Bad BN44-00264A PSU Board for Samsung LN40B610A5F LCD

[JFred]

Thanks to BudM and the following post, I was able to repair my dead Samsung LCD TV (https://www.badcaps.net/forum/showth...ung+BN44-00264).

I'm posting here to document the slight variations on the problem and the fix.

LCD TV Model: LN40B610A5F
Manuf. Date: 12/2009
Power Supply Board: BN44-00264A (schematic & pic attached)

Symptoms: TV went completely dead while watching. No audio, no video, no standby LED light

Diagnostic troubleshooting results on PSU board:
1) Fuse FM802S blown
2) Voltages on bridge rectifier BD801S looked OK:
- 122.3 VAC on AC side
- 170.3 VDC on DC side
3) Voltages on CNM802 all dead (i.e. Stdby, 5.3V, 13V)
4) Besides the blown fuse above, two MOSFETs and their two snubbing capacitors were found to be shorted. Their locations are shown circled on the attached pic.
MOSFETs: QI820, QI821
Caps: CI890, CI891

Replaced with the components shown in the attached table and TV works fine.

[DENNISMARTIN]

Re: Bad BN44-00264A PSU Board for Samsung LN40B610A5F LCD

Hi All, my Samsung TV fuse FS801S on BN44-00264A kept blown when turned on. My is operating on 230v. I had measured all MOSFET and no short was detected based on BudM and others advise on measurement.
Meassurements:
1) CP801S and CP802S = 6.3Kohm
2) CP803 and CP8810 = 5.3kohm

Measurements on LP801S
1) connected to Bridge Rectifier - to + was 7.0kohm.
2) connected to Bridge Rectifier - to LB802 was 7.0kohm
3) connected to Bridge Rectifier - to RP801 was 0 ohm
4) connected to Bridge Rectifier + to LB802 was 0 ohm

As I was not able to get the data sheet for this DC/DC Convertor LP801S, I not sure it was shorted..
Any advises from anyone will be greatly appreciated.

Thanks in advance.

DennisMartin

[DENNISMARTIN]

Re: Bad BN44-00264A PSU Board for Samsung LN40B610A5F LCD

Hi All,

Anyone can advise whether LP801S was normal or shorted based on the measurement or any other parts need further measurement.

Thanks,

DennisMartin

[infinityzxx]

Re: Bad BN44-00264A PSU Board for Samsung LN40B610A5F LCD

Thanks to BudM and the following post, I was able to repair my dead Samsung LCD TV (https://www.badcaps.net/forum/showth...ung+BN44-00264).

I'm posting here to document the slight variations on the problem and the fix.

LCD TV Model: LN40B610A5F
Manuf. Date: 12/2009
Power Supply Board: BN44-00264A (schematic & pic attached)

Symptoms: TV went completely dead while watching. No audio, no video, no standby LED light

Diagnostic troubleshooting results on PSU board:
1) Fuse FM802S blown
2) Voltages on bridge rectifier BD801S looked OK:
- 122.3 VAC on AC side
- 170.3 VDC on DC side
3) Voltages on CNM802 all dead (i.e. Stdby, 5.3V, 13V)
4) Besides the blown fuse above, two MOSFETs and their two snubbing capacitors were found to be shorted. Their locations are shown circled on the attached pic.
MOSFETs: QI820, QI821
Caps: CI890, CI891

Replaced with the components shown in the attached table and TV works fine.

Thank you so much JFred - That was what broke my TV as well

[Meins321]

Re: Bad BN44-00264A PSU Board for Samsung LN40B610A5F LCD

I have got a BN44-00264A too inside my 40" Sony but all my fuses are ok...

it's just the trv that powercycles on and off, the backlight comes on and it plays a sound then goes off again....

I concluded from other sources that you need to replace:
UP801S /ICP801 Power IC FAN7530
RP809/RP810/RP811/RP812 1M Ohms

i did recapp the whole powersupply with still the cycling on and off error and then replaced RP809 up to RP811 with a single 3M Ohm standard wired resistor, still cycling on and off...

now i wonder if i am on the right track to repair it, one of the 1M smd resistors was reading a bit low in the700k Ohms range..


Anyone had this issue with on and off cycling?

[johnboy1313]

Re: Bad BN44-00264A PSU Board for Samsung LN40B610A5F LCD

I have got a BN44-00264A too inside my 40" Sony but all my fuses are ok...

it's just the trv that powercycles on and off, the backlight comes on and it plays a sound then goes off again....

I concluded from other sources that you need to replace:
UP801S /ICP801 Power IC FAN7530
RP809/RP810/RP811/RP812 1M Ohms

i did recapp the whole powersupply with still the cycling on and off error and then replaced RP809 up to RP811 with a single 3M Ohm standard wired resistor, still cycling on and off...

now i wonder if i am on the right track to repair it, one of the 1M smd resistors was reading a bit low in the700k Ohms range..


Anyone had this issue with on and off cycling?

One (or more) of the inverter transformers is likely bad. Please post a picture of your power supply and a close up of each inverter transformer. There may even be a brown burn mark on the top of the suspect transformer.

[budm]

Re: Bad BN44-00264A PSU Board for Samsung LN40B610A5F LCD

@Meins321
FAN7530 is for the PFC Voltage booster circuit.
So What boosted Voltage do you have to run the power supply? It should be closed to 400VDC on the main filter cap.

[Meins321]

Re: Bad BN44-00264A PSU Board for Samsung LN40B610A5F LCD

i couldn't see any burn marks, is there any way to check the transformer itself?

