Author Topic: LG 47LH40-UA  (Read 8679 times)

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Offline CarbenZone

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LG 47LH40-UA
« on: December 01, 2014, 03:10:23 am »
I recently had my 5 year old 47" LG encounter an issue. The right side CCFLs cut out. The TV still powers on for about 8-10 seconds before cutting back out. I opened the TV to inspect the boards and troubleshoot the issue. I located what seems to be the only issue. On the Power Supply board, there is a disc capacitor on the output side of the inverter that has obviously failed. The boards PCB number is: EAX56851901/31. Model number: LGP47-09LF. Revision 1.4. I am having a very difficult time finding a replacement capacitor for the board as it is a high voltage cap and no one sells them open to the public. The cap that has failed is rated at 54J, 6KV. I'm a little new to the repairing of electronics and I am not sure exactly what I would need or what the ?f rating is for it. If anyone could help me find the correct cap that would be a HUGE help!
 

Offline tautech

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Re: LG 47LH40-UA
« Reply #1 on: December 01, 2014, 03:41:35 am »
Welcome to the forum.
Put "54J, 6KV" in Google for results.
You might have to buy HV caps 5 or 10 at a time from some of the ebay or Aliexpress sellers.
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Offline CarbenZone

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Re: LG 47LH40-UA
« Reply #2 on: December 01, 2014, 03:48:24 am »
Thank you for the greeting. and oh... wow... and to think i was having a very hard time finding them... I even called local LG Cert repair centers in my area and they were going to charge me $80 to look at the thing and I'm sitting here like I already know whats wrong, the darn cap failed! But unfortunately its against their policy to sell parts to the public. Also what is the farad rating for the cap? can you tell from the information given?
« Last Edit: December 01, 2014, 03:52:08 am by CarbenZone »
 

Offline tautech

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Re: LG 47LH40-UA
« Reply #3 on: December 01, 2014, 04:24:40 am »
54 pF. J will be code for the tolerance. (+ or - some %)
Google capacitor tolerance codes.
You could pull one of the others and measure to confirm/be sure.
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Offline CarbenZone

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Re: LG 47LH40-UA
« Reply #4 on: December 01, 2014, 04:29:26 am »
except for the fact that LG only used that cap once on the power board. The left side CCFL's have a 22J 6kv cap on them.
 

Offline Richard Head

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Re: LG 47LH40-UA
« Reply #5 on: December 01, 2014, 07:33:55 am »
That's a special class-Y capacitor that bridges the isolation barrier. It's a safety critical component so you should replace it with a similar type of cap.
I'm sure you can get them from RS and Farnell.
I wonder what caused that cap to fail as it rated to at least 2kV I think?
 

Offline Richard Head

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Re: LG 47LH40-UA
« Reply #6 on: December 01, 2014, 07:35:11 am »
That's a special class-Y capacitor that bridges the isolation barrier. It's a safety critical component so you should replace it with a similar type of cap.
I'm sure you can get them from RS and Farnell.
I wonder what caused that cap to fail as it rated to at least 2kV I think?
 

Offline tom66

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Re: LG 47LH40-UA
« Reply #7 on: December 01, 2014, 10:21:25 am »
That's a special class-Y capacitor that bridges the isolation barrier. It's a safety critical component so you should replace it with a similar type of cap.
I'm sure you can get them from RS and Farnell.
I wonder what caused that cap to fail as it rated to at least 2kV I think?

It's not a class Y capacitor. It's a ballast capacitor for the CCFLs, it's used as part of the resonant tank (along with the transformer and negative impedance of the bulb) to start the bulbs.

When the set turns on, the bulbs will see 2-3x start voltage compared to operation voltage (around 600-1500V)
 

Offline Richard Head

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Re: LG 47LH40-UA
« Reply #8 on: December 01, 2014, 12:20:49 pm »
Tom66

Apologies, I see you are quite correct. I looks similar to the classic Y class caps in switchmode PSU's etc. It looks like they use two in series, probably for voltage rating.
They are likely polypropylene dielectric for low dielectric loss.
Dick
 

Offline Rasz

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Re: LG 47LH40-UA
« Reply #9 on: December 01, 2014, 06:29:30 pm »
LG Cert repair centers in my area and they were going to charge me $80 to look at the thing and I'm sitting here like I already know whats wrong, the darn cap failed! But unfortunately its against their policy to sell parts to the public.

places like that "repair" on the board level, that means they replace boards one by one until product starts working :) basically trained monkeys
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Offline CarbenZone

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Re: LG 47LH40-UA
« Reply #10 on: December 01, 2014, 08:12:03 pm »
Actually suprising enough, one of the locations actually tries to repair at the component level first before board level. And I'm not about to pay $80 to have them look at the board and say, "Oh yeah, that cap is bad," and then charge me another $50 for "parts and labor"
 

Offline denelec

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Re: LG 47LH40-UA
« Reply #11 on: December 01, 2014, 11:38:13 pm »
That's why I will never buy any LG stuff.  Parts are not available.  :--



 

Offline CarbenZone

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Re: LG 47LH40-UA
« Reply #12 on: December 02, 2014, 12:00:35 am »
Here's a video of what was happening when the TV died. Displayed on an LED TV. Our cable provider is not great and we think something is faulty with the digital receiver. No other receivers in the house do this. The TV will change the brightness or intensity of the CCFLs to make a more even color/brightness through changing scenes. I think the rapid on and off of the signal caused voltage spikes as the system is trying to change the brightness to compensate for the rapid "scene changes".
http://youtu.be/J4JAVAPitik
 

Offline CarbenZone

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Re: LG 47LH40-UA
« Reply #13 on: December 02, 2014, 12:08:55 am »
Also, all the blue box says that keeps coming in and out from the right side is:

"Sorry, there is currently no TV signal detected for this
channel. The channel may be temperarily off air.
Please try again later. If the problem continues,
please contact (Insert cruddy provider here) at (xxx)
xxx-xxxx. Reference x.1.1.1 when calling.
Alternatively, you can press the GUIDE button on your
remote control to watch programs on other channels."
« Last Edit: December 02, 2014, 12:11:38 am by CarbenZone »
 


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