Samsung Plasma PN64F5500

[Jasin]

Hello, I currently have a PN64F5500 that stopped working last week. It was working fine one minute and then the screen went black with white text stating an update was in progress. Which isn't the normal update screen and I didn't initiate anything, never seen that before.

Anyways after about 20 minutes the tv was still completely black. Looked like it was turned off but there was no red light.

Tried turning it on, nothing. Unplugged, waited a while and plugged it back in. No red light, no power, no noise (my plasma always had an annoying buzzing noise).

It seems like it is the power board. I have a basic understanding of electronics and if I had a schematic I could test various components but not sure what all to test with just this board.

I edited the picture to show which few pieces I tested using the ground screw in the bottom right.






Tested the first fuse to make sure that wasn't blown. The 2nd fuse confuses me. It is 77 VDC on one end and -80 VDC on the other from the ground peg.

Across the 2 points is -162 VDC

The VA and VS both are at 0 VDC. Pretty sure I saw it at 10VDC one time, could have been from a CAP discharging.



Any help on what I could test next would be helpful. Thank you very much.

[Jasin]

Re: Samsung Plasma PN64F5500

Well I I just realized I should have been using AC across most.

So I updated the pic with new readings. Can't edit current post.

[Nick's Tvs]

Re: Samsung Plasma PN64F5500

your power supply more than likely is fine, it sounds like you may have a bad main board however. What voltages do you get out of the VS and VA lines going to the sustain boards? I assume you are not getting anything since the screen is black, but if you are please let us know what those numbers are. If nothing, disconnect both sustain boards from the power supply and check again. If still nothing let us know and I will let you know how to isolate the power supply to test it.

[Jasin]

Re: Samsung Plasma PN64F5500

your power supply more than likely is fine, it sounds like you may have a bad main board however. What voltages do you get out of the VS and VA lines going to the sustain boards? I assume you are not getting anything since the screen is black, but if you are please let us know what those numbers are. If nothing, disconnect both sustain boards from the power supply and check again. If still nothing let us know and I will let you know how to isolate the power supply to test it.

Hey Nick, Thanks for the quick reply. You are correct that the pins to the other boards are 0 both connected and not connected.

[Jasin]

Re: Samsung Plasma PN64F5500

Bump -

[Nick's Tvs]

Re: Samsung Plasma PN64F5500

Ok so lets go ahead and just rule out this power supply or confirm that it is the issue. Here is what you need to do.
Make sure all connectors are fully disconnected from the power supply. Then you will want to short PS-ON to ground and VS-ON to 5volt line with a 1k ohm resistor. Now you can plug the AC plug back in. What we have done is pretend that the main board is sending the turn on command to the power supply, which will trick it into activating even though it has nothing connected to it. Now take your VS and VA measurements. Make sure to do this in DC volts. Black lead to chassis ground, and red lead to the voltage line.
If you get proper voltage, then we know you more than likely have either a bad main or a bad logic. If you don't get any voltage or very low/oscillating voltages, then we know your power supply is faulty and we can trouble shoot it from there.
Let us know what you get.
Good luck

[Jasin]

Re: Samsung Plasma PN64F5500

Nick,

Thank you for the reply. I have to order a resistor since aren't any close electronic stores. But wanted to confirm something.

None of the 5.3 V pins (or any pins) on the power supply have any voltage. They are all 0. Does that matter? I can jump the pins when I get the part but just wanted to confirm that piece.

[Nick's Tvs]

Re: Samsung Plasma PN64F5500

If you don't even get standby voltage then your power supply is bad. It seems like you are getting voltages on the primary side however but none on secondary. Have you checked your transistors, and diodes for shorts? Have you tried flipping the board upside down to check for bad solder joints and or burn marks?
What is the part number of your power supply? BN44-*****

[Jasin]

Re: Samsung Plasma PN64F5500

Nick,

Sorry, I guess I should have marked the board better or stated the connection pins were all 0. I have attached a new picture with more readings.

I may have narrowed it down to the bottom right transformer. Not quite sure how to test it. The left 2 have 56 V on all 4 points. The bottom right only have 56 on the left 2 and 0 on the right 2. The 2 above them have plastic covering so I cannot test.

