LN40C540F2F 6 blins then dead unit

[kgavionics]

Hi i have a samsung LN40C540F2F i want to fix.when i put the power plug the red light flashes 6 times stops and remain like that.
i took the unit apart and measured the voltages ( see picture)
the powerboard seems to be good according to the voltages and no bulging caps.
the backlight is working fine if i unplug the connector between the PSU and the mainboard ( saw this trick online with this particular set)
i suspected the mainboard not sending the PS_ON voltage (0.9V), but i have read a post here in this forum a guy had 0.8V and the tv was working fine.
i'm leaning toward the mainboard, but i would like to have your input please
thanks in advance

[attainteddragon]

Re: LN40C540F2F 6 blins then dead unit

your ps-on is most likely good. some of these newer sets only need around .8v

you are missing your back light on signal though, so your issue will be main board.

[kgavionics]

Re: LN40C540F2F 6 blins then dead unit

your ps-on is most likely good. some of these newer sets only need around .8v

you are missing your back light on signal though, so your issue will be main board.

thanks attainteddragon
when i remove the connector between the mainboad and the PSU i get the backlight and the pin BLU_ON is pulled high (5V).
i'm planning to fix the mainboard, because i have fixed a few of them on the past.Hopefully, the problem is not coming from a chip, otherwise it's fixable.

[attainteddragon]

Re: LN40C540F2F 6 blins then dead unit

mainboards are never fun. i look forward to seeing how you go.

[kgavionics]

Re: LN40C540F2F 6 blins then dead unit

mainboards are never fun. i look forward to seeing how you go.

Yeah! you're right!!!wish me good luck

[kgavionics]

Re: LN40C540F2F 6 blins then dead unit

i'm looking for the schematic of the main board, but i can find it.the serivice manual i have doesn't have any schematics of any board.can someone help me to find a service manual including the schematic of the mainboard?
thanks in advance

[dskall]

Re: LN40C540F2F 6 blins then dead unit

Not likely you going to find schematic for main board. Most service manuals now are rebadged owner manuals. Manufactures don't want their tv's to be repaired

[kgavionics]

Re: LN40C540F2F 6 blins then dead unit

Not likely you going to find schematic for main board. Most service manuals now are rebadged owner manuals. Manufactures don't want their tv's to be repaired

The best service manuals i came across are Sharp , panasonic and sony, they are so detailed and the schematics are well drawn.The Samsung service manual have is crap in my humble opinion.In their troubleshooting flow chart, i didn't find any case of 6 blinks.Knowing this will help me finding out if the problem is coming from a chip or just a simple component.

[dskall]

Re: LN40C540F2F 6 blins then dead unit

While monitoring ps-on and pushing power button you get no change

[kgavionics]

Re: LN40C540F2F 6 blins then dead unit

While monitoring ps-on and pushing power button you get no change

PS_ON remains 0.9V no change.
i checked the mainboard with my oscilloscope and i can't see any activity ( no wave forms),the only wave form i have is the crystall sine wave of 24 MHZ.so either the maincircuit is not working ( it's a BGA chip maybe a reflow can solve the problem) or it's not biased corrctely due to a bad component ( voltage regulator , diode, transistor..)

[dskall]

Re: LN40C540F2F 6 blins then dead unit

And you get your various main voltages

[kgavionics]

Re: LN40C540F2F 6 blins then dead unit

And you get your various main voltages

the voltage on the regulator seems right, but i'm not quite sure,because without schemtic hard to tell if it's right or wrong.

[dskall]

Re: LN40C540F2F 6 blins then dead unit

Common main board voltages: 1.1v, 1.8v 3.3v 5v 9v 12v 15v
Should be a number of voltages to check

[kgavionics]

Re: LN40C540F2F 6 blins then dead unit

Common main board voltages: 1.1v, 1.8v 3.3v 5v 9v 12v 15v
Should be a number of voltages to check

i've measured 1.8V,3.3V,5v and 12V,but never came across 1.1V,9v and 15V.i'll test again and report back.

[dskall]

Re: LN40C540F2F 6 blins then dead unit

Those are just common voltages. Not specific to all. Unfortunately one size does not fit all. If you found a 4v or 7v or .8v etc. those would be uncommon and suspicious

[kgavionics]

Re: LN40C540F2F 6 blins then dead unit

I tested pretty much all the semiconductors and they seems alright.
So, i went and heated the mainboard for 1min on the oven and guess what,the tv worked on time only.grrrr!!!!