Samsung BN44-00214A Power Supply for LN32A450C1DXZA

[kenmoe]

I have done multiple searches and have come up empty, so I have decided to post here. I am currently working on a Samsung BN44-00214A. When I originally got the tv, it would turn on for a few minutes then shut off. It would not turn on again unless it was unplugged from the wall for several hours. After checking voltages on the power-supply board, I have been able to figure out that the standby circuit works fine, but the 12v is showing 4v and the 24v rail showing 8v. This is happening even when the power-supply is not hooked up to the mainboard and getting the power on signal back from the mainboard. Any insight would be wonderful, Thank you!

[nomoresonys]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

Apart from the obvoius things like checking electrolytics and for dry solder joints and for broken windings in the transformer, you should also check your feedback circuit. If something is wrong with the resistor voltage divider or optocoupler in the feedback circuit, this could have the effect of a lower output voltage than expected.

[kenmoe]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

I guess my question is what would cause the power supply to supply power from the 12v and 24v rail even when the power supply should be off. I have checked the obvious things like caps, dry or cracked solder joints.

[nomoresonys]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

Faulty voltage regulator?

[nomoresonys]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

https://elektrotanya.com/?q=showresult see if you can grab a service manual from here.

[vinceroger69]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

schematic

[kenmoe]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

Yes, I have the schematic. I think I'm in over my head. Maybe I should just order a new board

[nomoresonys]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

I think you're in the right area.

[vinceroger69]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

i would wait and see if budm has any tests you can do he may of worked on one of these psu s before or seen this fault before

[kenmoe]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

that would be great

[nomoresonys]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

Sent you a message, says last one.

[nomoresonys]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

Not sure how you tested, did you jumper ps with one of the 5.3, then see if your 12 volts are present.

[kenmoe]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

I have voltage present at the 12v and 24v pins when the board is not jumpered or attached to the mainboard. But the voltage present is 1/3 of what it should be when powered on by the standby.

[kenmoe]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

Am I wrong in assuming there should be 0v when not jumpered or attached to the mainboard

[nomoresonys]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

Did you check them with all boards hooked up and tv powered on?

[budm]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

I have done multiple searches and have come up empty, so I have decided to post here. I am currently working on a Samsung BN44-00214A. When I originally got the tv, it would turn on for a few minutes then shut off. It would not turn on again unless it was unplugged from the wall for several hours. After checking voltages on the power-supply board, I have been able to figure out that the standby circuit works fine, but the 12v is showing 4v and the 24v rail showing 8v. This is happening even when the power-supply is not hooked up to the mainboard and getting the power on signal back from the mainboard. Any insight would be wonderful, Thank you!

Can we see the pictures of the whole power supply board?
1) This PS board uses those bad brown glue which is corrosive and conductive.

2) This PS board does not have pull-up resistor to force on the power supply when not connected to the main board so the switched 12V for the audio amplifier and the 24V for the inverter should not be present. So we need to verify for sure that is not error in reading when board is not connected to the main board.

3) Disconnect the cable that carries the 24V to the inverter board and then check the 24V output pin of the power supply board to see what you get and see if the TV will stay on and be able to turn it on and off or not (You will not have backlights of course).

4) If you still having problem turning TV on and off without 24V cbale connected then we need the stand by Voltage reading to see if it is steady at around 5V or not when the TV is turned on, then we need the PS-ON pin reading when the TV comes on and after it goes into shut down by itself.

5) We can also do the force on the power supply with the resistor and then you need to check and see if you do have 380V or so measured between the two legs of the main cap which you will have to be really careful since we are making measurement in the deadly side of the circuit. The 12v/24v power supply needs that boosted Voltage to work.

6) This board is known for bad DC BLOCKER/COUPLING cap CN808 (0.16uF 630V) that will cause low 12V/24V output due to losing its capacitance.
Pictures provided by shopjimmy.

[nomoresonys]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

Look at CP801 very closely, see if it has any bulging or leaking.

[kenmoe]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

I should have mentioned that i did remove all the glue from the board as I had also read it can become conductive.So I put the PS back it the tv, hooked up the main board but left the inverter board disconnected. The TV did not turn on. There is a steady 5.2v at the stb pin, and a red light on the front of the tv. There is 7v present on the 24v pin, and 4v present on the 12v pin when inverter board is connected and diconnected. Both the 12v and 24v readings are not very stable, while the stb is. I didn't get any reading from the pwr on pin, even while pressing the power button.

[kenmoe]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

When CNM801 is connected i am reading 3.5 v at pin 5 or the 24v detect pin. When disconnected, I am getting a reading of 1.5v on the power supply and 5v coming from the mainboard.

[budm]

Re: Samsung BN44-00214A Power Supply for LN32A450C1DXZA

"he TV did not turn on. There is a steady 5.2v at the stb pin, and a red light on the front of the tv." So the POWER LED on the front of the TV did not change state and no startup chime either when the TV is turned on and off?