Samsung Plasma PN64F5500

[burgerga]

Hi,

I'm trying to repair a Samsung Plasma (PN64F5500). The tv wouldn't turn on and I was able to determine that the two FETs that drive the Vs and Va transformers were bad. After replacing those, the set still will not turn on.

When attaching the power cord, Vs and Va jump to around 220V and 55V but immediately start dropping as their capacitors discharge. The LED on the front shows solid red. When I press the power button the LED blinks slowly 5 times then goes out and the button has no more effect.

The main board has a slowly blinking green LED and the heatsink of the CPU does get warm so something at least is functioning there.

On connector CN801 which goes to the main board I see the following voltages:
STBY: 5.26V
PS_ON: 0.14V
Vs_CON: 0V
Vs_ON: 0V
D15V: 14.9V
D5.3V: 5.26V

I'm not sure where to go from here. Any ideas what to look at next?

EDIT: Here are some pictures

TV info:


Y Sustain & Buffer:


Power Supply:


X Sustain & Main Board:


Power Supply Info:


The two replaced FETs:

[sordids999]

Re: Samsung Plasma PN64F5500

Posting pictures of the back of your tv showing the boards with clear pictures may help you more with fixing your problem

[burgerga]

Re: Samsung Plasma PN64F5500

Added some pictures to the post for ya sordids999.

[ReeceyBurger123]

Re: Samsung Plasma PN64F5500

Can I just ask quick did you add thermal paste to them new fets ? Also have you tried disconnecting the Ysus and Xsus ? If so does Vs and Vs stay up for longer ?

[burgerga]

Re: Samsung Plasma PN64F5500

I did add some Arctic Silver behind the two new MOSFETs.

With regards to unplugging the sus boards. When the boards are attached Vs and Va discharge at about 1-2 V/s. Unplugging the power output connector, Vs drops close to 10V/s and Va is still the same 1-2V/s.

[martino]

Re: Samsung Plasma PN64F5500

http://www.ebay.com/itm/Samsung-BN44...YAAOSwKsRWFxLc

[Nick's Tvs]

Re: Samsung Plasma PN64F5500

Burgerga,

First thing first, lets isolate your power supply and make sure it is ok. with all boards disconnected jump PS-ON to ground and VS-ON to 5volt line. Check VS and VA.
If same issue, I would suggest flipping your board upside down, and looking out for cracked solder joints. This SMPS is infamous for having one of the blue ceramic capacitors to have the smallest cracked joint I have ever seen every time, so really look for it. This capacitor is always the same one, and unfortunately off the top of my head I forget its location, but I believe its the one in between the middle heat sink and that transformer next to those 2 other blue box looking caps. I think its a combo of the transformer and the heat sink dissipating heat to that cap and causing the joint to go out prematurely.

[burgerga]

Re: Samsung Plasma PN64F5500

Thanks for the link Martino, I had no idea such packages exist! That might be my last resort before buying a new board if I can't nail down what component is bad.

Nick, thanks for the info! I was shorting PS-ON to ground but wasn't sure what to do with any other signals. I had looked for cracked solder joints (and touched some up for good measure) but only on the TO-220 and such components. It looks like this board has a lot more components riveted (is that the word?) than I've seen in the videos online, Samsung must be trying to fix some of these thermal issues. I'll jump right on these suggestions as soon as I'm home!

[burgerga]

Re: Samsung Plasma PN64F5500

Well, good news and bad news.... With your helpful advice on how to actually turn the power supply on, it looks like replacing the fets did the trick! I see a steady Vs and Va with PS_ON shorted to ground and VS_ON shorted to 5V3. I saw a bit of a ring at the caps you were talking about (see below) and touched them up just in case.

Unfortunately that means something other than the power supply is bad... Main board? Is there just some reset procedure that needs to be done?

[burgerga]

Re: Samsung Plasma PN64F5500

So this is weird. When I first posted this thread, when everything was plugged in it seemed that PS_ON was getting triggered, but VS_ON was not (see OP). The red light would be solid when plugging into power, then a click was heard and the light would flash 5 times when pressing the power button.

Now when I plug in to power I get 5 double-blinks and the power button is completely non-responsive. PS_ON sits at 5V3 and VS_ON sits at 0V.

The weird thing is that I didn't even do much. I solder bridged the pins when the SMPS was separate to test it, but I removed those and tested for shorts. The only other thing I did was touch up the solder joints of the suggested caps.

Do I just have a bad main board now? I figure there isn't much that can be done to diagnose and repair those right?

[sordids999]

Re: Samsung Plasma PN64F5500

Do I just have a bad main board now? I figure there isn't much that can be done to diagnose and repair those right?

You could try and see if you get test patterns off the control board to see if the main board is faulty

[burgerga]

Re: Samsung Plasma PN64F5500

How would I go about testing that?

Also I don't think that will result in anything. It doesn't seem like the main board is booting up at all right now. No PS_ON and the green indicator LED isn't flashing like before.

[mmartell]

Re: Samsung Plasma PN64F5500

The test patterns are generated on the control board and in fact the main board is disconnect for this test so it could tell you lots. You have to short two pins on the control board. Post a closeup of the board and someone will point it out.