Samsung PN63B550T2FXZA Power Supply Fuse Blows When Plugged In

[yompi]

So I have a 63 inch plasma with the model number in the title and the other day while watching TV I heard a few clicks and the TV shut off. I tried to turn it on but it wouldn't respond to the remote or the power button (red light flashes on TV normally when button is pressed on remote or TV).

I unplugged it and plugged it back in and it clicks a few times then the standby mode light stays on but once again it is unresponsive to any buttons.

So I opened it up and first thing I did was tested the fuses on the power supply. 2 of the 3 were good (marked green in the picture) and 1 was blown. I replaced the blown one (marked in red) and it blew as soon as I plugged it in.

So I tested the diode next to it (marked green) in circuit using the diode test mode and it looked good (open line way way and 0.556V the other way).

Then I tested the 3 FETs in circuit on the heat sink. 2 of them (marked yellow) read as shorts all ways. And one reads good (marked green).

Do you think it's just the 2 FETs that are bad? Or could it be more? Could it be that the transformers (marked with white question marks) knocked out these FETs?im just really confused as to where to go from here. I don't want to replace the FETs and fuse only to plug it in and have everything wiped out again.

Any input here would be appreciated.

Thanks
yompi

[dick_barton]

Re: Samsung PN63B550T2FXZA Power Supply Fuse Blows When Plugged In

Probably best to replace all 3 fets to be on the safe safe since the last one may have been stressed.

[Hamie]

Re: Samsung PN63B550T2FXZA Power Supply Fuse Blows When Plugged In

Replace FETS.
Solder in a lightbulb where the fuse is.
If the lightbulb lights up and stays lit you have another short.

If not check vs and va voltages are accurate and replace the fuse.

With the lightbulb in place you shouldn't do any damage to your replacment parts.

[ReeceyBurger123]

Re: Samsung PN63B550T2FXZA Power Supply Fuse Blows When Plugged In

Images of the whole Tv please ? Also agree with Db and Hamies points.

[yompi]

Re: Samsung PN63B550T2FXZA Power Supply Fuse Blows When Plugged In

Thanks for the prompt replies everyone. Really appreciate it.

When I get home I will see if I'm able to figure out which FETs I need to order but I may need some help choosing them.

Question about the light bulb method though: which side of the fuse is positive and which is negative? Also what kind of light bulb should I use? Fuse is an 8A 250V is that means anything.

I will also get post images of the whole TV once I get home.

[yompi]

Re: Samsung PN63B550T2FXZA Power Supply Fuse Blows When Plugged In

Below are images of the left, middle, right, and motherboard of the TV

[cliff_hootarski]

Re: Samsung PN63B550T2FXZA Power Supply Fuse Blows When Plugged In

Look at this thread, post 10.

https://www.badcaps.net/forum/showth...ht+bulb+method

[yompi]

Re: Samsung PN63B550T2FXZA Power Supply Fuse Blows When Plugged In

Update:

I replaced the 3 FETs with the exact replacement parts and used the lightbulb trick. When I plugged in the TV the light bulb didn't come on at all, which I assume is a good sign.

Then I put the fuse in but when I plugged the TV back I still wasn't able to turn the TV on. It had the same symptoms as before I replaced anything. It just makes weird clicking noises and is unresponsive when trying to turn it on. However, the fuse didn't blow when plugged in which is good right?

I tested the Va and Vs test points and they were extremely low (<3V). I'm not really sure where to go from here. Anyone have any ideas?

[yompi]

Re: Samsung PN63B550T2FXZA Power Supply Fuse Blows When Plugged In

Any ideas?

[yompi]

Re: Samsung PN63B550T2FXZA Power Supply Fuse Blows When Plugged In

Bump

[CapLeaker]

Re: Samsung PN63B550T2FXZA Power Supply Fuse Blows When Plugged In

The PSU won't turn on with that lightbulb trick in series.

[yompi]

Re: Samsung PN63B550T2FXZA Power Supply Fuse Blows When Plugged In

I got that from reading lots of other threads on here. I replaced the bulb with the proper 8A 250V ceramic fuse and it no longer blows when plugged in but the issue is the same as before.

[yompi]

Re: Samsung PN63B550T2FXZA Power Supply Fuse Blows When Plugged In

Does anyone know how I can test the 2 things marked with the white question mark in the original post photos?

[yompi]

Re: Samsung PN63B550T2FXZA Power Supply Fuse Blows When Plugged In

Ok so today I removed every diode from the circuit and tested them all with a multimeter in diode mode. The 4 diodes circled in red in the picture below seem faulty. They all show a voltage drop of less than 0.2V and I believe a good diode shows 0.4V-0.6V.

Question is should I replace them and hope those 4 diodes were the last of the problem or do you think there's a lot more wrong with this board?

It kinda makes sense why the 2 small diodes near the FETs I replaced went bad because they were somewhat connected. But I can't figure out why the bigger diodes on the far side of the board went bad.

Another question with the small diodes is do you think the rectangular IC next to the diodes could be bad? There's no physical sign of damage on the chip but is there any way to test it?

I'm very determined to get this set working again so any help or knowledge would be greatly appreciated.

Thanks
yompi

[CapLeaker]

Re: Samsung PN63B550T2FXZA Power Supply Fuse Blows When Plugged In

The voltage drop on a diode depends on what kind of diode it is. A low voltage drop would be correct for a Schottky diode. You would have to get the numbers of the diode and pull the datasheet and get the forward voltage drop and compare it with that what you measured.

Another thing: plug the PSU in and verify that you have standby voltage. Then you look for PSon (generated on the main board) at the PSU. If you don't have PSon, the TV stays dead.

[yompi]

Re: Samsung PN63B550T2FXZA Power Supply Fuse Blows When Plugged In

So the big ones are SR506. I'm measuring 0.16V and on the datasheet I found "maximum forward voltage" to be 0.67V.

The small ones are IN5819. I'm measuring 0.20V and on the datasheet I found "forward voltage" to be 0.60V 0.90V.

Is it safe to assume these are bad? If so, what're the chances these 4 little diodes are the end of the problem?

How can I verify I have a stanby voltage and PSon?

Thanks for your help