A guide on how to troubleshoot 2 seconds to black

[stevwills]

Originally Posted by stevwills

the both lamps don't turn completely on. they kinda turn on like a loading screen. (they both go at the same pace.) and before they hit the end, the monitor turns off.

when is say the monitor turns off, i mean only the panel. the speakers and the power led stayes on.

[mikail13]

SAMSUNG P2270HD
2 Second to black

other parts are O.K. ie. CCFL.
this power board kills my life...

everthings seems O.K.
i.e. caps. i test them on board.

any idea?

[budm]

You should make a thread regarding to your monitor, this thread is for the guide only, not for any particular model.

[mikail13]

i get it. it can delete. how can i move the post and pics?

i re-upload pics on new thread..

please delete my last two post on there..

[b19_george]

Hello, I have an Benq ET-005-N with backlight problems, the CCFL lamps are not starting at all but i test them and are fine, I know the monitor works because I used another board to fire up the CCFL lamps and once the lamps are on you can see the image on the screen, the caps are replaced are not bulging and tested for capacitance, the transformers have the same resistence both of them (0.63K) so either are both damaged or is the right reading. Any advice will be more than helpfull!

[cmg]

I have two identical 27” LED monitors to fix. Both of these seem have this “2s to black” type problem where they seem to power up, an image flashes briefly then they go back to standby.

I have a lot of experience in fault finding circuits but not with LED Monitors/TVs. Before I get going I’d like to ask some general advice.

Specifically I’d like to get some advice on how to test the PSU isolated from the logic boards. I can see that there are various fault conditions where the power is shutdown deliberately by protection circuitry – for instance going into standby when there is no signal, shutting down then the backlights are faulty etc. I’d like to know how to test the PSUs in LED monitors/TVs with the logic circuity and screen unplugged so that I can check the PSU itself first. As far as I can tell, if the PSU is simply unplugged from the logic circuits, it would remain shutdown like a PC’s ATX PSU does, so couldn't be tested without some test circuitry.

There are two reasons I want to approach it this way:
1) I want to isolate the problem. For this type of issue where the appliance seems “dead” it is logical to test the power supply first, and
2) These devices are clearly very dangerous to run live. I do have experience working with high voltage circuits (upto 1kV). The best advice for these is to avoid live diagnosis of the HT areas as much as possible. These circuits could be deadly. Having a methodical way of testing these would make the process safer.

I guess the advice to do this would apply to many monitors. The monitors I have are HP ZR2740W. I can't find the circuit diagrams for these so I can’t work out the answer to this easily myself. I’ll start a new thread for these monitors but if there is general advice perhaps it is best for people to find here.

Thanks in advance!

[_MsG_]

Don't wanna hijack anything here in the topic, but I'm wondering how likely it is to have a bad high voltage cap. I have a topic here: https://www.badcaps.net/forum/showthread.php?t=66726

I'ts a bout a LG monitor with CCFL backlights, and the backlight goes off after ~ 3 seconds, while the image and everything stays perfectly on (of course only visible with a flashlight). I already replaced the regular caps, but it didn't change anything. So I was thinking about replacing the big capacitor (120µF 450V). However in the Cap kits you can buy for monitors I never see the big capacitor being in the kit, nor did I see anything here in the troubleshoot topic mentioning the big cap.

Is this thing likely to fail, or is that very rarely the case?

[ronie1981]

Very useful thread, thank you for sharing...