Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work).

[nomoresonys]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

I see, sometimes you end up with junk from ebay, but the buyer is always protected, at least for the part if not for return shipping.

[Xandros]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

Cynical me was wrong. They emailed me today saying they'd send a replacement and suggested I dispose of the damaged board rather than bother sending it back to them. I guess they'll be claiming compensation from UPS.

[Xandros]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

Got another board today. This time packaged much better! Worked too, TV is back to it's old self. So, there we have it.

[nomoresonys]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

Glad to hear it and nice to see they stood behind their product and did the right thing.

[saddle_au]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

Removed due to update.

[gladi15]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

Hi,
I have a similar problem with the same model..After the tv is on for 15mins..its start flashing depending on the content of the picture.if its too much alternating between dark and white lights it start flashing backlight.

The PSU is coded PSU - BN44-00340B no 00340A have changed the inverter the but the problem remains.can be a problem with CCFL or psu dont know which.

One way to go around is to keep alternating between pic modes until it goes steady again but the flashing come back and gets really annoying after a while..

Ron did you manged to get it fixed by replacing PSU or CCFL..??

[davidpringle]

Sure, here's the back of the tv, and minor close ups of both the boards. Camera isn't fantastic though so don't expect a marvel of photographic intensity though I can do a even closer close up if needs must of course. Also for what it's worth, here's the wiring diagram for the power board (the one linked in that thread doesn't work but I found it elsewhere).

hello, iv just inherited this set and have a spare board, however the capacitors have been removed. im replacing capacitors and im looking to know what value to use. please help

[tw2005]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

hello, iv just inherited this set and have a spare board, however the capacitors have been removed. im replacing capacitors and im looking to know what value to use. please help

A little vague. Photo, board number , part locations? all the CAPS?

[lospiratos]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

I have the same problem with this type of TV. Has anybody ever found which component causes this kind of issue?

[budm]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

I have the same problem with this type of TV. Has anybody ever found which component causes this kind of issue?

Does your TV use the same exact boards as the OP? OP got the TV fixed by replacing the power supply board to fix his issue.
Is your TV the same model as the OP?

[lospiratos]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

Yes, exactly the same boards and symptoms. I dont want to switch the board, but fix it instead. The circuit is available so I think it should be doable.

[nomoresonys]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

Start with test in post #8 if you didn't already.

[lospiratos]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

I already did that, then the backlight works perfectly fine. PFC voltage is 377V, is that enough?
To disable the protection circuit I've removed DI811. Now the backlight doesn't turn off anymore, but it flickers slightly.
Now I'm trying to debug the VSNS and ISNS lines, but it looks fine at first sight. It's a bit hard because I don't really know which signals to expect.
One thing that I've noticed is that the LD signal sometimes triggers, what's it's purpose?

[nomoresonys]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

That test verifies the backlights and powerboard, so if you are messing with the powerboard you are probably on the wrong trail.

[lospiratos]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

The PWM signal from the main board is also correct.
I think something goes wrong in the PFC circuit when the inverter starts to dim.

[budm]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

What is the PFC Voltage on the main filter caps when the backlights start flickering? <360VDC?
Does it flicker less if the backlights is turned down to 25%?
If you look at page 2 of schematic, there is low PFC Voltage detector circuit on the top left of the page, you can see ICP802, PCS804 and a bunch of resistor network. I expect the PFC Boosted Voltage to be around 390V typ.
LD = Lamp detect, it is Lamp error signal.

[nomoresonys]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

Conflicting information, "the backlight works fine, backlight doesn't turn off, backlight flickers"

[nomoresonys]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

Disabling protection is not exactly proper procedure.

[lospiratos]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

It allows to measure without the module shutting down after a few seconds. Those backlight states are all in different situations.
Without PWM the backlight works fine at highest brightness level, this lets me think that the lamps are fine. The flickering starts when the lamps need to dim with PWM. I also don't suspect the feedback signals anymore, because the A and B output on LX6503A is constant thus not causing the flickering.


How can I safely measure the PFC voltage with my scope?