POWER SUPPLY BN44-01056A Power fluctuation ON MAIN CAPACITOR

[bohaboha]

As mentioned above, the power goes down quickly from 394V to 374v then up and down with the same value, it usually is steady at these capacitors for everything to work flawlessly. It is very difficult to decipher what is written on this board the manufacturer has chosen white text on a bright yellow surface. Wondering what could be causing this power loop.

[bohaboha]

No one who has had the same problem who can give me any suggestions

[stj]

could be the cap is shit or a PFC circuit problem

[CapLeaker]

What stj said! Start with the main filter capacitors.

[bohaboha]

could be the cap is shit or a PFC circuit problem

Hello i do not have a performant capacitor tester am using a very simple digital component tester and my multimer that also have that option the capacitor 2 of them are 500v 82 uf i found :
153,7uf
ESR 0.70 ohm
lost 1.4%
test on board
since they are 2 i think it is ok

[CapLeaker]

Is that board working or do you have any problems beside the PFC being wonky? I do notice that some caps are not looking good (sleeve shrunk) like the first pic top left 4 capacitors for example.

[bohaboha]

Is that board working or do you have any problems beside the PFC being wonky? I do notice that some caps are not looking good (sleeve shrunk) like the first pic top left 4 capacitors for example.

normally the board is working because the backlight comes on when i disconnect the mainboard and the 12,4.5 and 3.2V are present on the connection to the mainboard but what is strange on this power supply is all the cold side have a very high voltage all over 220v,180v all that left side . that why i took some test on those caps s and find that the power is looping from 399v to 374 down and upp
a bit strange

[CapLeaker]

Well the backlight LED’s strings need current controlled high voltage DC somehow. It shouldn’t be surprise.

[bohaboha]

Well the backlight LED’s strings need current controlled high voltage DC somehow. It shouldn’t be surprise.

yes i understand but on this board there is only Hight voltage all over the cold side the 12v, 3v and the 4.5v are only on the contact pins that goes to the main board.
about that voltage looping from the main capacitors it applies only when the mainboard is connected. Otherwise it is a steady 394v .
I think it says that there is something that is not right with the Mainboard so I leave the power supply alone .I wait for the mainboard that is on its way and see what happens or do you think there is something with it ?

[CapLeaker]

Disconnect the main board, and put a load on the output rails something like light bulbs etc. See if you get that PFC to loop again.

[stj]

where are you grounding the meter?
the primary and secondary probably arent linked.

[bohaboha]

where are you grounding the meter?
the primary and secondary probably arent linked.

For the main capacitors on them directly . for the primary negative of the capacitor and the secondary the chassis

[bohaboha]

Disconnect the main board, and put a load on the output rails something like light bulbs etc. See if you get that PFC to loop again.

the load must be 12v like a car bulb ? only 12v on the outputs rails

[CapLeaker]

Sure... you can put 12v incandescent bulbs on the 5V rail, they just dim a bit, but will use some current!

[bohaboha]

Sure... you can put 12v incandescent bulbs on the 5V rail, they just dim a bit, but will use some current!

i do not have any of those just now I'll see if I can find anything in the garage, I'll get back to you a little later

[bohaboha]

Hi all on this PS there is no full specification of the connector CNM801
1)GND 2) ANA_DIM
3) A13V 4) N C
5) A13V 6) PWM_BLU
7) A13V 8) POWER_ON
9) A13V 10) GND
11) GND 12) GND
the 13V is present 12.93V
there is no indication for 2,4,6 and 8 what value should be
For the STB and something named ON in the front of the CNM801 referring to 3 Jumper there must be 12.3V and 12.35V i do have 12.93V
CapLeaker with a load i used a a 12V car bulb on CNM 801 and no loop just 394V steady.
the question now is to where belong the 5V and 3.3V and a strange 2.4V in the bottom row of CNM801.
the PSU seems to be ok because when i disconnect the Mainboard the Backlight is on but still the Mainboard must have the right voltage from the PSU and that 2.4v is enigmatic

[CapLeaker]

Easy. Ana-dim is the dimming signal for the backlight from the main board to the PSU
PWM-BLU is the signal from the main board to the PSU to turn on the backlight
Power on = PSon comes from the main board and tells the PSU to turn all voltage rails on.
These values are you measured are o.k. The strange voltage probably belongs to the dim signal. You said pin 4 is N C or not?

[bohaboha]

Easy. Ana-dim is the dimming signal for the backlight from the main board to the PSU
PWM-BLU is the signal from the main board to the PSU to turn on the backlight
Power on = PSon comes from the main board and tells the PSU to turn all voltage rails on.
These values are you measured are o.k. The strange voltage probably belongs to the dim signal. You said pin 4 is N C or not?

for pin 4 it says N.C but the plug has all its 12 wires that go to MainBoard. That strange voltage of 2.4 is not stable and it does not say what actual denomination it should have, nor numbers 2,6 and 8.
then what is that ON 12.35 just in front of the contact CNM801

[bohaboha]

Hello again, how is the Mainboard affected if it is not supplied with absolutely the right power, example 3.01V instead of 3.3V or 4.3V instead of 5V, do board works as it should ?

[CapLeaker]

As long as you take the main board off the PSU and "force" the PSU on and all the voltages are correct, it is safe to say you got a main board problem. We don't know what the TV model number is, nor we know what the TV main board does or doesn't do (symptoms why you think the main board is bad). Also the voltages you talk about, we haven't got a clue what pins they correspond to.
Some pins for example the dim pin voltage depends on what the back lights are set to. The PSon and BLon pin should be very close or the same as STBY voltage. Dim, PSon, BLon comes from the main board and tells the PSU what to do. The only voltage originating by the PSU and sent to the main board is STBY.
Maybe the main board has a short somewhere and dragging the voltage down. Who knows. Too hard to tell if we don't see the whole picture or don't get told the whole story.
Maybe make a new thread in the TV section, since you got main board trouble.