Samsung LNT4053H BL ISSUR

[jkb242]

Re: Samsung LNT4053H BL ISSUR

Which version? A, B, C, or D?
http://www.shopjimmy.com/catalogsear.../?q=BN44-00167

It the A version very sorry I missed this when first requested. I just notice this designation today sorry.

[jkb242]

Re: Samsung LNT4053H BL ISSUR

Again thanks to all for assistance and apologize for my oversights in some of the questios asked.

The new problem I reported was today requesting additional assistance was due to a troubleshooting 101 oversight on my part. When I attempted to measure the pulse rate with my DVM at the GATE OF ONE OF THE MOSFETS Q1801, the set powered off. What actuall happened was SOMEHOW THIS TRIPPED THE AC breaker in the house, unknown to me at the time so it appeared the set now had no STDBY power. I discovered the set had no AC FEED and reset the breaker. So still no backlight but back to normal elsewhere with SDTBY and sound.

IF THE TWO CCFL HELICAL LIGHTS WORK ONE EACH OF THE TWO HV leads to the inverter board, then the issue must be in the inverter board. I've examined it closely but four nothing obvious. I will need to disconnect the inverter board from the power board to connect the two test lamps but this also leaves no FB signal from thr inverter board to power board. Without this FB, will the power board generate the HV bias to light the test lamps??

[budm]

Re: Samsung LNT4053H BL ISSUR

Please see post 16, I need the DCV reading of that small connector on the balancer board: the LD pin and the 12V pin to see if there is an error signal or not.

[jkb242]

Re: Samsung LNT4053H BL ISSUR

Hi to all involved in attempting to support me in repair of this Samsung.

After reading som comments shared by others on this forum, concerning the substitution of a low wattage CCFL bulb connected to the power/inverter board in place of the lamps in the to determine that the power/inverter board is eith at fault or something else. I'm not sure this substitution is a good idea. Budm mentioned as well that this test might not work and I feel there could be risk to the power board. Since this set uses a balancing board(from Budm) which is the interface to the sets internal lamps, there are likely different troubleshoot procedures I need to follow to isolate the root cause of the BL failure. The power board number is a BN44 00167 "A" version REV 1.1. The 385VDC bias appears as required. Beyond that I'm really stuck in deterring the actual cause of the issue. Indeed, the lamps do come on momentarily when viewing from the back of the set but they don't stay on long enough to show any readable screen in the menu mode. They turn off within ~ .5 seconds of initially starting and remain off but I have sound and an otherwise normal start. I would be delighted to hear from any member as to how to proceed in locating the root NO BL issue.

Thanks so very much!

[budm]

Re: Samsung LNT4053H BL ISSUR

Well, I am still waiting for the DCV reading on the connector CNI806 on that power supply/inverter board.
12V pin and the LD pin.

[jkb242]

Re: Samsung LNT4053H BL ISSUR

Sorry indeed I missed miss understood that request. Will posy in a few minutes.

Thanks!

[jkb242]

Re: Samsung LNT4053H BL ISSUR

12v pin 12.02
LD 10.21, at the moment LCDS flash on, drops to 1.3v

[budm]

Re: Samsung LNT4053H BL ISSUR

12v pin 12.02
LD 10.21, at the moment LCDS flash on, drops to 1.3v

So the LD drops down to 1.3V? That means the LD (Lamp Detection) circuit has detected unbalance condition due to one or more of the lamp is bad, or bad balancer transformer (not very likely).
For normal operation, LD should be around 10~11VDC.
You can watch this video: same setup as your TV.
https://www.youtube.com/watch?v=oE6K4xBVweA

You can learn about backlights system used in SONY/SAMSUNG in the attached PDF.

[jkb242]

Re: Samsung LNT4053H BL ISSUR

Yes at the moment the BL comes on but returns back to 10.21 once they are off again. Maybe I did not explain that very well.

