Samsung PSU BN44-00504A PD23A0T_CPN broken

[shoe548]

I'm trying to diagnose what's up with the PSU on my Samsung TV, model BN44-00504A.

I can't see any visibly damaged capacitors, and I've had a go at resoldering some joints that looked dry, but no avail. I get no power to the backlight, and no readings from any of the pins except the A5V which is at around 4V (should be 5.3V).

I've attached some pictures, any help would be much appreciated.

[nomoresonys]

More pictures, one of every board and one of the whole back as to see how everything is connected, resoldering some bad looking joints is a great start, glad to see someone starting with this simple procedure.

[nomoresonys]

Simple test, unhook cable from powerboard to mainboard, plug power cord into powerboard, do backlights come on and stay on?

[shoe548]

Couple more pics attached. Already tried the backlight test and no it doesn't come on. Pretty sure it's something on the PSU based on that and the voltmeter readings being 0.

[nomoresonys]

What voltage does A5 have with that cable to mainboard unhooked?

[nomoresonys]

Whats the full model number of this unit.

[Diah]

from yours first post photo you did rework soldering on SMT parts close to STB IC but they are not clean.. look there are shorted points

[shoe548]

What voltage does A5 have with that cable to mainboard unhooked?

About 4V. None of the other pins have any voltage

[shoe548]

Whats the full model number of this unit.

I'll get back to you with the TV model later once I'm home, the full PSU number is in the title

[shoe548]

from yours first post photo you did rework soldering on SMT parts close to STB IC but they are not clean.. look there are shorted points

I'm not clear on which you're saying are shorted, I think the ones you are referring to were already like that and are connected anyway. I've checked with a multimeter and from what I can tell none are shorting that shouldn't be but it's a bit difficult without a schematic to determine, so anything specific you can see would be great

[nomoresonys]

If those pics were taken after solder reflow, some of those joints still look cracked.

[shoe548]

Whats the full model number of this unit.

UE22ES5400W

[shoe548]

If those pics were taken after solder reflow, some of those joints still look cracked.

I'll have another go at it tomorrow, unfortunately my soldering iron isn't the best.

[EazyBone]

Have you even tested the backlights with a tester?

[shoe548]

Have you even tested the backlights with a tester?

As in the voltage to the backlights from the PSU? Yes it's 0V

[vinceroger69]

As in the voltage to the backlights from the PSU? Yes it's 0V

This is a led tester a good tool to have if you repair tvs https://www.ebay.co.uk/itm/395174144...Bk9SR8Lcjv27Yw

[shoe548]

This is a led tester a good tool to have if you repair tvs https://www.ebay.co.uk/itm/395174144...Bk9SR8Lcjv27Yw

Thanks although I don't make a habit of repairing many! Also there's definitely no power to the main board either so I struggle to see how it could be an issue with the backlight?

[shoe548]

If those pics were taken after solder reflow, some of those joints still look cracked.

Again it seems difficult to get the joints to a good state but here's it after having another go. Still no avail, and the continuity of all the pints seems ok

[nomoresonys]

That looks better, was also referring to some others, from this last pic. make sure that one there by DM881 is not cracked.

[shoe548]

That looks better, was also referring to some others, from this last pic. make sure that one there by DM881 is not cracked.

Yeah it looks worse than it is in that pic, it's not cracked. I'm a bit at a loss really, looking like I may have to just get a whole new board