stays powered up you have a short somewhere in one of them.