[budm]

Re: Samsung LNT4053H BL ISSUR

You should test those Voltages as shown in the Video. The LD should never drop unless it is triggered by the fault.

[jkb242]

Re: Samsung LNT4053H BL ISSUR

Hey BudM, the attachment is awesome and really helps with a good basis bor undering the Balacing approach used in some LCD TV's. Still reading and studying this thanks a million!

I had seen the YouTube video which I found most informing all all I saw. I did not have be familiarization then I have now, but did indeed followed his suggested measurements of the "balanced" condition. I did not at the time find significant differences between the coil/lamp voltages as shown in the video but I will return to this procedure again today since it appears the power board is likely OK but as you stated, in determing which transformer or associated lamp is suspect. Hopefully if I have only one, for example, I can bypas that lamp as shown in the video so that It might be possible to use the set.

Again, thanks a million for the great assistance. I'll post my findings later today or tomorrow.

[jkb242]

Re: Samsung LNT4053H BL ISSUR

Solved this issue....many many thanks to budm and to norcal715 for many great posts and the dedication to this community and this effort.

Kudos to these very talented dedicated professionals!!

[budm]

Re: Samsung LNT4053H BL ISSUR

So what did you find wrong, bad lamp?

[jkb242]

Re: Samsung LNT4053H BL ISSUR

Indeed, sorry I did not elaborate in more detail.

As provided in the video from Norcal715, the test points for each transformer for pin 2 showed consistent readings of 0.09 to 0.13, except the one associated with the weak or bad lamp. It showed 0.52. I had seen this originally but did not consider it as a fault indication, as ALL of these readings were an order of magnitude lower than Norcal715 showed. Among the readings in my set however, most of them being closer to 0.09, the 0.5 reading was close to 10 times (20db) higher. This had to be the one transformer of the defective lamp. I removed the transformer and replaced it with a jumper across the two outside pins on the solder pad, restarted the set without fault detection.

As Norcal715 showed in the video, with a solid color background, that's the only time the missing lamp is noticeable exactly as indicated in the video. Certainly no reason to create more electronic waste to which this one was headed when I was offered it for free. Thanks to all guys and gals, this is a maverlous forum!!

[vinceroger69]

Re: Samsung LNT4053H BL ISSUR

Thanks for the follow up regarding what fixed the tv nocal715 does some really good videos its a pity he hasnt made any recent ones in about 6 months as there very informative

[budm]

Re: Samsung LNT4053H BL ISSUR

The AC reading on the Anode side of the diode may show low reading on your meter because of the limited bandwidth of your AC Volt meter.
Best to test in DC mode on the Cathode side of the Diode with the meter that can do fast peak hold function.

[jkb242]

Re: Samsung LNT4053H BL ISSUR

Thanks for the follow up regarding what fixed the tv nocal715 does some really good videos its a pity he hasnt made any recent ones in about 6 months as there very informative

Indeed he is a very good illustrator and is a talented instructor obviously. Does he have a contact for PM's?

[jkb242]

Re: Samsung LNT4053H BL ISSUR

The AC reading on the Anode side of the diode may show low reading on your meter because of the limited bandwidth of your AC Volt meter.
Best to test in DC mode on the Cathode side of the Diode with the meter that can do fast peak hold function.

I have a Meterman that has a response up to 40Khz and it also has the sample hold feature. Measuring DC values I would not have been able to meter at the board test points since these are on these points cathode side. I found this an extremely interesting diagnostic approach for sets with a balance board design. Do you know if this is a design employed in current modles?

Looking forward to the next project that will soon be on the way to me.

[budm]

Re: Samsung LNT4053H BL ISSUR

To test the DC you need to test it at the center leg (Cathode) of the dual diode.
BTW, what is the model number of this Meterman?

[jkb242]

Re: Samsung LNT4053H BL ISSUR

To test or meter AC voltages Anode for DC voltages, I agree it's the Cathode.

Mine is a 33XR

Thanks my friend!