Tried to picture them from top to bottom..see attached pics

The main caps show 390V if you plug the tv in, then it settles down quickly to 315~320V DC.

If you press the on button on the front the backlight goes on and the voltage shots up to 390V and stays there, while the tv plays start melody and cycles on and off with its backlight. Doesn't show any menu if i press the menu button :-(

should i take out the board again to look at the underside of it?

I could potentionally measure the resistance on the output side from the inverter transformer... but if they are still soldered in does it make sense?

Can i remove (or fake) the backligh ok signal for the motherboard, if it is the inverter running too hard?

Thank you for your fast imput and help guys i really appreciate it

[johnboy1313]

Re: Bad BN44-00264A PSU Board for Samsung LN40B610A5F LCD

It's possible you have one or more bad bulbs inside your panel.

https://www.badcaps.net/forum/showthread.php?t=29580

[Meins321]

Re: Bad BN44-00264A PSU Board for Samsung LN40B610A5F LCD

@johnboy1313
Thank you for that link... if the backlight is gone i will trash it for sure, replacing the ccfl is too expensive here in germany....

it would be nice to cut out the inverter and "fake" the backlight on is good signal, and then just use safely 12V LED strips to run it ^^

Anyone knows how to fake "inverter OK" to the mainboard? Maybe with some resistors on the powersupply output to get the same voltage levels as with a working inverter?

[johnboy1313]

Re: Bad BN44-00264A PSU Board for Samsung LN40B610A5F LCD

If you can follow the process that I used, you can eliminate one of the transformers and run the TV without trying to fire the dud bulbs. If you weren't in Germany, I'd send you some bulbs for the cost of shipping.

[alybruin]

Re: Bad BN44-00264A PSU Board for Samsung LN40B610A5F LCD

Thank you JFred! I had the same problem with the fuse keeps blowing out on the
BN44-00264A power supply board. I found your post, ohmed out the components and found the same shorts on the same components you described. I replaced them and now board is good. Thanks for sharing your work!

[kemi]

Re: Bad BN44-00264A PSU Board for Samsung LN40B610A5F LCD

Hi alybruin,
My problem seems like same as your problem.
Can you explain how to check voltages on bridge rectifier (BD801S- 122.3 VAC on AC side
- 170.3 VDC on DC side) and on CNM802 (Stdby, 5.3V, 13V)? If possible, please show me some pictures, ie, where to put - and + terminals.

Thank you very much.

[dskall]

Re: Bad BN44-00264A PSU Board for Samsung LN40B610A5F LCD

Two center pins will be ac. Outer pins are + and - dc. 5.3vdc Standby is on connector that runs from power to main board.

[jczarniak]

Re: Bad BN44-00264A PSU Board for Samsung LN40B610A5F LCD

@Meins321
FAN7530 is for the PFC Voltage booster circuit.
So What boosted Voltage do you have to run the power supply? It should be closed to 400VDC on the main filter cap.

Hi,
Got similar problem with my TV.
Backlight is on only for few seconds after switching TV on or
longer if in the TV settings you set the backlight on the very low level.
Power supply:
BN44-00264A
Checked the voltage on the two filter/PFC 450V/82uF caps:
Fluctuating between 382-402V when TV is ON
Standby: 332-346V
Not sure if that's what I should expect for this power supply.
THank you for any support.
Regards

[tbishop2]

Re: Bad BN44-00264A PSU Board for Samsung LN40B610A5F LCD

I replaced the components you did. Now it comes on and stays on but has NO backlight at all. Another bad component or are the bulbs not lining up while placing it back in?

[alllw]

Re: Bad BN44-00264A PSU Board for Samsung LN40B610A5F LCD

Thanks to BudM and the following post, I was able to repair my dead Samsung LCD TV (https://www.badcaps.net/forum/showth...ung+BN44-00264).

I'm posting here to document the slight variations on the problem and the fix.

LCD TV Model: LN40B610A5F
Manuf. Date: 12/2009
Power Supply Board: BN44-00264A (schematic & pic attached)

Symptoms: TV went completely dead while watching. No audio, no video, no standby LED light

Diagnostic troubleshooting results on PSU board:
1) Fuse FM802S blown
2) Voltages on bridge rectifier BD801S looked OK:
- 122.3 VAC on AC side
- 170.3 VDC on DC side
3) Voltages on CNM802 all dead (i.e. Stdby, 5.3V, 13V)
4) Besides the blown fuse above, two MOSFETs and their two snubbing capacitors were found to be shorted. Their locations are shown circled on the attached pic.
MOSFETs: QI820, QI821
Caps: CI890, CI891

Replaced with the components shown in the attached table and TV works fine.

A big thanks to JFred and all contributors on this forum helping others fix their electronics. I had the blown fuse fm802s and shorted MOSFETS. Caps were not shorted but I went ahead and replaced them. From your parts list I also ordered the fuse , caps and MOSFETS from Digi-key which I haven't purchased from in over 25 years. (this is just a hobby for me)
Now the TV set is working again and will not have to be recycled.

Thanks again....

[neilc6]

Re: Bad BN44-00264A PSU Board for Samsung LN40B610A5F LCD

Just repaired this power supply board for a LN40B530 LN40B530P7F LN40B530P7FXZA. Tv was dead and no standby light. Didn't realize there were two fuses until I watched the shopjimmy repair kit video for the power supply. FM802S and the two FETs were shorted. Snubber caps tested good. TV powered up after repair but power off, channel up/down and source buttons on the remote were not working. Factory reset and still the same. Firmware upgraded and all remote buttons working.