Samsung PS50A656T1FXXC PSU: BN44-00222A

[Bobo360]

TYPE: PLASMA
BRAND: Samsung
MODELLO: PS50A656T1FXXC
Chassis : F48A(P_Euro_FHD)_Topaz
PSU: BN44-00222A

(I can not find schematic)

Defect description:
I feel the relays that are constantly attacking and disconnecting.

I tried to disconnect the X and Y cards, the problem persists.

however, disconnecting all cables does not do anything. I do not hear any relay.

In the lower right-hand connector (the one connected to the main in the bottom right-hand corner) I find the standby voltage 5.22V.

As soon as I connect this connector (CN801) I hear the relays that do attack and detach and then I discovered that the card near the heatsink by a kind of code with the green led.

Two cyclic flashes. Do you know what it refers to and if there is a diagnosis table?
(I attach the video)
Video

I removed the CS809, the condenser seems good to me.

What other tests can I do?

Thank you

[Bobo360]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A

Hi guys, I guess that only now I realized that the power board works.

After almost dismantled piece by piece the feed card, checked Mosfets, Electrolytic capacitors and replaced those that in my opinion had strange values, diodes and resistances ....

I reassembled everything and nothing has changed.

So I fix everything, but a little annoyed I said, I have to start the power supply without having anything connected, so if I do not have tensions I order a new card. But instead....

Then only power supply connected without X and Y card or other cables. I connected the CB802 cable, the one that goes to the logic board below, but without connecting the other end.

Connecting PS_ON to GND and VO_ON to 5.3V, but the power supply does not start.
Then I look at the CB801 connector where it is connected to the motherboard.
So I connect in the CB801 PS_ON to GND without connecting it to the mainboard.
While on CB802 connected VS_on to 5.3V
Now I do not hear relaying interviews, and I see that the power supply goes, all the voltages are present.

Then I continue with the tests by making stress on the tensions, I wait for you to download everything before putting hands on.
Disconnect the main from the login tab so you do not have any links.

Connect CB802 to the logic board below, leaving the jumpers PS_ON and VS_ON unchanged.
In the logic board I jumpered the famous pins 3 and 4.
Food all, I do not hear the power supply board relays,
I see on the TV that seems to light up and the green LEDs on the logic board light up.
I remove the alimntatore, because I wanted to see if removing the VS_ON connection the logic board worked.

But from now on, both when I connect the logic board or the motherboard, I always hear the power supply relays that are going on and off as before.

Disconnecting these two cards, the power supply works.





Can I do a few more tests to figure out if at least the logic board is working?

Because if I only connect the motherboard to the power supply, it's the fault. Like now with the logic board.

I hope in an advice, thank you

PS:
Maybe while the logic board was working, did I remove power? boh

[Bobo360]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A

Hi guys, in all this absence I have done countless other tests.

I have found it seems that the main "should be broken" and the logina no.

I say this because the power supply I managed to detect a buzz, which apparently I do not have the 5.3V output, oscillating between 4.6V and 5.3V that send the main and logic trip.

When the buzzing ends the voltage is stable and is at 5.3V.
But at this point I can not hot-link the rest of the cards.

Now this buzz will be given by the high frequency transformers? from inductors or capacitors?

Can you give me some advice / advice on how to search?

I have the card of a similar power supply the BN44-00237A, can it help somehow?

Thank you

[tvtimmy]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A

Try running the test patterns. Unplug the cable going from the main board to the control board. On the control board there are 4 pins, short pins 3 and 4 then plug in the tv.

[Bobo360]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A

Try running the test patterns. Unplug the cable going from the main board to the control board. On the control board there are 4 pins, short pins 3 and 4 then plug in the tv.

Thanks for the reply, but at the moment I can not do this test.

From the power supply I can not stabilize the 5.3V. There is a lower voltage. Type 4.4V - 4.7V.
I was checking the CX834 and CX835 2200uF 10V but they look good.

the Schottky Rectifiers F20SC6 could be?

[Bobo360]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A



Could it be the L6725 controller and the two power mosfets for DC / DC conversion (25H3LL)?

Can I test them before I take them down?
or can I measure the hot tensions? (when I give the PS_ON command to the card)

Thank you

[R_J]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A

Have you tried the other power supply (BN44-00237A)? it should work The substitute board for a BN44-00237A is a BN44-00222A
The Alarm signal for 2 blinks is problem with 5.3V on power supply
The ALARM SIGNAL table is on the board next to the ACN802 module

Also what is the Va voltage?

