Samsung le40n71b goes black after 2 sec

[nalle077]

Re: Samsung le40n71b goes black after 2 sec

i have tested with the lamp and number five from the bottom looks a little darker.
I took a photo in the dark and there it is visible to just before it shuts down the light.
I will try the dc test tomorrow.

Edit: Number 5 from the right. The photo became wrong way.

up

[budm]

Re: Samsung le40n71b goes black after 2 sec

Once you test the DC output from the Diodes, then you may try reseating the lamps, it looks like the lamps are socketed in place.

[nalle077]

Re: Samsung le40n71b goes black after 2 sec

Once you test the DC output from the Diodes, then you may try reseating the lamps, it looks like the lamps are socketed in place.

Have tested with dc now.
red probe on single point like arrow in photo.
black probe on gnd.
about 7.35 volt on every diod
It does not look the same on my set like in the video.
If I want to try the AC test.
Is that possible and where to set the probes than?
You mean reseat the tube?
Disassamble everything like in video number 2?????
Cant I do the jumperthing like he does?
It seems like I do not have a transformer for every tube like he did?
Or is it one transformer for 2 tubes in my case?

[budm]

Re: Samsung le40n71b goes black after 2 sec

Those are the correct Diode, I expect the one with bad lamp will show higher reading than the rest.
I really do not like to have you take the panel completely apart to get to the lamp due to more chance of breaking the lamp or the screen.
Not sure abut the jumping the transformer, I need to look at the pictures of the board that I download to see how they are connected first.

[nalle077]

Re: Samsung le40n71b goes black after 2 sec

Those are the correct Diode, I expect the one with bad lamp will show higher reading than the rest.
I really do not like to have you take the panel completely apart to get to the lamp due to more chance of breaking the lamp or the screen.
Not sure abut the jumping the transformer, I need to look at the pictures of the board that I download to see how they are connected first.

I could not see any difference in the reading of any diode. All went up to 7.35V before shutting off.
But do you think that a bad seated tube is the problem.
is 7.35 ok. In the video he had much less I believe.
Is it like one transformer is for 2 tubes in my set?

[budm]

Re: Samsung le40n71b goes black after 2 sec

Since it is not the exact same design, the Voltage level may not be the same, but since we are looking the Delta of the Voltage to see if any one of them shows differently but we are not seeing it. The Voltage at LD pin is the errors signal and normally should be >11VDC, <10V = error. I need to study more to see what is going on, may be I can find training manual for this series.

[nalle077]

Re: Samsung le40n71b goes black after 2 sec

Since it is not the exact same design, the Voltage level may not be the same, but since we are looking the Delta of the Voltage to see if any one of them shows differently but we are not seeing it. The Voltage at LD pin is the errors signal and normally should be >11VDC, <10V = error. I need to study more to see what is going on, may be I can find training manual for this series.

ok thanks for your help so far.

[budm]

Re: Samsung le40n71b goes black after 2 sec

1) Can I get really clear straight shot of the this connector to see where LD pin connection goes to?

2) Please put the DCV meter on the LD pin and see when power switch is activated it is at 12VDC and then see if it drops down when the backlghts go off.

[nalle077]

Re: Samsung le40n71b goes black after 2 sec

1) Can I get really clear straight shot of the this connector to see where LD pin connection goes to?

2) Please put the DCV meter on the LD pin and see when power switch is activated it is at 12VDC and then see if it drops down when the backlghts go off.

The reading on LD pin is 6.5V when I turn on the set. When the backlight lid it goes to 0V for 0.5 seconds then goes back to 6.5V when the backlight fail.
did not see that when I did reading earlier. Sorry.

[budm]

Re: Samsung le40n71b goes black after 2 sec

"The reading on LD pin is 6.5V when I turn on the set. When the backlight lid it goes to 0V for 0.5 seconds then goes back to 6.5V when the backlight fail." OK, that does not sound right, but you do have 13V on that connector, right?

[nalle077]

Re: Samsung le40n71b goes black after 2 sec

"The reading on LD pin is 6.5V when I turn on the set. When the backlight lid it goes to 0V for 0.5 seconds then goes back to 6.5V when the backlight fail." OK, that does not sound right, but you do have 13V on that connector, right?

Do you mean when the set is in standby?
I think it was about 0,8V on standby on the LD-pin with the connector connected

[budm]

Re: Samsung le40n71b goes black after 2 sec

When TV is turned on. There is a 13V pin on that connector. The LD signal is generated by the comparator circuit that either at >11V (GOOD) or <1V (LAMP ERROR).

[nalle077]

Re: Samsung le40n71b goes black after 2 sec

When TV is turned on. There is a 13V pin on that connector. The LD signal is generated by the comparator circuit that either at >11V (GOOD) or <1V (LAMP ERROR).

Yepp 14,5V on that pin. 13.5V the little time when backlight was on

[budm]

Re: Samsung le40n71b goes black after 2 sec

I have look and see if I have that spare balancer board some where.

[RJARRRPCGP]

Re: Samsung le40n71b goes black after 2 sec

Hello friends. I have a samsung le40n71b that goes black after 2 sec.

Probably a bad CCFL, a bad CCFL connection or a faulty inverter transformer.

May just need resoldering.

[nalle077]

Re: Samsung le40n71b goes black after 2 sec

Probably a bad CCFL, a bad CCFL connection or a faulty inverter transformer.

May just need resoldering.

how to know which part is bad?

[nalle077]

Re: Samsung le40n71b goes black after 2 sec

how to know which part is bad?

Up

[budm]

Re: Samsung le40n71b goes black after 2 sec

BTW, you may want to read this while I do more research, see page 45.
We may be able to fool the LD pin for testing purpose.

[nalle077]

Re: Samsung le40n71b goes black after 2 sec

BTW, you may want to read this while I do more research, see page 45.
We may be able to fool the LD pin for testing purpose.

Very interesting.
Yes I can try to put a jumper between 13V and LD ? not as final sollution of course, just to test if it stays on.
Do you think anything else will break ?
Note also that I have a Samsung and this training manual is for SONY.
But I guess it works the same?
Is there a training manual like this for Samsung perhaps?

[budm]

Re: Samsung le40n71b goes black after 2 sec

You have to remove the LD wiree from the inverter board connector first and then use 1K resistor between the 13V and the LD wire that you just remove from the connector.
SONY and SAMSUNG were working together on the TV design. You will see SONY/SAMSUNG 'S' I forget the name of the two companies use. I look for SAMSUNG Training but did not find the one for this chassis.