Samsung BN44-00175A Not Powering Up

[Barn01]

Hi all,

This is my first time posting and I'm hoping someone can help me out. I have a bn44-00175a power board from a Samsung 50" Plasma FP-T5084. The TV originally was clicking when powering and then shut down. My buddy opened the TV and changed the fuses (FE802 blown, and I'm not sure is FE801 was but he changed that as well). He also changed 4 bulging caps CB813, CB814, CX834, CX835. When he replaced one of the caps he lifted a trace and that's why I jumpered a little black wire on.

I have checked the FET's and they meter out ok (no shorts). I have reflowed the solder to all of the components that are tied to the heat sinks, plus all the larger electrolytic caps. I have tacked a 1.2k resistor from PS_ON to GND (this should turn the supply on but I hear no click from the relay). The stby V = 5V but there's no point jumping that to VS_ON until I get the board to turn on.

Am I right with what I've done so far and where do you think I should go next? I can't find a schematic for this PCB anywhere. I hope the pics are ok.

[flocko]

Re: Samsung BN44-00175A Not Powering Up

You do not need the resistor for Ps on, just put Ps on to ground, I would say if fuse FE802 was blown the FETs would be to ,and the SMD resistors and diodes on the bottom of the board

[Barn01]

Re: Samsung BN44-00175A Not Powering Up

You do not need the resistor for Ps on, just put Ps on to ground, I would say if fuse FE802 was blown the FETs would be to ,and the SMD resistors and diodes on the bottom of the board

You were right about PS_ON to GND. I thought the resistor would keep it safer but it doesn't drop the voltage enough (it was dropping it to 2.4V). So now I have the relay clicking on and off just as if it was in the TV stuck in failure mode.

The FET's all meter ok and match each other in fwd and rev bias. Do you think it's worth removing them all? Or does this now sound like a different problem?

Thanks

[ammarben]

Re: Samsung BN44-00175A Not Powering Up

read this
http://www.coppelltvrepair.com/p/516...ing-down-board

[flocko]

Re: Samsung BN44-00175A Not Powering Up

Can you see on the small daughter board by the connectors before you do PSon to ground do you have a green led showing and when the relay clicks what does the led do (you will see a screen print by the board indicating faults for the amount of flashes the green led flashes )

[Barn01]

Re: Samsung BN44-00175A Not Powering Up

I forgot to mention that I do have Va = 65V while the relay is cycling and once the relay stops the Va turns off.

[Barn01]

Re: Samsung BN44-00175A Not Powering Up

Can you see on the small daughter board by the connectors before you do PSon to ground do you have a green led showing and when the relay clicks what does the led do (you will see a screen print by the board indicating faults for the amount of flashes the green led flashes )

The green LED is on solid during the relay cycling and then it flashes twice, long pause, twice ... etc. I assume that means it's failing on error #2 and error #2 is 5.3V.

I checked and there is nothing on the 5.3V rail during or after the relay cycling.

[flocko]

Re: Samsung BN44-00175A Not Powering Up

This and the BN44-00222 are almost the same but there are no schematic for them , but as you have Va you should not have to much of a problem back tracking to were the 5.3v is going down as must be off the same transformer as Va, start checking on the last heat sink, you may find DC-DC buck converter/ diodes and regulators or caps could be faulty , but seeing if any of the other smaller voltages come up could help narrow it down

[Barn01]

Re: Samsung BN44-00175A Not Powering Up

This and the BN44-00222 are almost the same but there are no schematic for them , but as you have Va you should not have to much of a problem back tracking to were the 5.3v is going down as must be off the same transformer as Va, start checking on the last heat sink, you may find DC-DC buck converter/ diodes and regulators or caps could be faulty , but seeing if any of the other smaller voltages come up could help narrow it down

Standby = 5.2V
12V = 12.2V

Looks like it's just the 5.3V and according to the solder side chart it's a 7A rail so I assume I should be looking around the FET's of the big heat sink components. I'll keep poking around but if you have any ideas I'd love to hear them.

Thanks so far by the way, I'm not used to troubleshooting without schematics.

[flocko]

Re: Samsung BN44-00175A Not Powering Up

No as I said if you now say the 12v/ 63v are coming up, that would say to me that your problem lies on the secondary side,as you have some small voltages coming up the transformer is getting primary voltage, see if the others are coming up 15v/18v+8v? start buy checking any diodes +FETs on the last h/sink and any Z-diodes laying to the side of it

[Barn01]

Re: Samsung BN44-00175A Not Powering Up

No as I said if you now say the 12v/ 63v are coming up, that would say to me that your problem lies on the secondary side,as you have some small voltages coming up the transformer is getting primary voltage, see if the others are coming up 15v/18v+8v? start buy checking any diodes +FETs on the last h/sink and any Z-diodes laying to the side of it

Vg 15V = good
V amp 18V = good
Fan 8V = good

Still poking around.

