The infamous 2 seconds to black

[vokwok]

Re: The infamous 2 seconds to black

yes led stays on.
and yes i did use low ESR caps
and yes i did measure transformer's both sides and it did match. both was very near 1kOhm
i did check solder joints and now i need to change CCFL to working one's.

[PlainBill]

Re: The infamous 2 seconds to black

area you saying CCFL are broken or even one of them is broken ?
what is easyest way to test these CCFL ?
should the monitor stay on if i dont connect CCFL connector's to board?

First, let's verify one thing. When you turn on the monitor you get a display for about two seconds, then the display goes blank, but the power LED stays green? That is two seconds to black, which has several possible causes.

You have replaced the caps. Did you use low ESR caps?

You have measured the transformers. Did they match to within 3%?

The next likely cause is a bad CCFL, or wiring to the CCFLs. Some monitors are notorious for bad solder joints at the CCFLS, or frayed wiring. A broken CCFL is also possible. The easiest way to test that is to substitute a set of known good CCFLs. They don't have to be installed in the LCD panel, I use a pair that are in the reflective channel.

The last possible cause is a defective component in the protection circuitry; testing that is very difficult.

PlainBill

[vokwok]

Re: The infamous 2 seconds to black

area you saying CCFL are broken or even one of them is broken ?
what is easyest way to test these CCFL ?
should the monitor stay on if i dont connect CCFL connector's to board?

[PlainBill]

Re: The infamous 2 seconds to black

I have Fujitsu siemens monitor with same guts like this acer
and problem is also 2 seconds to death.
when monitor is turned on there will be very good picture from computer for 2 secs and then it goes blank. I have replaced all caps and i did measure the transformer and fuses too. could someone give me a hint what to look next?
and i did use vga and dvi input and there are no diffrence between them.

Substitute known good CCFLs.

PlainBill

[vokwok]

Re: The infamous 2 seconds to black

I have Fujitsu siemens monitor with same guts like this acer
and problem is also 2 seconds to death.
when monitor is turned on there will be very good picture from computer for 2 secs and then it goes blank. I have replaced all caps and i did measure the transformer and fuses too. could someone give me a hint what to look next?
and i did use vga and dvi input and there are no diffrence between them.

[attrib]

Re: The infamous 2 seconds to black

Re: The infamous 2 seconds to black

I want t say that My Acer AL2223W had the same problem and it WAS he transformer ( SPI 8TC00332 ) So I just had a old used ACER monitor with scratched screen and it that had a transformer ( SPI 8TC00245 ) inside. So i used that one to replace my transformer that had a 2.5K ohms on one side and a 1K ohms on the the side side.. Both sides should have no more ten 1K ohms reading on both secondary windings.

If you need a new transformer or SUB replacement. you can also use ( MS220T )

Check here
http://www.lcdparts.net/TransformerD...ProductID=2796

Anyway as long as the transformer has the same readings it should work proper. I just did this fix today.. it was perfect...

Oh one more thing.. Remember to have a signal going to the monitor from your computer.... This way the lights of the screen will stay on... otherwise it will time out.

TAKE CARE ALL
Cheers from Canada...


THE END

[MegaOne302]

Re: The infamous 2 seconds to black

From my very limited knowledge, 3 main things that go bad. 1 a CCFL tube, you'll see black ends. 2 a bad cap, they're usually bulging. 3 a bad Scotty diode, these guys turn gray or start cracking.

Oh ya, let's not forget a blown fuse.

[shimjocky]

Re: The infamous 2 seconds to black

Thanks for the lesson, much appreciated.

[PlainBill]

Re: The infamous 2 seconds to black

Thanks PlainBill. I will get the new one on order asap.

If you don't mind a follow up question regarding the transformer I would like to ask if one secondary is bad can it keep the other side from working as well?

When I got these readings I kind of thought that the lights powered by the good side of the transformer should work. Granted it was an uneducated assumption, just curious.

It depends on the design of the transformer and the inverter itself, but usually, a failure affecting one tube will shut down the entire backlight system.

