# loud POP vizio 42" lcd



## Jim Howard (Oct 26, 2010)

I just got a free 4 year old 42" vizio lcd tv that had popped for the old owner about 8 months ago, not real loud he said, but like a click. I took it apart and found the fuse blown...got new fuses and put one in, plugged in the power cord and immediately pop! saw smoke, and found a burn mark on the power board by a resister and large transformer. I have included an out of focus (sorry) pic. but wondering if anyone has an idea what the issue might be. note: I didn't know where to put this thread not finding a vizio section.
I think you can see the burn mark by the blue thingy.
Jim


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## lcaillo (May 2, 2006)

I moved it to the general DIY Repair and Maintenance forum. We don't have a Vizio forum but will consider it. 

I suggests posting the specifics if you want the highest probability of getting help. The precise model number and the location numbers of parts that are defective, tested, or that you have reported observations about are helpful.

I can't tell much from that photo. Do you have a service manual, or can you give a better image, maybe including more of the board?

It is a bad idea to replace fuses without doing some testing to find out why it blew in the first place. Chances are good that you did more damage but trying to start the power supply again with a short. A loud pop is likely a semiconductor or cap blowing. Look for a damaged cap or a semiconductor that is burned or blistered.


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## Jim Howard (Oct 26, 2010)

The brown mark is right next to a small resistor that looks like it has a small hole on top. The burn mark (I think) goes out from the side of the resistor. I see no other sign of damage or short or burn.

I am attaching 2 new pics of the power board.
Jim


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## Jim Howard (Oct 26, 2010)

pics too large..trying again


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## Jim Howard (Oct 26, 2010)

Question....I have a 42" dynex lcd tv in the basement that was given to me because the screen was cracked but everything else worked. Is there anyway I can find out if the lcd panel is compatible? or what models are compatible? they are both 42" lcd 2008 models


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## Jim Howard (Oct 26, 2010)

Nevermind, just found out they are different panels. Well, I can sell the boards from the dynex and maybe get some Vizio for this one. Do you think I need any boards other than the power board?


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## Jim Howard (Oct 26, 2010)

another question, how do i test transistors, two are inline with the resistor that blew. Also, I have no idea what the specs are for the resistor. Where can I find a schematic so I can tell what item is what?
thanks


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## lcaillo (May 2, 2006)

A good source of schematics is
http://elektrotanya.com

Most multimeters have a diode check mode. A transistor has two diode junctions in it. When testing a diode junction, placing the leads one way should result in a reading that is the forward bias voltage of the junction (usually around .6V) and placing the leads the other way will result in a much higher or infinity reading. If you get something closer to zero either way there is either a low impedance in the circuit in parallel or the diode/transistor is shorted.


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## Jim Howard (Oct 26, 2010)

ok, between moving and work, and feeling juist plain older, I have made some progress. I got a new powerboard. When it is plugged in, no noise (yaaah) but also no vizio emblem lights up either. Don't know if it did before I replaced the power board. I checked the voltage at the three different output pin locations. I get 5.01 volts where it says 5 volts, on 4 pins. The 12 volt and 24 volt markings and related pins have zero output? Is this any help to anyone out there?


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## Jim Howard (Oct 26, 2010)

progress...I discovered, using the troubleshooting chart for my tv, that checking the fuse (f2) I have 5 volts at one end and 0 volts at the other end. checking the fuse ( a surface mount type) that is is open. And, it is so small, I cannot read the printing on it, so I don't know what to replace it with. I wonder if I can use a standard type fuse wiring it to the ends of the surface mount one? I assume since that is the very first step in the troubleshooting process for no light, that it might just be the problem. And since the power board had a major poof....it caused that fuse to go as well. Any ideas?


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## lcaillo (May 2, 2006)

The the resistance from the load end of the fuse to ground. If it is low, you have a short somewhere that you have to track down before replacing the fuse. Yes, you can wire in a pico fuse or glass fuse with leads but be careful not to damage the board or create shorts. A 5 volt circuit probably would not need more than about a 1A fuse. I'd start with a 1/2A.


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## Jim Howard (Oct 26, 2010)

thanks....It did have a bad short before on thepower board, a blown ic with a hole in it, a blown fuse and resistor on the power board as well. could that have cause the little fuse to blow, or should I just assume more and double check to make sure. I am fairly new at trouble shooting electronics this way.


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## lcaillo (May 2, 2006)

It's hard to say without checking...


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## Jim Howard (Oct 26, 2010)

ok, I can't find surface mounted fuses locally and my soldering iron is the solder sucker type...hard to get to the little surface mount fuses. so, if I cant replace fuse right now, can I check any of the regulators on the board without it replaced? can I maybe jumper the fuse somehow? Or should I just bite the bullet and buy another soldering iron. I need to get something done with this thing cuz I can't afford to buy anything. so dissappointing.


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