[Bobo360]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A

Have you tried the other power supply (BN44-00237A)? it should work The substitute board for a BN44-00237A is a BN44-00222A
The Alarm signal for 2 blinks is problem with 5.3V on power supply
The ALARM SIGNAL table is on the board next to the ACN802 module

Also what is the Va voltage?

Thanks for the reply,

Before buying the BN44-00237A, I would like to try to repair.
If it is possible. I'm doing a lot of attempts, but first I was wrong and I was looking for the problem away from 5.3V.

The Va seems to be regular, it gives me about 56 / 57V.

In your opinion, the controller L6725 and / or the MOSFET ST25H3LL could be?
What could I try?

Thank you

[R_J]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A

From post#3

I have the card of a similar power supply the BN44-00237A, can it help somehow?

I thought you already had this board.

Your power supply is working So I do not believe there is a problem with L6725 or the fets, If they were bad you would not have any voltage.
Check the voltage on CX823 or CX824 to see if it is ok and stable. (you can check this voltage on the anode of DX809 near CN805)

The Va voltage comes from the same transformer as the 5.3v so if it is stable the 5.3 should be also.
Sometimes CX810 (square blue capacitor) can be bad (47nf/1250v) Check that it is not cracked or bulging.
You may also have a fault that is loading down the 5.3 volt line.
Here is a good picture of the bottom of the board.

[Bobo360]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A

Your power supply is working So I do not believe there is a problem with L6725 or the fets, If they were bad you would not have any voltage.

Thanks for explanation, very useful for learning.

Check the voltage on CX823 or CX824 to see if it is ok and stable. (you can check this voltage on the anode of DX809 near CN805)

I will do these tests and let you know.

The Va voltage comes from the same transformer as the 5.3v so if it is stable the 5.3 should be also.
Just to be sure It is the 5.3v on CN805 that is low?

for the transformer I think I understand.

For the 5.3V I have always measured them {CN805} . But even in the other places they do not give me the 5.3V.{CN801, CN802}
I hope I have understood correctly.

[R_J]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A

In post#6

Could it be the L6725 controller and the two power mosfets for DC / DC conversion (25H3LL)?

Yes it could be one of the fets. I did not know at the time those were the parts you were talking about as I don't know the part numbers on the components, I thought you were refering to the parts in the primary circuit. I can only go by whats marked on the board ie: qx807 etc.

The anode of DX809 is connected directly to the two capacitors of CX823 & CX824, the transformer supplies DX805 diode which is the source for the 5.3 volts.
It is before the two QX807 and QX808
Also check the board for cold solder joints like this thread https://www.badcaps.net/forum/showthread.php?t=57754

[Bobo360]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A

First of all, thank you for your support.

The Va voltage comes from the same transformer as the 5.3v so if it is stable the 5.3 should be also.
Sometimes CX810 (square blue capacitor) can be bad (47nf/1250v) Check that it is not cracked or bulging.

The Va, the last time I tried it, it worked. I have to try again.
is it more correct to check it as soon as I resolve the 5.3V?
The CX810, I had disassembled it long ago, I remember it was good.
I could verify it again.

The anode of DX809 is connected directly to the two capacitors of CX823 & CX824, the transformer supplies DX805 diode which is the source for the 5.3 volts.
It is before the two QX807 and QX808

I will do these measurements and let you know.

Also check the board for cold solder joints like this thread https://www.badcaps.net/forum/showthread.php?t=57754

Unfortunately I'm not as lucky as him, I have good welds.


Last thing I want to say is this:
I feel a kind of "buzz" in the transformer indicated with the arrow.
But I'm not 100% sure.
When, after a while, the 5.3V stabilized; the "buzz" ended.
I hope I have given some other input.
Thank you

[R_J]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A

That transformer is the P.F.C. transformer, check the pfc voltage on FS803. The pfc voltage should be around 400v, measure it and see if it changes.
Did you check the two fets on the 5,3 volt output? if one is shorted you would still get 5.3 volts but it would likely vary.

[Bobo360]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A

That transformer is the P.F.C. transformer, check the pfc voltage on FS803. The pfc voltage should be around 400v, measure it and see if it changes.

Yes, I measured. With PS_ON connected to ground, on the two electrolytic capacitors, I find 396 Volt. I think they are ok. What do you say?

Did you check the two fets on the 5,3 volt output? if one is shorted you would still get 5.3 volts but it would likely vary.

Yes, I do not think there is a short circuit.

Returning to what you asked me some time ago:

Check the voltage on CX823 or CX824 to see if it is ok and stable. (you can check this voltage on the anode of DX809 near CN805)

I checked, at that point the voltage oscillates between 9.08V and 9.30V.
Therefore we can exclude the controller (L6525) and the two mosfets QX807 and QX808 (25H3LL).
right?