A brief summary of what happens when an LCD monitor is turned on. The logic card sends a signal to the inverter controller to turn on the CCFLs. The inverter controller turns on the CCFLs at full power. A fraction of a second later it begins checking the voltage across and current through each CCFL. If any are out of spec, the inverter controller shuts everything down - two seconds to black.

NOW, some designs do not check both current and voltage. Or they may do only a partial check - shut down only if the voltage across a CCFL gets too high. And some (those inverters used in case lights don't check anything!

PlainBill

[shimjocky]

Re: The infamous 2 seconds to black

Thanks PlainBill. I will get the new one on order asap.

If you don't mind a follow up question regarding the transformer I would like to ask if one secondary is bad can it keep the other side from working as well?

When I got these readings I kind of thought that the lights powered by the good side of the transformer should work. Granted it was an uneducated assumption, just curious.

[PlainBill]

Re: The infamous 2 seconds to black

Got the transformer off and the readings are the same as before.

That is definitely a problem. Usually the secondaries will match to within 1% or so. A 10% difference is a sure sign of problems. You have a 4:1 ratio.

Replace it.

PlainBill

[shimjocky]

Re: The infamous 2 seconds to black

Got the transformer off and the readings are the same as before.

[shimjocky]

Re: The infamous 2 seconds to black

Yep, looks like I did most of the same checks. I am going to remove the transformer so I can get good readings on the primary as well.

I am curious if the deviation in the secondary readings is acceptable.

[retiredcaps]

Re: The infamous 2 seconds to black

I found these 2 videos very useful to test the transformers (about 10 minutes in total). Sounds like you followed this same procedure.

http://www.youtube.com/watch?v=eNuGWBPRGKA

http://www.youtube.com/watch?v=IQkSu0JBTTU

Since I am looking at the transformer I decided to read up on it a bit. I found a website that sells them, and they also list the specs. They say the primary should have about 0.3 ohms and the secondary about 1.0k.

I got the following.
P1-P2= 0.5
P3-P4=0.5
S1-S2=3.95 K
S3-S4=1.01 K

I did this check with the transformer on the board.

[shimjocky]

Re: The infamous 2 seconds to black

Since I am looking at the transformer I decided to read up on it a bit. I found a website that sells them, and they also list the specs. They say the primary should have about 0.3 ohms and the secondary about 1.0k.

I got the following.
P1-P2= 0.5
P3-P4=0.5
S1-S2=3.95 K
S3-S4=1.01 K

I did this check with the transformer on the board.

[shimjocky]

Re: The infamous 2 seconds to black

I kind of thought that might be the case. Thanks for verifying.

Since they all light up in a similar manner I am inclined to think that the bulbs might be ok. I started looking over the psu/inverter again hoping something would jump out at me. I saw what looked light a hairline crack in what I think is the high voltage transformer. I cleaned it up with alcohol to make sure it wasn't just dirt, but its still there. I don't know much about these little guys, but I thought it might be worth mentioning. You can easily see what I am referring to in the pic.

Can transformers contribute to the symptoms I have, or do they tend to fail totally and suddenly?

[EGuevarae]

Re: The infamous 2 seconds to black

does my inverter not have enough power to light them up?

[shimjocky]

Re: The infamous 2 seconds to black

Howdy folks.
Sorry it's been so long since my last posting. I have been really busy trying to keep up with the ol college schedule.

I recently acquired a small inverter (used for a ring light that was on a fan) and tested each of the 4 bulbs individually. All 4 bulbs would light up a bit short of half way down from the side where the wires go in, and just a bit from the other end. They leave a big dead area in the middle and the light starts off white and peters off to a purple color the closer to the middle of the bulb you get.

Is this a sign of bad bulbs, or does my inverter not have enough power to light them up?

[EGuevarae]

Re: The infamous 2 seconds to black

To those who have been helping I am still working on getting the stuff to test my back lights. Looking forward to seeing this puppy work again. Thanks again for your troubleshooting expertise.

OK,good. Post any result you get.

[shimjocky]

Re: The infamous 2 seconds to black

To those who have been helping I am still working on getting the stuff to test my back lights. Looking forward to seeing this puppy work again. Thanks again for your troubleshooting expertise.