New power supply, but tv fails to power on.

[Marzog]

I have a Samsung LN32A540p2dzxa that recently decided to go blank and not power on at all. After some research, I discovered the samsung lawsuit stuff and long story short, I decided that I was suffering from a faulty power supply board.
I just got the new board today, (BN44-00208A), attached it, and had no luck.

All that happens when the tv is plugged in is I can hear a very faint ticking sound coming from the board. It appears to be coming from the the part labeled
"M32P5-PFC
SC-0830CM"

The standby light on the front of the tv doesn't come on whatsoever and the tv does not make the distinct powering on chime.

I refuse to give up on this thing completely, as I'm sure I'm just missing something right I front of me right now.

[Caleb]

Re: New power supply, but tv fails to power on.

Is the power supply new or ebay?
Do you have a multimeter?
Pictures of the open back of the tv and the individual boards help greatly in diagnosing trouble.
Since the power supply is ticking you may have a short on the standby supply on the main board, or you may have gotten a faulty power supply.

[Marzog]

Re: New power supply, but tv fails to power on.

I do indeed have a multimeter, but will need decent instruction on how to use it without frying something. Such as, if I'm gonna measure voltage, where do I turn the knob, etc.

The board is brand new out of the packaging. (At least it's supposed to be) And since the new board and the board that's been in the tv for 6 years make the same sound... I'm lead to believe there's a different problem. That or they somehow managed to suffer from the exact same thing.

What appears to be the source of the sound is the object in photo 4 with the yellow band. If you need better angles for the photos, let me know.

[Caleb]

Re: New power supply, but tv fails to power on.

It sounds likely that you have a fault on the main board or button board. Can you unplug the 2 harnesses going to the main (av) board and take a close up picture of the legend silkscreened near the connectors. You will likely need two 1k resistors to test the power board without the main connected. I don't remember if the Samsung needs the resistors or not, maybe Budm will chime in. You could check with your multimeter set in ohms (200 ) and see what the reading is between 5v standby and ground on main board harness.

[budm]

Re: New power supply, but tv fails to power on.

Here is the diagram of the power supply board, you do need resistor to force on the power supply on this one. I would run the power supply board without having the cable between the main board and the power supply board first and take the voltage reading of the standby power supply.
That device with the PFC is the inductor for the PFC Voltage booster circuit, it is not on until the PS_ON (POWER ON signal is applied.

[Marzog]

Re: New power supply, but tv fails to power on.

I can verify that without the main board connected, the ticking does stop. Oddly enough, the main board has a digital audio output slot with a red led in it. This led flickers at the same rate as the ticking.

Is this the view you were asking for btw?

[RCA2000]

Re: New power supply, but tv fails to power on.

If you have a pair of PS boards doing the same thing--and one is supposed to new--chances are both are ok.

now--you first need to comfirm all of your standby voltages are OK.

I KNOW_-Sam labels their PS boards with the voltages to be expected on the pins.

There should be a 5 volt line and/or a 3.3 volt line to the signal board at all times, possible a 12 or 13V. line too. Without these--nothing can happen.

CHeck to see if this is on the lines labelled (stby 5/3v) on the connector to the signal board.

If not--unplug the signal baord and recheck it . You likely would need to discharge the large B+ cap on the hot side---if the supply went into overcurrent shutdown--if the signal board is loading the PS voltages down.

If after you reapply power with the board unhooked and you then get standby voltages--the signal board--or something connected to it--is loading the supply down.

If you do get your standby voltage with the signal board connected--then you need to see if your run voltage is working.

That ticking sound you hear is likely the " overcurrent shutdown" mode of the SMPS. If it sees a very large load--it then gates the drive to the SMPS down to a low level--to prevent runaway current. If it did not do so--it would self destruct. This DOES happen on sony DV tv sets--if the h-out shots--there is NO OCP and the smps get s whacked instantly. Those in this business know what I am speaking about !!

ALSO--if this set uses a seperate backlight inverter--UNPLUG this--and then recheck your PS volts. I recently had a SOny LCD set--I thoght had a bad signal board, as it seemed ot be loading the PS and causing OCP shutdown--but I unplugged the BL connector and the set the tried to run and all voltages returned. Shorted MOSFET'S on the inverter.

So-check this out.

[RCA2000]

Re: New power supply, but tv fails to power on.

I can verify that without the main board connected, the ticking does stop. Oddly enough, the main board has a digital audio output slot with a red led in it. This led flickers at the same rate as the ticking.

Is this the view you were asking for btw?

If this is the case--you likely have a load on some line. I see a 5 volt and a 12.8 V output on that supply. I also see a "on off" pin--this is the one you need to use to force the PS on without being hooked to the signal board to test it. Usually--this needs to be hooked to the 5V. line-and the all run voltages should come up. It looks like the only switched volts on this is a 5v line. The 12.8 v. line comes right off of the diodes on the SMPS transformer--and not switched--so it should read in standby. the 24 volts goes to the inverter--and maybe the audio chip too.

