Samsung LE46B650 leds turn off in less than a minute.

[fixitforfree]

TV itself is working fine otherwise. Disconnecting AV board shows the same behavior. Typically LEDs will be turned off in about 10 seconds.

IP board is a BN44-00265A. I found a bad Capacitor and replaced it.
Near that Capacitor is a Transformer: IP-N46-PFC which looks burned but it could have been from the Capacitor nearby.
I measured 13.x V on the primary Side and nearly nothing on the secondary. I suspect I would have to replace it but I am not sure about that. Both coils have next to no resistance (0.001 Ohm).

Trying to find a replacement however gave no results on search engines. Maybe someone has an idea on which transformer could replace it? Sadly I could not find a schematic on BN44-00265A.

I have read about older CCFL pulling more current. That could explain the shutdown of LEDS too... replacing the transformer to me looks more promising at the moment.

[nomoresonys]

Re: Samsung LE46B650 leds turn off in less than a minute.

Those are good clear pictures, can you post one of the underside?

[RJARRRPCGP]

Re: Samsung LE46B650 leds turn off in less than a minute.

Looks like a CCFL TV.

[nomoresonys]

Re: Samsung LE46B650 leds turn off in less than a minute.

See if you can locate and test a fuse on inverter board, maybe test the other components on inverter too, could also ohm out the little transformers on inverter too, they should all be similar when measured in ohm mode.

[fixitforfree]

Re: Samsung LE46B650 leds turn off in less than a minute.

Looks like a CCFL TV.

You are absolutely right. Its CCFL. Sorry for the confusion.

[fixitforfree]

Re: Samsung LE46B650 leds turn off in less than a minute.

Those are good clear pictures, can you post one of the underside?

Sure thing!

[R_J]

Re: Samsung LE46B650 leds turn off in less than a minute.

That transformer is the pfc transformer, it should be ok, Check the voltage across one of the main filter capacitors (100µf/450v), when the tv is in standby it should be (based on 230vac line voltage) around 325vdc, when the tv is powered ON it should rise to about 385vdc
The BN44-00265B schematic should be close.

[nomoresonys]

Re: Samsung LE46B650 leds turn off in less than a minute.

Inverter testing there, heed HIGH voltage warning: https://www.youtube.com/watch?v=oE6K4xBVweA

[RJARRRPCGP]

Re: Samsung LE46B650 leds turn off in less than a minute.

You are absolutely right. Its CCFL. Sorry for the confusion.

Those rectangular transformers where you can easily see some of the wire wounds, along with an extra high-voltage warning, screams CCFL.

[fixitforfree]

Re: Samsung LE46B650 leds turn off in less than a minute.

nomoresonys@: yes, that is a very nice video on how to find a faulty CCFL. Since I have measured all transistors on the inverter board and they all had the same resistances within 5% deviation or so I suspect a faulty Lamp at this time.

@RJARRRPCGP: during writing my problem report I started to realize it is not a LED TV, but forgot to adjust to that.

@R_J: did you mean the voltage of + and - of the 450V Capacitors? Because strangely enough I measured only 7V and started to think my voltmeter is faulty.

So now I want to measure voltages on the HOT side but before that I want to make sure not to electrocute myself or the TV.

In that video @nomoresonys mentioned the guy wrote he used the chassis as ground. From what I have heard one should only use the chassis for COLD.

The TV, when cold takes much longer (maybe 2 minutes) until it turns CCFLs off.

[dskall]

Re: Samsung LE46B650 leds turn off in less than a minute.

All measurements on hot side of board are referenced off of neg. terminal of main capacitor. That is for all measurements after bridge rectifier. All measurements on cold side will be regular ground points on cold side of board.

[fixitforfree]

Re: Samsung LE46B650 leds turn off in less than a minute.

Thank you man, for clearing that up!

[nomoresonys]

Re: Samsung LE46B650 leds turn off in less than a minute.

Yep, that video IS what you want to follow if you have a bad lamp, it takes the bad lamp out of the equation. It doesn't work on all tvs but the ones like yours with many mini transformers on the inverter it works for, I did one last year worked fine, down one tube but like he shows there, you will not notice it unless you look real hard. Watch closely he explains how he finds the problem, when he powers up the bad one jumps way up in voltage compared to the others, right before shutdown.

[nomoresonys]

Re: Samsung LE46B650 leds turn off in less than a minute.

Similar video there by another great tech and very good teacher on youtube: https://www.youtube.com/watch?v=Dh01...D4L_&index=943

[fixitforfree]

Re: Samsung LE46B650 leds turn off in less than a minute.

Similar video there by another great tech and very good teacher on youtube: https://www.youtube.com/watch?v=Dh01...D4L_&index=943

Very informative video - good explanations. I liked this one very much.

Like him I placed voltmeter to AC and used chassis for ground.

So here are my observations:

- PIN4 of the little transformers go to the feedback circuit.
- Whenever I start to measure voltages on PIN4 it starts at about .4V or less and drops to 0 rapidly... why???? It does not for him.....

- connecting ground of voltmeter to - (minus) of one of the two 450V/100uF capacitors and trying to measure voltage at measure dots on HOT side reveals about 132V but instantly causes backlights to go out, voltage of 132V however, stays.

I am bit confused here - if the voltage is still there then what causes the lamps to go out. Maybe because of the capacitors charge I still have voltage but no current?

- Not 100% certain on this one: Feedback1 and Feedback2 showed 0V, or at least when I checked them. Would I have to go back to DC on voltmeter for them? It seems plausible to me....

I am assuming the machine powers up.. gets voltage... the power boards shuts down and the machine will run for a few more moments on capacitors current? Could that be?

[nomoresonys]

Re: Samsung LE46B650 leds turn off in less than a minute.

I think it's best to do the ground out like he did there, to get the right one, that's also how I found my bad ccfl tube, don't really have to solder a post on there, holding the probe in place will do it, when it stays on you found the bad tube.

[dskall]

Re: Samsung LE46B650 leds turn off in less than a minute.

- connecting ground of voltmeter to - (minus) of one of the two 450V/100uF capacitors and trying to measure voltage at measure dots on HOT side reveals about 132V but instantly causes backlights to go out, voltage of 132V however, stays.


Any measurements you are taking on the inverter board are to frame, Or cold side. On your backside picture of power board. Everything inside the black line is HOT side. Everything else is referenced to frame ground.