Samsung LE40B652T4WXXU Screnn flicker now black screen

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

transformers have 4 connections on one side, 2 on the other
which ones do you want me to measure

[budm]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

See the diagram on page 2? Check pin 1 and 4.
BTW, any one of the 4 transformers looks burnt or have burnt smell?

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

transformers all look perfect with no signs of or smell of burning

[budm]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

Resistance readings of pin 1 & 4?

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

not sure if I am measuring correctly but not getting any reading between pin 1 and 4 on three transformers, on the 4th transformer am getting 0.32 between 1 and 4, if that makes sense to you

[budm]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

OK, I see why now, one of the transformer has pin 2 and Pin 3 linked together, the other 3 do not so on the other 3 transformer you will take the readings between 1 & 2, and 3 &4 instead.

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

all 4 transformers give the same reading of 1.6 between pins 1 & 2 and pins 3 &4

[budm]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

"on the 4th transformer am getting 0.32 between 1 and 4"
"all 4 transformers give the same reading of 1.6 between pins 1 & 2 and pins 3 &4"
1.6K? and only 3 have the same reading, right? if that is the case, then them seems to be OK.

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

yes that is right

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

do you know how to disable the protection on this power board, to force backlights to stay on to see if all backlight lamps are lit

[budm]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

I have to study the IC spec sheet I provided to figure that out.
Pin 2 looks to be shutdown timing cap, but I do not know if pin 5, 6, and 7 will still be able to kick in the protection or not. You can Ground pin 2 and see.

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

just grounded pin 2 tv has powered up and backlight is ON

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

looking very close at the screen lit I am convincing myself that there is one backlight lamp not lit, slight shadow across screen 3rd lamp up from the bottom of screen, I have never noticed it before and is hardly noticable

[budm]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

At this point we know the inverter circuit is probably OK, since the Inverter board has fingers for high Voltage that fit into the sockets where the ends of the lamps are, you may want to inspect the socket first before taking the panel apart to inspect the lamps, just be real careful, those fingers of the circuit board break real easy.

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

is it ok to remove the black plastic connector strip that the power/inverter board plugs into, I assume on the other side of this connector strip is where the backlight lamps are plugged into

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

anyone know where I can get a replacement ccfl tube prefer from uk, new or used, before I take the screen apart, I would rather have a spare tube ready if I need to replace one than take the screen apart then have to wait for a replacement to arrive.
I did find references on the net that it is known for these lamps sometimes to become disconnected and just need clipping back, however can not tell without taking screen apart

[budm]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

is it ok to remove the black plastic connector strip that the power/inverter board plugs into, I assume on the other side of this connector strip is where the backlight lamps are plugged into

No do not remove the connector, you will break the lamps.
Yes, it can be bad connection on the lamp socket.

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

yes just realised not to remove the connector, have sourced a replacement lamp from a local tv repair company will take it apart and replace the lamp as soon as I get the replacement

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

FIXED FIXED
changed 3 lamps in total. one not working at all, black at ends as in picture, another two going black but working so changed them as well, put back together all seems well up to now, and no flickering, Up to now good job well done another tv saved from landfill.
tv shop charged me £5 for 6 lamps

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

Thanks again for all your help