EMI Interference From Samsung TV (UE55H6475)

[wasting]

Hi!

About 2 weeks ago my samsung tv (UE55H6475) started to interfere on the radio band around 410kHz and every 50kHz up to 2MHz.
At the start the tv did not interfere all the time, the problem seemed a bit random.

The last couple of days the interference is consistent, every time we start the tv the interference only comes when the power to the fluorescent lamp kicks in. It's a switched power supply rated at 1200v and 170mA. The tv is about 5 years old.



My guess is that one of the condensator in the EMI filter has gone bad. What do you guys think?

Thanks for any reply!

[SeanB]

Could be the earth connections are loose or dirty under the board, or the capacitors in the power supply are starting to fail.

[wasting]

Could be the earth connections are loose or dirty under the board, or the capacitors in the power supply are starting to fail.

Thanks for your answer!

I've checked the earth connection and it all seems fine to me. both visually and with a multimeter.

Can bad caps in the power supply (not the onces for the EMI filter) cause EMI interference?? Shouldn't these caps just "produce" a higher ripple on the dc voltage?

Cheers!

[SeanB]

Higher ripple will be radiated on the power supply lines, and 50kHz is about right for the switching frequency of the SMPS. Likely that it is only starting at 410kHz is that then the length of the wire is long enough to couple as an antenna. Cap change time, replacing the CapXon or Samwha with Nichicon ( not fake though) which you probably can get from Badcaps.net.

[tautech]

I'll second SeanB's diaognosis and reasoning.
I've seen PSU smothing caps values degrade to only a few uF's when they should be a 1000 or more and the circuit still work. 
Definatly where I would start. 

[wasting]

Ok! I will check all the caps! Thanks for your answers!

[T3sl4co1l]

Electrolytics are unlikely to cause EMI problems.

If the X1 (line-to-line) caps (pictured, blue boxes) are poor quality or your AC line is prone to transients, self-healing will reduce their capacitance and filtering will go to crap.  I don't know that I've heard of increasing EMI being a problem, but it's a possibility anyway.

Tim