Samsung HPR5072- No Power- No Standby

[fixitjunkie]

Hello All,

My Samsung 50" Plasma experienced a lightning induced voltage surge resulting in no power and no standby light condition.

There is voltage going to the Power Supply board, but no AC voltage present at either test point Vs or Va.

From what I've read, there's a 50-50 chance between the Power Supply PCB or Main PCB.

There are some threads about unpluging ribbons and jumpering pins to determine if it's the main board but not sure if pertains to this model.

I have some experience working on electronics but not with TV's.

Any feedback would be greatly appreciated. Thanks.

[tvtimmy]

Re: Samsung HPR5072- No Power- No Standby

Take a look at these 3 capacitors, they look like they are bulging.

[fixitjunkie]

Re: Samsung HPR5072- No Power- No Standby

Which caps are you referring to? Attached is a photo of the Power Source PCB.
Should I just try a used one? Thanks.

[R_J]

Re: Samsung HPR5072- No Power- No Standby

These look bad (picture is not that clear)
Just so you know, Vs and Va are DC voltages NOT AC

[fixitjunkie]

Re: Samsung HPR5072- No Power- No Standby

Thanks RJ! I see the bulge on these caps compared to the others.
Rechecked for DC voltage at Vs and Va. No voltage present.
I'm going to order a used board and try it.

[R_J]

Re: Samsung HPR5072- No Power- No Standby

With those 3 caps bad it is unlikely you will have any Vs voltsge

[fixitjunkie]

Re: Samsung HPR5072- No Power- No Standby

This cap is on the Y-Main PCB.
So these caps explode due to the surge...an acute failure?
Do I need to address this failed cap before swapping the Main Power PCB and powering up?

[tvtimmy]

Re: Samsung HPR5072- No Power- No Standby

They mainly fail due to age, you must replace every bulging cap to start with. One bad cap can shut down a tv. The one on the ysus can give you a bad picture. The 3 on the power supply are the reason the tv wont turn on. Replace them first as the are cheap compared to a new board. NOTE: THE NAME OF THIS FORUM IS BADCAPS.

[fixitjunkie]

Re: Samsung HPR5072- No Power- No Standby

Got it...Thanks!! So a new Ysus board is $120. Out came the soldering pen.
Some of the characteristics are obvious but not sure about the tolerance and some of the other letters. Some cap manufacturers advertise low ESR. Does this matter or will any manufacturer suffice?

[tvtimmy]

Re: Samsung HPR5072- No Power- No Standby

Get the low esr caps.

[fixitjunkie]

Re: Samsung HPR5072- No Power- No Standby

I replaced three caps on the original power supply PCB and one on the Ysus PCB. Still no power or standby. Then, I swapped the original power supply board with a used one. IT'S FIXED! I'm still curious what failed on the original board. Maybe I should just accept victory and let it go. Thanks for the insight TVtimmy and RJ!! Will gladly be donating to the site.

[R_J]

Re: Samsung HPR5072- No Power- No Standby

The 3 bad caps were in the Vs circuit. If you have no STANDBY voltage, that is a different part of the board.
U101 is the standby ic, T101 is the standby transformer. Check for standby voltage on D108 cathode, it should be around 5Vdc. You can work on the power supply out of the tv but be careful as the primary side is connected to a/c line voltage.

[fixitjunkie]

Re: Samsung HPR5072- No Power- No Standby

So I can wire a 120VAC bench source to the board and check for 5VDC across
D108?

[fixitjunkie]

Re: Samsung HPR5072- No Power- No Standby

Rechecked the fuse again and supplied 120VAC to the board. No DC voltage
across D108.

[R_J]

Re: Samsung HPR5072- No Power- No Standby

You don't measure ACROSS the diode, you measure from ground to D108 cathode. Check the fuse F102, if it is open, ic101 is likely bad, (is it a, VIPer22A?)

[fixitjunkie]

Re: Samsung HPR5072- No Power- No Standby

Fuse checks good. Checked for DC voltage on both sides of D108 to ground (used negative side of several capacitors for a ground point). No voltage present. It is a VIPer22A.

[R_J]

Re: Samsung HPR5072- No Power- No Standby

Check the voltage across C101, you should have 160vdc across the cap. Also check RT201 thermistor, it is likely around 10~20Ω but should not be open.

[fixitjunkie]

Re: Samsung HPR5072- No Power- No Standby

Voltage across C101 - 165V
Resistance across RT201 - 18 ohms

[R_J]

Re: Samsung HPR5072- No Power- No Standby

The fault is likely U101, that circuit is fairly simple so there is not much that can go wrong. You could try replacing C104 & C170 and see if that helps. Check that R145 is not open and that ZD102 is not shorted.