[flocko]

Re: Samsung BN44-00175A Not Powering Up

Has it any five leg IC on that h/sink ?some board use DC-DC converters for 5.3v to save on space others will use FETs and Z diodes to regulate the output plus caps,work back from the 5.3v test point

[Barn01]

Re: Samsung BN44-00175A Not Powering Up

I think I'm good to go now.

I found a bad trace on the other side of the one that I fixed from when my buddy hack soldered in those caps. I fixed one side of it but I guess it was just intermittent when I checked after the fix. So I jumpered on to the +cap leg from both sides this time.

Powered it up and one click only with all voltages present. I jumped the VS_ON and got 206V so I'm good to go and I'll give it back to him.

Thank you so much for your help flocko!

[flocko]

Re: Samsung BN44-00175A Not Powering Up

No problem glad to help

[Hawk2112]

Re: Samsung BN44-00175A Not Powering Up

Reviving this thread for a question. Working on the same TV/power board.
It was working great but started clicking more and more before starting. Now it just clicks. It clicks multiple times then nothing.

The power board was my first thought. I have isolated the X sustain then the Y, then the rest one by one. Just kept clicking (riser board led flashing).

It clicks as long as the main board it attached. When the CN801 (main board connector) is pulled there is no click, not even the needed single one.

I pulled all connector except the AC and attached a jump wire between Vs_on and the 5.3V in CN807 as was shown above.

No click, no Va, Vg, or Vs, PS_ON has 4.9V

While clicking is cycling the Va=63V Vg=15V Vs=3V..

So my conclusion is SMPS is bad but before I order a replacement is there any other tests I should do? The main board causing the clicking is making me worry that its the main.

Thanks in advance.

[Hawk2112]

Re: Samsung BN44-00175A Not Powering Up

Reviving this thread for a question. Working on the same TV/power board.
It was working great but started clicking more and more before starting. Now it just clicks. It clicks multiple times then nothing.

The power board was my first thought. I have isolated the X sustain then the Y, then the rest one by one. Just kept clicking (riser board led flashing).

It clicks as long as the main board it attached. When the CN801 (main board connector) is pulled there is no click, not even the needed single one.

I pulled all connector except the AC and attached a jump wire between Vs_on and the 5.3V in CN807 as was shown above.

No click, no Va, Vg, or Vs, PS_ON has 4.9V

While clicking is cycling the Va=63V Vg=15V Vs=3V..

So my conclusion is SMPS is bad but before I order a replacement is there any other tests I should do? The main board causing the clicking is making me worry that its the main.

Thanks in advance.

Left out that I tested all caps and checked the board for cold solder joins etc..

[flocko]

Re: Samsung BN44-00175A Not Powering Up

Well you were almost right in what you tried , but first you must turn the power board on? to do this, remove all the connections apart from the mains in (see you got that right )then you need to find PSon on the connector that goes to the main board and ground that, and that will make the relay click and bring up all the small voltages 5.3/8v/12v/18/63v if you have these then you can with a 400-600ohm resistor jump VS on to the 5v stby to bring up the VS 206v .If you look back over the posts you will see we talk about the small daughter board with just mains power to the board (standby ) you should have a green LED on solid if the relay does not stay in (clicking ) the LED will flash a fault code giving you some idea of the fault (not always right though ). I hope this will be of help Flocko if you could tell us all were you are in the World it helps us with time lines to know when you will be on the forum

[Hawk2112]

Re: Samsung BN44-00175A Not Powering Up

Well you were almost right in what you tried , but first you must turn the power board on? to do this, remove all the connections apart from the mains in (see you got that right )then you need to find PSon on the connector that goes to the main board and ground that, and that will make the relay click and bring up all the small voltages 5.3/8v/12v/18/63v if you have these then you can with a 400-600ohm resistor jump VS on to the 5v stby to bring up the VS 206v .If you look back over the posts you will see we talk about the small daughter board with just mains power to the board (standby ) you should have a green LED on solid if the relay does not stay in (clicking ) the LED will flash a fault code giving you some idea of the fault (not always right though ). I hope this will be of help Flocko if you could tell us all were you are in the World it helps us with time lines to know when you will be on the forum

Thank you. will try this later today. Will update the profile stuff too. Canada (west coast).

To clarify the PSon to ground is only needed momentarily, until the relay turns on, correct? I will also check into the flash codes on the daughter board.

[flocko]

Re: Samsung BN44-00175A Not Powering Up

No the PS on to ground has to be maintained ,this is normally carried out by the main board when you hit the on button on the remote or side controls (as you noted PS on will be 5v when in Stby, but will go low when you try to turn on) check your small voltages and tell us what you find them to be

[Hawk2112]

Re: Samsung BN44-00175A Not Powering Up

Thanks,

Ok PS_ON grounded and the relays multi-click and then DB error flashes.

Flash error is 2 = 5.3V error and it is measuring 0V.

everything is 0V or falling to 0V (ie Va is slowly dropping as caps discharge)

The only correct voltage is the STBY at 5.2V

Hope this helps narrow the fault but I guess it also confirms the SMPS is the problem. Hoping I can find the component and fix rather than order a whole new supply.