Samsung UN58H5202 will not turn on. Help!

[sam steele]

My Samsung UN58H5202 just one day did not turn on anymore. No red standby light. Nothing.
So I googled and found some troubleshooting ideas and they said to check the power supply board. I Checked the pins for Standby Voltage and other pins next to it where the main board plugs into. All were reading 2.5V (except gnd which was as expected 0). I went to buy a replacement board and the parts store said the new power supply board may only work for a few days because faulty LED backlight strips on my unit may cause the power board to burn out again and that this is a common problem with this TV. Anyone ever heard of backlight strips doing this to a power board? TIA!!

[Andrew F. Ali]

Re: Samsung UN58H5202 will not turn on. Help!

With the TV unplugged from the 120Vac, disconnect the connector that from PSU to Main Bd. Plug the TV into the 120Vac and see if the backlights come on.

[budm]

Re: Samsung UN58H5202 will not turn on. Help!

Are you sure that the meter is OK and set properly?
The standby Voltage on this board is around 8V, and it will go up to 13V when PS-ON is present.

[nomoresonys]

Re: Samsung UN58H5202 will not turn on. Help!

https://www.youtube.com/watch?v=4v8DcqCNG4A Testing powersupply board, good place to start, always HEED HIGH VOLTAGE CAN BE DEADLY WARNINGS.

[nomoresonys]

Re: Samsung UN58H5202 will not turn on. Help!

https://www.youtube.com/watch?v=ocqnqmBxiqY more testing.

[nomoresonys]

Re: Samsung UN58H5202 will not turn on. Help!

https://www.youtube.com/watch?v=hT4rUkN7Xn0

[sam steele]

Re: Samsung UN58H5202 will not turn on. Help!

Hi Andrew, budm, nomoresonys,

I unplugged the tv then disconnected the connector from the psu to the main board then plugged the tv back in. No backlights came on.

I re tested the standby voltage and the other pins next to it and I get 1.4 or 1.5 volts only. I used two different meters that were set on DC.

I watched a couple of the videos nomoresonys suggested. Tested the main filler capacitor and it read 170 volts.

Fuse is good.

Not sure at this point whether to just buy a new PSU board or
PSU board and backlight led set as suggested by the guy at the parts store.

One parts store has this warning
ATTENTION!
The most common cause of power supply unit failure in Samsung UN58H5202 and UN58H5005 models is faulty LED backlight strip(s). Please consider replacing LED backlights in your TV set to prevent possible power supply failure in the future.

And Shop Jimmy warns:

PLEASE NOTE: The TV models that use this board have an above-average rate of LED strip failure. If your TV has sound but no picture (and a picture if visible when shining a flashlight on the screen) OR turns itself off on its own, there's a good chance the LEDs have failed. We carry replacement LED strips. The part number for the strips for this model is BN96-32771A/BN96-32772A.

Any thoughts? thx!

[jetadm123]

Re: Samsung UN58H5202 will not turn on. Help!

On the back of the power supply board there is a surface mount mosfet Q9101c that sometimes fails. Try checking it for short(s).

[nomoresonys]

Re: Samsung UN58H5202 will not turn on. Help!

"I watched a couple of the videos nomoresonys suggested. Tested the main filler capacitor and it read 170 volts" That looks about right for the standby voltage reading on the filter cap.

[nomoresonys]

Re: Samsung UN58H5202 will not turn on. Help!

https://www.youtube.com/watch?v=mUvclBfaMXg Testing powersupply by itself, unplug all other boards, he's using the ground pin for testing because he has board out of tv, you can just use the metal back of tv or other suitable ground for testing, IF you can't get a steady standby reading while testing with this methed, it's a powersupply board problem.

[sam steele]

Re: Samsung UN58H5202 will not turn on. Help!

On the back of the power supply board there is a surface mount mosfet Q9101c that sometimes fails. Try checking it for short(s).

Hi Jetadm123,

I un soldered the surface mount mosfet on the back of the board labeled Q9102c. Then tested after watching a few videos. Looks like it is not working.

