Forcing on Power Supply with PS_ON

[tech2014]

I have a Samsung PN59D530A3F plasma tv that doesn't power up. All it does is clicks. I removed all connections except the main board and it still clicks. I don't see any VA or VS. I want to test the power supply outside the TV.

I jumped the ps_on pin to ground. The power supply clicks and stays on, but no voltages. I havent jumped a resistor to VS_ON to test VS since I want to test the main DC voltage. Am I doing this right?

I get 160V at main filter caps. Is there a PFC circuit on this power supply?

Part number is BN44-00445C.

[maxvalutech]

Re: Forcing on Power Supply with PS_ON

The main caps voltage is measured not to Gnd but by a probe on each leg of the cap and it should be between 350/400v. If the TV is from around 2011 on disconnecting y or z boards will cause shutdown anyway. Relay clicking indicates standby 5v is present (check that) and main board is sending turn on signal. Samsung put out monthly bulletin which is on the net and has useful info on servicing tips and there is a heap of stuff here on this subject. Circuits for PS almost nonexistent and I suggest search net for "troubleshooting smps circuits" or similar.

[maxvalutech]

Re: Forcing on Power Supply with PS_ON

That's Samsung Tech Talk and is downloadable .pdf

[Andrew F. Ali]

Re: Forcing on Power Supply with PS_ON

Send clear focused pics of the PSU board, connector and connector labels to the Main board. I may have a method to self-test the PSU board.

[tech2014]

Re: Forcing on Power Supply with PS_ON

I didn't get an VA or VS voltages when everything was connected, all I get is the 5v standby. I get ps_on, it goes to 3.2v then clicks and goes to .086V.

[tech2014]

Re: Forcing on Power Supply with PS_ON

I tested the VCC on the PFC IC. In the data sheet is says the VCC supply voltage is 24V. I am only getting 15.5V on the VCC pin.

[budm]

Re: Forcing on Power Supply with PS_ON

I tested the VCC on the PFC IC. In the data sheet is says the VCC supply voltage is 24V. I am only getting 15.5V on the VCC pin.

What is the PFC IC P/N? The 24VDC may be the max Voltage it can run on.

[tech2014]

Re: Forcing on Power Supply with PS_ON

Hi budm. I looked through the data sheet and it does say 24v is the max voltage for the VCC.

Here is a pic of the entire TV. I am 99% sure it is the p/s. I removed all boards and shorted PS_ON pin to GND to turn the power supply on. All I get is the standby voltage and nothing else. I also put a resistor on the VS_ON and input 4V to turn on the VA and VS. I still got no VA or VS. I only get 160V on the filter caps, I should be around 400V at full on mode, but it stays at 160V, or standby voltage.

Here is a pic of the TV boards.

[budm]

Re: Forcing on Power Supply with PS_ON

So it does not mean it needs 24VDC to run, so what is the P/N? 15VDC for VCC is about right but we need the spec sheet of the IC to verify. You can possibly have bad PFC diode.
Right now when GND the PS-ON (LO = ON for this power supply board) pin you should have close to 400VDC on the main filter cap, you need to get that PFC working first.

[tech2014]

Re: Forcing on Power Supply with PS_ON

Part number is R2A20118ASPW0, see data sheet below. I wish a schematic was available for the board so I can diagnose easier. Obviously the problem is on the primary side so I will focus on it when troubleshooting.

http://html.alldatasheet.com/html-pd...0118ASPW0.html

[budm]

Re: Forcing on Power Supply with PS_ON

15V VCC is fine, per spec. sheet minimum start Voltage is 10.5 (typ.), it will go into low Voltage shutdown if VCC is 9.3V or lower so Hysteresis Voltage is 1.2V.

Check PFC Diode DP809, 809 to see if they conduct both directions.

Pictures provided by shopjimmy.

[tech2014]

Re: Forcing on Power Supply with PS_ON

Diodes do conduct in both directions , any other ideas?

[budm]

Re: Forcing on Power Supply with PS_ON

Remove them and retest.

[tech2014]

Re: Forcing on Power Supply with PS_ON

ok, I thought you wanted me to test in circuit. So just take them out and they should show a voltage drop when measuring both directions forward and reverse bias? If so, they measure 0.5V only one way, OL other direction.

[budm]

Re: Forcing on Power Supply with PS_ON

ok, I thought you wanted me to test in circuit. So just take them out and they should show a voltage drop when measuring both directions forward and reverse bias? If so, they measure 0.5V only one way, OL other direction.

I did find a spare IN5408 diode in my shop and it measured in both directions, so I guess they are defective.

When the reading does not look right in the circuit then you have to it off the board, testing in circuit is just quick way to find out if it show bad reading.
If if it shows 'OL' in one direction and 0.5V on the other direction on both of the Diodes then they are good.
Good diode should show conduction one direction only (Meter in Diode mode with Positive to ANODE, Negative to CATHODE to forward Bias the Diode).

[tech2014]

Re: Forcing on Power Supply with PS_ON

I replaced both diodes and they both conduct in both directions in the circuit,measured fine out of circuit.

[jotto]

Re: Forcing on Power Supply with PS_ON

Part number is R2A20118ASPW0, see data sheet below. I wish a schematic was available for the board so I can diagnose easier. Obviously the problem is on the primary side so I will focus on it when troubleshooting.

http://html.alldatasheet.com/html-pd...0118ASPW0.html

I am not sure it is a primary problem. Primary should be very easy to troubleshoot. The ps is seeing a problem, you disconnected everything except the main. Leave the main board disconnected and turn on by ps on and ground.

If you are using the ground off the main cap on the primary side you will never see the correct secondary voltage, that is the ground for the primary side only. Use another ground point, that is on the secondary side.

Drawings are a thing of the past, most companies don't provide them.

[tech2014]

Re: Forcing on Power Supply with PS_ON

I am not sure it is a primary problem. Primary should be very easy to troubleshoot. The ps is seeing a problem, you disconnected everything except the main. Leave the main board disconnected and turn on by ps on and ground.

If you are using the ground off the main cap on the primary side you will never see the correct secondary voltage, that is the ground for the primary side only. Use another ground point, that is on the secondary side.

Drawings are a thing of the past, most companies don't provide them.

I am using the chassis ground for secondary and negative lead of filter cap on the primary side.

Does anyone know what area creates the PFC voltage? It would be so much easier with a schematic.

[budm]

Re: Forcing on Power Supply with PS_ON

So right now the PFC controller is getting the VCC to run, the PFC diodes are not shorted, it they are shorted then all you will get is 160VDC on the cap and no boosted Voltage.
So it is either bad PFC IC due to no drive signals to drive those two PFC Power MOSFET, r bad MOFETs which I doubt it very much to have both of them failed at the same time and most of the time they shorted out and will cause the main AC fuse to blow which is not you case. Or the Voltage at pin 3 BO (Brown Out) detection pin is not getting enough Voltage so it thing the incoming AC is too low so the PFC stays in the shutdown mode.
Check the Voltage on that pin 3 to see what you have, it is usually connected to high resistance resistors which often fail.
We need really good closed up pictures around that PFC IC.
BTW, the components with xxP are the components used in the PFC circuit, for example: dP809, icP801.

[tech2014]

Re: Forcing on Power Supply with PS_ON

The voltage is 4.5V on pin 3 of the PFC controller IC. Here are some pics of the PFC circuit.