Samsung 40" LCD tv model LN40B610A5FXZA won't turn on

[imaddicted2u]

Samsung 40" LCD tv model LN40B610A5FXZA
It's been acting up for a while and has gradually gotten worse. I think it might be caused by bad power supply caps but none visibly look bad. It started working for a day, then reverted to the problem state.
I'll describe the symptoms:
Was working, it shut itself off, red standby led is lit, won't respond to power on from front panel or remote. When unplug/plugged back in it will sometimes have the standby led lit, other times the led is not lit, sometimes it will start up, show a display for a few seconds, then shut off. Two days ago it worked for the whole day, next morning, it turned on but in the evening the set would not turn on and hasn't since.
I know I have to check the stand by voltage to start with but I'm open to other suggestions of things to check.
I have another question, I'm gathering up some caps in case I have to replace any on the board. On the power board, there are 2 X 82MFD at 450volts in parallel. I have 2 X 100MFD at 450volts from a Samsung Series 5 LCD TV. Do you think using the 100s would hurt anything?

[imaddicted2u]

Re: Samsung 40" LCD tv model LN40B610A5FXZA won't turn on

Sorry for double post.

[neilc6]

Re: Samsung 40" LCD tv model LN40B610A5FXZA won't turn on

Think this model suffers from a burnt transformer on the inverter section. Second from bottom, will have a burnt spot. Pictures would confirm including whole back of the tv and that section.

[imaddicted2u]

Re: Samsung 40" LCD tv model LN40B610A5FXZA won't turn on

Thanks, It's my sister's TV. I have to pick it up later today, when it worked for a day I took it back to her, hooked it up and it worked. She came home turned it on and the display showed but it turned off after a few seconds. When I had it here, I looked the board over top and bottom, didn't notice anything burnt but will look closer and post pics when I get it apart again.

[Unspun01]

Re: Samsung 40" LCD tv model LN40B610A5FXZA won't turn on

Think this model suffers from a burnt transformer on the inverter section.

Neilc6 is correct. A common failure of these power supply/inverter boards is the blue or white inverter transformers.

Check all of the blue and white inverter transformers for burns or discoloration on the plastic wrap. If you look hard, you may spot whitish evidence of arcing beneath the yellow kapton tape.

Inspecting the bottom of the board below each inverter transformer may show discoloration of the PCB board that will tell you which transformer was running hot.

You may have to replace more than one transformer. On one board I repaired, I had to replace 3 transformers: two white ones and a blue one.

If the TV is working briefly, you may feel for high temperature with your fingers but be careful.

The part number are:
White: QGAH02095
Blue: QGAH02098

See the attached image for information.

The parts can be ordered from Shopjimmy.com or on ebay. Relatively easy repair with decent tools.

[imaddicted2u]

Re: Samsung 40" LCD tv model LN40B610A5FXZA won't turn on

Ok, thanks for the replies. I brought it home. Plugged it in, only had red standby led. Took the back off. Tapped around the power board. Plugged it in...got blinking red led. it booted. I put a signal to it and the pic appeared for about 5 minutes, went black, no red led. Cycled the power, only have a solid red led now. STBY measures 5.15v and PWR-ON/OFF measures 0.878v. CP815 and CP816 have 370-400v on them. My BN44-00264A board has 4 black transformers. Can't see any signs of burning, arcing or heating. No caps look bulged. I re-soldered the connections for the transformers and the ribbon cable connector anyway. No change.
Some pics:
Back of set

Power/inverter board-top

Power/inverter board-bottom

Power/inverter board-Top side-bottom

Power/inverter board-Top side-top

Power/inverter board-Bottom side-bottom

Power/inverter board-Bottom side-top

Logic board-top

Transformer-2nd from bottom-top

Transformer-2nd from bottom-bottom

[Unspun01]

Re: Samsung 40" LCD tv model LN40B610A5FXZA won't turn on

ok, it looks like you have the more reliable power supply of the two kinds. You may want to test the high voltage side resistances (on the 4 pin side, between pins 1-2, and 3-4). See if they are all approximately the same as one another. If one measures quite differently it could be bad. Otherwise I have not really seen those inverter transformers go bad.

By the fact that your TV works, but intermittently, I suspect you have cold-colder connections somewhere. RE-check all of the connector pins and any transistors or diodes that are attached to a heat sing, and any large diodes or fusible resistors that may get hot and re-solder them all...

[budm]

Re: Samsung 40" LCD tv model LN40B610A5FXZA won't turn on

So what do have for the BL-ON and dim control signal when the backlights are not on?

[imaddicted2u]

Re: Samsung 40" LCD tv model LN40B610A5FXZA won't turn on

You are right Unspun01. I think I found it. See inside the circle in the pic...zoom in, you can see it. It is actually one end of one of the heat sinks next to the high voltage caps. I was re-soldering all the heavier solder joints on transformers and other components. I felt something click when I picked up the board. I twisted it a bit and tracked the clicking down. I'm glad I felt it. I was in the process of soldering the pads for all the heat sinks and it would have started working but I would not have known why. Working fine...so far...so good.

[tvtimmy]

Re: Samsung 40" LCD tv model LN40B610A5FXZA won't turn on

Whenever I get one of these types of power supplies, the first thing I do is gently flex the board and listen for the "click ". Then check the fuse, mosfets,diodes............

[cdoublejj]

Re: Samsung 40" LCD tv model LN40B610A5FXZA won't turn on

i too LN40B610A5FXZA, it turns off but, it either flickers and shuts off OR it shuts after a few minutes, the colder it is the better. when on white static screen i see a tinge of red towards the bottom of the screen but, on HDMI hooked to a computer the picture looks good. i was thinking bulbs. going to look at the inverter board.

trying to see with the limited 1 or 2 minutes if this unit eve has decent black levels, if no it's not worth really saving but, if the black levels are ok then its probably BETTER than half the TVs at this size new for $170 to $290

EDIT: well it wasn't a cold solder joint. i threw a shop jimmy kit at this thing a year ago that didn't make any change either. it replaced some caps, and IC and transistors. the the PCB is no better for the wear as i had the iron turned up but, im thinking that's not it either since it didn't really change in behavior.

the red tinge only goes away after it's warmed. up touching up a bunch of joints it's flickering less.




btw black levels seem to be a little better than my $160 bestbuy insgina 43" TV. However i've also been spoiled by CRT and OLED black levels too.

https://www.shopjimmy.com/samsung-bn...repair-kit.htm

Still has a slight red tinge after warming up.

EDIT: reaplced the 1000uf 10v and 1000uf 25v lytic caps and flicker is reduced but , looks it's coming back as it's warming up