magnovox 47' lcd tv problems..please help.

thumbsterApril 15, 2010

My model # 47mf437b/37 was working fine earlier today. now the red power button stays on. if you click it to turn on the tv then the picture comes up for a split second then the tv turns itself off. i called around to some tv places. wow expensive. i'm a laid off carpenter and if anyone could help me with this i would be grateful...i've tried unplugging it and letting it sit. then i looked at the on off button to make sure it wasn't stuck.....please help....

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maryland_irisman

Are you at all familiar how to test and replace components on a circuit board?

    Bookmark   April 15, 2010 at 8:21PM
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thumbster

have a little experience with circuit boards. do you think you know what it is? anyhelp would be much appreciated...thanks

    Bookmark   April 15, 2010 at 11:08PM
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jonnyp

More than likely it is capacitor failure. A problem that is wide spread, not just TVs. Lay the tv face down on a flat surface and open the back. Id the power supply , its where the power cord attaches. On this board you will see a series of cylindrical components. These usually have an x scribed in the top, if the top of the capacitor is bulging and the x has opened up or it is oozing brown crap, you have found your problem.There are couple of reasons 1) component of poor quality 2) component undersized, voltage rating to low.
There several resources on the web to guide you through this. I recently had a similar problem with a Samsung , one of the highest rated models 2 months out of warranty. I was surprised at the number of people having the same problem.The components and boards that compromise these sets are not necessarily the maker whose name is on the set. Google the problem and check You Tube.
Good luck , let us know how you make out. And by the way this a very cheap fix that techs are making a killing on.North of 2 bills for 1/2 hours work and maybe 10 bucks in parts

    Bookmark   April 16, 2010 at 9:43AM
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maryland_irisman

Undersized capacitors are a big problem as well as some of the printed circuits lifting from the board and then breaking, due to heat. Another cause for your problem may be poor solder connections. I've come across many problems like those you describe where the solder connections to various components were not complete or were marginal. Over time, from expansion and contraction from heat, the connection came apart. You can look for these with a magnifying glass. Another way is to take a plastic probe and slightly wiggle each component, pressing your "ON" switch each time. You'll know you hit the right part when it comes on and stays on. In my experience, if it's not a capacitor, it is a diode.

I think your problem is in the same circuit as the Infrared Receiver or, the video output circuit. If when you first turn the unit on and you get a picture for a split second and then the picture goes off, then I'd look at the diodes in the circuit board, in the direction of the circuit board, toward the video tuner. It would most likely be the very first diode after the IR receiver.

Here's a trick that is used on the bench to very quickly identify a bad component...Use a can of "Dust Off" used to blow out computer equipment for key boards and the like. Turn it upside down, aim the straw at a component and push on the spray button. This causes a liquid to come out and instantly freezes the component. This especially works well to find a defective transistor, voltage regulator or computer chip that is now in the tv's. The liquid does not conduct electricity and is non toxic. Spray each component and keep hitting you on button on the remote until the unit comes on and stays on a bit longer and you've found the defective part. Once the frost melts and the component heats up, the tv will likely turn off. But now you have found the problem child. As I said, if a capacitor hasn't failed, you'll find it to be a diode. I would check the solder joint for the diode before replacing the diode. If you look at the joint and it looks like a hole with the wire poked through, it's a bad joint. It should look like a solid bump.

If you see a suspect joint and decide to hit it, you have to be very careful not to use too much heat and you must touch the joint and go. You should us a heat sink on the wire side of the component or you will destroy it real quick. Keeping the soldering iron on the joint too long or too hot will destroy the component as well as lift the copper printed circuit from the board.

    Bookmark   April 16, 2010 at 10:53PM
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tim45z10

Sorry about topic change, but i am curious.
I had a CRT Magnavox that had the smart sound. The volume would not change during the show. Does your flatscreen have this feature?

    Bookmark   April 22, 2010 at 4:25PM
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