From what I can see, first there is only the DX805 or even the transformer first.
In your opinion what measures can I do?


I enclose the photo of all the measurements made today.

[R_J]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A

What is that voltage D5.3 if the power supply is connected in the tv. If there is no load on the D5.3 I can not see why it would be changing.

[Bobo360]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A

What is that voltage D5.3 if the power supply is connected in the tv. If there is no load on the D5.3 I can not see why it would be changing.

D5.3V indicates the voltage at 5.3V, as shown in the table.

I have no card collagata to this power supply, I will reconnect them if I can stabilize the 5.3V.
I would not break other cards. (I hope I have not already broken them.)

Since the transformer that generates 5.3V, it also generates the Va (57V) and is stable.
Can I rule out that it is the fault of the transformer and all that is on the primary side?

Can I control the CX823, CX824 and CX285 and the DX805?
In your opinion could it be one of them?
I think an oscillating tension could be a condenser, what do you say?

But the following points shown in the picture, can I measure them with a multimeter?


Thank you


PS:
When I removed the capacitors: CX834 and CX835, I measured them and:
CX834
ESR=0.08 OHM
Vloss=1.5%
C= 2316uF

CX835
ESR=0.09 OHM
Vloss=0.6%
C=2278uF

[R_J]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A

You need a scope to measure those points indicate by the yellow arrows, that is high frequency a/c (20-50 khz) Can you place a load on the 5.3 volt line? you can use a 5Ω 5 watt resistor to draw about 1 amp

[Bobo360]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A

You need a scope to measure those points indicate by the yellow arrows, that is high frequency a/c (20-50 khz)

Unfortunately I do not have an oscilloscope.

But I disconnected and tried the following components.
CX823 = 924,1 uF
ESR= 0,18 ohm
Vloss=1.3%

CX824 = 918,8 uF
ESR= 0,17 ohm
Vloss=1.3%

CX825 = 1040 nF
ESR= 3,9 ohm

I can think they are good and I have put them back together.

I said, I did not have the osciloscope. I used the Wavetek Meterman 34XR multimeter. I attach pdf.

I performed the following tests, with the points shown in the figure:
1-3 V=379mV RMS; Hz=53,6Hz; Duty cycle=48,1%.
2-3 V=378mV RMS; Hz=53,6Hz; Duty cycle=48,5%.
1-2 V=3,626 V RMS; Hz=53,6Hz; Duty cycle=47,7%.
I do not know if they can be useful, but I'm reporting them anyway.

Check the voltage on CX823 or CX824 to see if it is ok and stable. (you can check this voltage on the anode of DX809 near CN805)

I tried again to measure and gave about 9 volt.

Can you place a load on the 5.3 volt line? you can use a 5Ω 5 watt resistor to draw about 1 amp

This is a test I can do.

PS:
Today the very stable tension, very often the 5.3V came out.
Perhaps because the capacitors are unsoldered and resoldered? boh.

PSS:
When the tension is unstable, I feel a sort of "tic tic" at the DX805. Do you suffer from 50kHz?

PSSS:
DX805 -> F20SC6 Schottky Rectifiers, Do you know a better known equivalent?

PSSSS:
Since the 5.3V transformer is the same as the 57V, we can rule out that it is him. Or it is not said!

If you have any other suggestions, I'm grateful.
And all the advice you give me.
I always learn something more.

[Bobo360]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A

I'm back.

I changed all the electrolyte condensates or almost.

In the 5.3V line replaced the CX823, CX824 and CX826

In the VG line I changed the CX820 (47uF to 25V)

In the Va line, I changed the CX811 and CX812

and then in the 12V line I changed CX822.

I would miss the CX834 and CX835 to complete the 5.3V. I have them. Do I replace them?

Now in stanby the tensions are stable.

As soon as I put the 5 Ohm resistance at 5Watt.
The powered went into protection, and the relays attack and detach.
Giving me the error of the 2 flashes as an alarm.
Will it be the DX805 then? I replied a Schottky MBR20220CT.

Can I test the resistance even with Va? With a 120 Ohm resistance?

Or tell me.

[R_J]

Re: Samsung PS50A656T1FXXC PSU: BN44-00222A

The 5.3 volts should supply 7 amps, 5Ω across it would be about 1 amp.
The Va should be able to supply 1 amp, 120Ω should draw about 1/2 amp. If that shuts down the power supply it is time to look at the primary of that circuit and why it can't supply the curent.
If cx810 goes bad or weak it can cause this issue, If you don't have a replacement I would try and exchange it with either CS810 or CS811 and see if the 5.3 becomes stronger