You may have a shorted audio amp. also--make SURE there is no short on the speaker lines--such as a pinched line to ground or such.

[Caleb]

Re: New power supply, but tv fails to power on.

pin 3 is your standby voltage source, pin 1 is the power supply on, you will need to jumper pin 1 to pin 3 with a 1k resistor to turn the power supply on with out the main board connected. Then with your multimeter in dc voltage mode you can check the 12.8, 5.3 and 12v outputs on their respective pins. it is often easiest to do this by putting the resistor into the holes on the top of the connector an unplugging the other end, then you can also use a small wire into the other end to check each of the voltages.
Its not a bad idea as RCA said to unplug the speakers just in case one of them is shorted. Im curious what the resistance was going to the main board?

[cordy56sep]

Re: New power supply, but tv fails to power on.

Tech question on Phillips/Magnavox power supply board. Can power supply p/n ADPF24300R1P be replaced by P/n ADPF24300R3P? I can't see a difference in them but...
BTW... I don't know "where" else to address this, so forgive me if I'm wrong...please.

[Caleb]

Re: New power supply, but tv fails to power on.

@Cordy I didn't find any reference on the second part number but there is a repair kit available on the first board. It replaces 6 Capacitors C951, C952, C953, C921, C947, C957
and 4 Diodes ZD902, D904, D906, D908. It may be better to start a new thread on your tv.

[cordy56sep]

Re: New power supply, but tv fails to power on.

Thanks Caleb. Will do.

[Marzog]

Re: New power supply, but tv fails to power on.

Unfortunately, I don't have a 1k resistor just lying around, and I'm working two 8 hour shifts in the next two days. It'll be Monday before I can test anything really. Thanks for the advice though!

I did check the speaker cables and saw nothing wrong with them. I unplugged them from the main board and attempted to plug the tv in again. Sadly, I got the same result as before. However, the grounding wire from the power cord connection seems to be at an awkward angle, so I'll be investigating that closer soon.

[budm]

Re: New power supply, but tv fails to power on.

Clarification, the STBY5.2V is the always on power supply.
The 24V, 12.8V. 12V, and the 5.3V are SWITCHED power supplies generated from transformer TM801S that are turned on by the POWER ON/OFF (PS_ON) pin, same for the PFC Voltage booster circuit.
when QB851 received the PS_ON, it turns on OPTO PC801S which turns on the QB802 which is the 15.6V linear regulator, this transistor supplies the Voltage to run the PFC IC ICP801S, and the SMPS IC ICM801 (for the 24V, 12.8V, 12V, 5.3V supplies).
At this point you need to find out if the STBY5.2V has fluctuating output or not first by using 5 Ohms load to simulate 1A current draw, if you hear the ticking sound just by having the main board connected and the TV power switch is not activated, that means the standby 5.2V is ticking since the PS_ON is not present yet.
Right now it sounds to me that the main board is loading down the power supply. The key is that do you have steady STBY 5.2V without turning the TV on (you can look to see if PS_ON is present or not incase it turns itself on).

[Marzog]

Re: New power supply, but tv fails to power on.

I'm still at work for another 5 hours or so, but I'll try to test the PS_ON once I get home. How would I go about testing that anyways? Will I need the 1k resistor for that, where do I place the multimeter prongs, what setting should it be on, etc.

Also, for the test involving the 1k resistor, will any 1k ohm resistor do? The one I can obtain fairly easily are "1K Ohm 1/4-Watt Carbon Film Resistor" at my local radio shack. Will those do? Or does the wattage matter?

[Caleb]

Re: New power supply, but tv fails to power on.

1/4 watt is fine, as stated before the resistor will go between pins 1 and 3 on the large header of the power supply. you can check to see if you have steady standby voltage without the resistor -with you multimeter in dc volts, red lead to pin 3 black lead to ground screw. Dont slip or you will let out the magic smoke.

[Marzog]

Re: New power supply, but tv fails to power on.

Quick update: got the resistors, did test with jumping pin 1 to 3. When power is connected to the board, a single "tick" is heard. Tomorrow, or when I have more time, I'll get some readings for the other pins while the resistor is in place and report back here.

Also, I did what Caleb suggested and checked the standby voltage. I got a very steady 5.2v reading.

[budm]

Re: New power supply, but tv fails to power on.

Since the standby is steady, then you will need to check the DC Voltage right at the two legs of the main filter cap to see if it has steady DC voltage with more than 360VDC on the two legs of the cap.

[Marzog]

Re: New power supply, but tv fails to power on.

I'll test that when I get home tonight. I assume the main filter capacitor is the large black cap near the center of the board?

[budm]

Re: New power supply, but tv fails to power on.

Yes, the one with 450VDC rating.