There are voltages on the 2 diodes next to it on the left and bottom but diode to the right is 0. I checked all transistors on the left and middle which are supplying power.

I did look at the back of the board the other day and could not see any bad joints.

Should I be testing most of this in AC or DC? Because if so all voltages on the left side of the board reading 55 VAC is 77 VDC and all the voltages on the right side of the board are reading -80 VAC. The fuse in the middle has the different voltages on each side.

The board part number is BN44-00618A

It's a big picture you can zoom in since I had to squeeze the readings in. Thanks a lot of your help.

[Nick's Tvs]

Re: Samsung Plasma PN64F5500

Check these QS802 QS804. Are those transistors shorted?

[dick_barton]

Re: Samsung Plasma PN64F5500

Have you given the readings found at the connectors as DC? Everything looks marked up as "AC" or "0". With your black lead on chassis and using the red lead, read the connector voltages with your meter set to DC.

[Jasin]

Re: Samsung Plasma PN64F5500

Check these QS802 QS804. Are those transistors shorted?

Nick,

That thermal paste was a pain to remove. Didn't want to just to bottom of board so I could confirm I had the right pins.

They seem fine. I did resistance tests between all 3 both ways none of them are 0 OHM. Most are 10M. Believe outside pins to the middle pin is only like 50 OHM. But I compared them to the other transistors around the board and seem to be the same.

I also powered the board and took voltage readings. all 3 pins are at different voltages.

[Jasin]

Re: Samsung Plasma PN64F5500

Have you given the readings found at the connectors as DC? Everything looks marked up as "AC" or "0". With your black lead on chassis and using the red lead, read the connector voltages with your meter set to DC.

I wasn't sure at which point I should be testing DC or AC. But the first post at the top was mostly all DC voltage checks.

Any pin listed 0 on the board I checked both AC and DC. Only different is if I do DC most of the 55 VAC is either 77 VDC or -80 VDC.

[Jasin]

Re: Samsung Plasma PN64F5500

So I want to go with I don't know how to correctly test them. I removed both the 802 and 804 and tested most of the board. All readings are the same that I have been getting so I want to assume they are bad.

Should I be looking at any other components or just try and replace these? Tried to look up the numbers on them but don't find anything.

F 1C17AA
F 1C15BA

[martino]

Re: Samsung Plasma PN64F5500

It was working fine one minute and then the screen went black with white text stating an update was in progress. .

Did the white letters on the screen stay on for those 20 minutes till you unplugged the unit?

[Jasin]

Re: Samsung Plasma PN64F5500

Did the white letters on the screen stay on for those 20 minutes till you unplugged the unit?

Nope, it was just a pure black screen. Didn't look like it was on at all.

[Jasin]

Re: Samsung Plasma PN64F5500

Check these QS802 QS804. Are those transistors shorted?

Ok so I replaced these. Pretty sure they were bad after comparing them to the new ones I ordered.

Still have same issue though. It came with some of the tiny components on the back of the board. but they are hard to test if there is an issue or not since i'd have to take some of them off to test. Any guidance on how to proceed from here?

[Nick's Tvs]

Re: Samsung Plasma PN64F5500

Unfortunately I do not have this board in front of me or a set to plug it into to check voltages. What I can tell you, is that you will want to check those surface mount components on the back side, and you will want to go ahead and check those transistors out of circuit as well. Outside pins being 50ohms is pretty bad, those transistors should be showing in the Mega homs or Overloard on your multimeter between most pins. It could be another component in parallel on the board however.

[Jasin]

Re: Samsung Plasma PN64F5500

I replaced all the surface mount components that came with the kit, no go. I guess I have no other choice buy to buy another power board.

Anyone recommend a good site?

[martino]

Re: Samsung Plasma PN64F5500

I replaced all the surface mount components that came with the kit, no go. I guess I have no other choice buy to buy another power board.

Anyone recommend a good site?

Did you replace UQ802? I bet you now lost you're 5volt standby,and have about 4.1 volt on ps-on,correct?
Hope you still have the old UC802,as the one in the kit don't work.
I have two boards here,one I just bought and one I'm trying to fix. If you need voltages etc,let me know.