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Samsung LN46B550K1FXZA LCD (03/09) P/S Inverter Question.    
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Joined: 24 May 2014
Posts: 1
Location: statesboro

PostPosted: Sat May 24, 2014 5:15 pm    Post subject: Samsung LN46B550K1FXZA LCD (03/09) P/S Inverter Question. Reply with quote

Hi Everyone, thanks for the great forum. First time here but I wish I would have found ya'll long ago. I'm not a "TV repairman" by trade but every one of the 5 sets in my house came from either the side of the road or craigslist bought cheaply bc they didn't work. I've been repairing electronics as an amateur since I was a kid. (a smaller kid, I'll always be a kid, I'm just 46 now).

Enough rambling. This C/L acquired Samsung clicks a cpl times, the CCFL fires a for a second each click and then it gives up and that's all it does. Caps are Good, Inverters are good, What I have is 3 of the four large heat sinks on the board are hot (67 vac) when plugged in. 67-68 VAC as measured from the chassis to the heat sinks) Taking them to chassis pops the main fuse by the a/c plug. Obviously "something" has shorted, I've looked and checked? Anybody seen this? Ideas? Please don't tell me to "replace the board..." If that's how you roll then roll on brother.

I'm from the old school of component level repair - if and when possible. It is all but a forgotten time. I have changed the top Y-buffer board driver chip on some Samsung plasmas... first one took 4 chips, (destroyed3), 3/4 big bottle of Tylenol, 1/2 same size bottle of zane x, Several bottles of Absolute, and about a month or so of my time that I will never get back. But that set is still going strong 4 years later. Determination is the main ingredient to success. (for those unaware those buffer board chips are about 1" square with idk 90 legs a side or so, they make hairs look large) I am not trumpeting my accomplishments I just want to tell anyone that doubts themselves with patients and education and people like the ones right here on this forum, you can fix it, don't give up. If that just doesn't work out they do make great targets if your a shooter. Thanks for the great platform and people.

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Joined: 28 Dec 2006
Posts: 2879
Location: Overland Park, KS

PostPosted: Tue May 27, 2014 8:42 am    Post subject: Reply with quote

I'm not familiar with your particular TV, but...

Your description of 67VAC sounds like one of the main diodes in the primary side of the power supply's bridge rectifier has shorted and is no longer rectifying the AC voltage, but is instead passing it directly through.

If this is happening in the secondary stage of your power supply, it could be perfectly normal... in which case, I probably shouldn't be answering.

Joined: 21 Jan 2009
Posts: 2395
Location: Far, Far Away

PostPosted: Tue May 27, 2014 1:19 pm    Post subject: Reply with quote

Heat sinks in today's sets are usually NOT at COLD ground.

From your sets service manual's troubleshooting tree:

4-1-2. No Power
The LEDs on the front panel do not work when connecting the power cord.
The SMPS relay does not work when connecting the power cord.
The units appears to be dead.
The IP relay or the LEDs on the front panel does not work when connecting the power cord if the cables are
improperly connected or the Main Board or SMPS is not functioning. In this case, check the following:
Check the internal cable connection status inside the unit.
Check the fuses of each part.
Check the output voltage of SMPS.
Replace the Main Board.
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