Hi guys!
First of all I want to say that the TV has been fixed already. I've seen a few threads here where the OP never gets back and I find it rather frustrating because you never know if the suggestions made by other members where useful or not. Here I want to explain step by step how I fixed the TV as a thanks to the forum and all the useful tips I read.
So let's get into it!
The TV is a Samsung LN32B450C4. It's assembled in Argentina and was widely available when it was being produced so there are still many around.
The problem originated when, being in stand by mode, I tried to turn it on. At that moment I heard a sparkly sound and it was gone.
I tested both fuses (FS801S and FM802S) and found that the second one was open.
I removed it and tested as indicated in the following image and discovered that something was causing a short.
After testing diodes, caps, transistors, etc I found that the STR-W6252 was causing shorted between pin#1 and pin#3 as you can see in the next image.
Those two pins correspond to the source and drain of an internal MOSFET so that part had to be replaced.
Up until then I thought (hoped) that the STR-W6252 was the only thing burned but then I read a few threads here were they talked about some MOSFETs in the inverter part of the PSU so I decided to test them and yep... they were gone.
I tested them (QI820 and QI821) by measuring resistance and found that they were extremely low (0,5 Ohm)
After checking the surrounding resistors and diodes I was pretty confident that I was done searching for burned components so I started searching for replacements.
Luckily for me I was able to get locally the STR-W6252. The MOSFETs on the other hand (F5N50UT) where nowhere to be found. As a replacement I picked up a couple of IRF830 that are rated 4.5A-500V and were also TO-220 but there was a little problem.
You see, the original TO-220 transistors were mounted on the same heatsink but since they were ALL PLASTIC there was no problem. On the other hand, the ones I bought have a metal back plate that is connected to the DRAIN. One quick glance at the schematic and you can see the beautiful problem that it was.
In order to solve this I had to use an insulator (it's called mica in spanish but I don't know the name in english) both for the TO-220 and the screw. It's the one in the picture.
And now they look like this
After soldering the new components I double checked for shorts. Since there were none I replaced de T3.15A ceramic fuse and plugged the whole thing to the AC line.
The stand-by led lighted up and then I turned the TV it on. It worked great
This was my mom's TV. As soon as she saw this one burned she rushed to buy a newer, bigger one...
Since I didn't have a TV in my place this has officially become my first TV
I leave you with a photo of the board
And the walk of shame :p
First of all I want to say that the TV has been fixed already. I've seen a few threads here where the OP never gets back and I find it rather frustrating because you never know if the suggestions made by other members where useful or not. Here I want to explain step by step how I fixed the TV as a thanks to the forum and all the useful tips I read.
So let's get into it!
The TV is a Samsung LN32B450C4. It's assembled in Argentina and was widely available when it was being produced so there are still many around.
The problem originated when, being in stand by mode, I tried to turn it on. At that moment I heard a sparkly sound and it was gone.
I tested both fuses (FS801S and FM802S) and found that the second one was open.
I removed it and tested as indicated in the following image and discovered that something was causing a short.
After testing diodes, caps, transistors, etc I found that the STR-W6252 was causing shorted between pin#1 and pin#3 as you can see in the next image.
Those two pins correspond to the source and drain of an internal MOSFET so that part had to be replaced.
Up until then I thought (hoped) that the STR-W6252 was the only thing burned but then I read a few threads here were they talked about some MOSFETs in the inverter part of the PSU so I decided to test them and yep... they were gone.
I tested them (QI820 and QI821) by measuring resistance and found that they were extremely low (0,5 Ohm)
After checking the surrounding resistors and diodes I was pretty confident that I was done searching for burned components so I started searching for replacements.
Luckily for me I was able to get locally the STR-W6252. The MOSFETs on the other hand (F5N50UT) where nowhere to be found. As a replacement I picked up a couple of IRF830 that are rated 4.5A-500V and were also TO-220 but there was a little problem.
You see, the original TO-220 transistors were mounted on the same heatsink but since they were ALL PLASTIC there was no problem. On the other hand, the ones I bought have a metal back plate that is connected to the DRAIN. One quick glance at the schematic and you can see the beautiful problem that it was.
In order to solve this I had to use an insulator (it's called mica in spanish but I don't know the name in english) both for the TO-220 and the screw. It's the one in the picture.
And now they look like this
After soldering the new components I double checked for shorts. Since there were none I replaced de T3.15A ceramic fuse and plugged the whole thing to the AC line.
The stand-by led lighted up and then I turned the TV it on. It worked great
This was my mom's TV. As soon as she saw this one burned she rushed to buy a newer, bigger one...
Since I didn't have a TV in my place this has officially become my first TV
I leave you with a photo of the board
And the walk of shame :p
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