How would I find the part number for this Mosfet? and where can I buy it in the Toronto GTA area?

There is another thread I found on this topic (see link below). It's suggesting it may be a good idea to cut the LED level from 90% to 50% after replacing the Mosfet. I assume this is done in the settings menu of the TV?

https://www.badcaps.net/forum/showthread.php?t=64699

I must have done something while testing things because now the fuse is NG and I will need to replace that as well.

Thanks! My nephew will be happy if I can get this TV to work for him and a good challenge for me (the novice).

[jetadm123]

Re: Samsung UN58H5202 will not turn on. Help!

Hi Jetadm123,

I un soldered the surface mount mosfet on the back of the board labeled Q9102c. Then tested after watching a few videos. Looks like it is not working.

How would I find the part number for this Mosfet? and where can I buy it in the Toronto GTA area?

There is another thread I found on this topic (see link below). It's suggesting it may be a good idea to cut the LED level from 90% to 50% after replacing the Mosfet. I assume this is done in the settings menu of the TV?

https://www.badcaps.net/forum/showthread.php?t=64699

I must have done something while testing things because now the fuse is NG and I will need to replace that as well.

Thanks! My nephew will be happy if I can get this TV to work for him and a good challenge for me (the novice).

Did you also check Q9101c? The part number of the mosfet is usually stamped on the mosfet itself. I'm not familiar with parts suppliers in Canada. There's always eBay....

[ejxxx]

Re: Samsung UN58H5202 will not turn on. Help!

hoping that there's no shorted diode connected to the mosfet

[neilc6]

Re: Samsung UN58H5202 will not turn on. Help!

Digikey ships to Canada for $8 Fedex next day with late cutoff time.

[sam steele]

Re: Samsung UN58H5202 will not turn on. Help!

Hi all,

I could not see the part number on the mosfet itself so after some searching online I found it could be BN81-04745A. Plus I need to check Q9101c and see if that is okay. Add a fuse thats needed and shipping costs, am I better off just buying a new board for $45.

However if I buy a new board and it burns out again due to bad LED strips, I am more $ into the repair.

I was thinking of maybe buying a new board and then turning down the LED level to 50% as suggested in another post. It suggesting that heat may be why the board is failing.
https://www.badcaps.net/forum/showthread.php?t=64699

Thoughts?

Thanks all!

[nomoresonys]

Re: Samsung UN58H5202 will not turn on. Help!

Hi all,

I could not see the part number on the mosfet itself so after some searching online I found it could be BN81-04745A. Plus I need to check Q9101c and see if that is okay. Add a fuse thats needed and shipping costs, am I better off just buying a new board for $45.

However if I buy a new board and it burns out again due to bad LED strips, I am more $ into the repair.

I was thinking of maybe buying a new board and then turning down the LED level to 50% as suggested in another post. It suggesting that heat may be why the board is failing.
https://www.badcaps.net/forum/showthread.php?t=64699

Thoughts?

Thanks all!

Turn it down as far as you are happy with picture, farther down it is the longer the lights will last.

[dcapper]

Re: Samsung UN58H5202 will not turn on. Help!

Not to hijack the thread but does anyone know the part number of q9101? Mine is burnt up.

[Pool Guy]

Re: Samsung UN58H5202 will not turn on. Help!

Not to hijack the thread but does anyone know the part number of q9101? Mine is burnt up.

Trying to figure out the same thing, I can see most of mine which definitely includes R380, likely ?0R380P possible first digit is an 3 but I'm just guessing on that. I did come across another website that linked the following, looks promising as it includes the part of the part # I'm sure of.
https://www.digikey.ca/products/en?k...EAUMA1CT-ND%20

[alfatv]

Re: Samsung UN58H5202 will not turn on. Help!

Did anybody buy 50R380 from Aliexpress? Or better to stay away?

[Storyteller12]

Re: Samsung UN58H5202 will not turn on. Help!

Definitely need to change led backlights. If that mosfet is bad then the backlights are bad. The lights are what took the mosfet out.