Samsung 40inch lcd tv backlight goes off sound good

[shelby5041]

Re: Samsung 40inch lcd tv backlight goes off sound good

well if the sensor is shutting off inverter circuit then when i check bl=on pin i should get zero volt reading...that will be the key in this troubleshooting i think is the bl-on status when backlight goes off

[budm]

Re: Samsung 40inch lcd tv backlight goes off sound good

just noticed, this is the exact model Im working on.

I forget what your TV is not doing.

[budm]

Re: Samsung 40inch lcd tv backlight goes off sound good

well if the sensor is shutting off inverter circuit then when i check bl=on pin i should get zero volt reading...that will be the key in this troubleshooting i think is the bl-on status when backlight goes off

The error signal is not fed back to the main board to shutdown the BL_ON, it shuts down the inverter circuits and BL_ON will still be present if the error occurs.
The TV would have gone into standby or shutdown if the error signal is used by the main board.

[shelby5041]

Re: Samsung 40inch lcd tv backlight goes off sound good

oh ...

the backlight goes off randomly after powering tv on.....5 min 15 min 1 hr 2 hrs etc

i can watch tv fine good picture good sound etc etc...but then backlight goes off at random time..........if i wait 10 min and power tv back on it is fine again until a random time

.....so far when i power the tv on after not using for a while the tv always powers on with backlight working.......its just that after tv is on for random time the backlights will go out

[shelby5041]

Re: Samsung 40inch lcd tv backlight goes off sound good

ok so bl-on can still be present ...if the sensor senses a bad lamp and shuts down inverter curcuit.....ill check voltages on the other ps to main output when i get home.......when bl on and when bl off

[budm]

Re: Samsung 40inch lcd tv backlight goes off sound good

oh ...

the backlight goes off randomly after powering tv on.....5 min 15 min 1 hr 2 hrs etc

i can watch tv fine good picture good sound etc etc...but then backlight goes off at random time..........if i wait 10 min and power tv back on it is fine again until a random time

.....so far when i power the tv on after not using for a while the tv always powers on with backlight working.......its just that after tv is on for random time the backlights will go out

That what makes it hard, you have to be ready to make some measurement when it goes out.

[shelby5041]

Re: Samsung 40inch lcd tv backlight goes off sound good

if i had to make a guess without doing anymore troubleshooting i would guess the issue is in the transformer area.......seems to be a time/heat issue

but thats just my novice guess...i dont think its a bad lamp causing it since its intermittent.........a bad lamp would trigger fault all the time same time i would think,....and since i have good voltages i dont think its bad caps....

[shelby5041]

Re: Samsung 40inch lcd tv backlight goes off sound good

right now i have the tv taken aprt at home laying on table so i will power it on like that take voltages on all the pins then when it goes off ill take readings again

[shelby5041]

Re: Samsung 40inch lcd tv backlight goes off sound good

but i dont get home until 8a eastern time ...so until then have a good night and thank you very much i learned alot so far.......good thing about this is .i can get this power supply and main board cheap on ebay less than $30.00 .....cheap fix.....im just hoping its not a lamp issue.....

[budm]

Re: Samsung 40inch lcd tv backlight goes off sound good

You should do real good visual inspection on the board and touch up any suspect looking joints. You cannot make it go out if you poke around with plastic stick?

[shelby5041]

Re: Samsung 40inch lcd tv backlight goes off sound good

another thing i was thinking it it could be is a cap thats starting to go bad.....even though it looks good.....hence intermittent.....i have seen this before....

[shelby5041]

Re: Samsung 40inch lcd tv backlight goes off sound good

havent tried.....the guy on you tube would tap on the trans and the backlgiht would go on and off bad solder.....its a good video

[shelby5041]

Re: Samsung 40inch lcd tv backlight goes off sound good

here is the link to video https://www.youtube.com/watch?v=XdsDxKkcesg

[budm]

Re: Samsung 40inch lcd tv backlight goes off sound good

This board uses those eyelets for large component legs like the transformer. So look real close or just resolder all the pins on the transformer and those legs of the components mounted to the heatsink.

https://www.badcaps.net/forum/attach...2&d=1422648922

[nomoresonys]

Re: Samsung 40inch lcd tv backlight goes off sound good

I forget what your TV is not doing.

mine is just a snowy screen, can't see menu, pretty sure its the mainboard, just can't seem to track it down to component.

[nomoresonys]

Re: Samsung 40inch lcd tv backlight goes off sound good

was wondering if it was the c102, like you fixed on yours, but its not screeching or going on and off?

[shelby5041]

Re: Samsung 40inch lcd tv backlight goes off sound good

i may have found the problem as youtube video showed

under transformer is a severe cracked solder joint....im going to solder and let u know of it fixes.....its same joint as youtube video i posted...common issue with this model.....i kind of fogured this would be it sonce the way tv acted..i hope it fixes it

[shelby5041]

Re: Samsung 40inch lcd tv backlight goes off sound good

here is a pic of a bad solder joint of some sort..not sure if its critical or just a support joint for housing but its the exact same joint as inthe youtube video i posted prior that someone had exact same problem im having so hopefully resoldering it will fix it

i bought the tv for 10.00 from a guy who said pic would go out now and then..i used the tv for about 3 months and picture wouldnt go out like he said....but now it does and im hoping this will fix it...it would be a zero cost fix which are the kind i love

[shelby5041]

Re: Samsung 40inch lcd tv backlight goes off sound good

i was going to work on resoldering it today but had snow blower issues i had to deal with...we are getting 1 foot of snow tonight so i had to make sure i was ready...tv repair will have to wait.......i brought board to work and will resolder it here and will test when i get home tomorrow

[budm]

Re: Samsung 40inch lcd tv backlight goes off sound good

When you do the rework on the board, make sure to use flux.