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Old 04-14-2012, 08:52 AM   #1
smalltownguy
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Default Dell E228WFPC goes dim after 10 minutes, not 2 seconds

Working on a Dell 22" monitor I purchased from eBay. The monitor stays on for approximately 10 minutes, then goes dim. When it does go dim, cycling the power causes 2 seconds to black behavior. Leave the monitor powered off for a few hours repeats the ability to have it run for 10 minutes, then the issue reappears.

I've checked all the caps on the inverter board (Elite brand) with my blue ESR meter and all of them spec out fine.

I metered the blue caps near the transformers and got similar ohms between the two (secondaries, right?)

I DO have a few spares at work to check for possible CCFL failure, but I really don't want to pull apart another 22" panel that's in constant use unless I absolutely have to. These things are heavy and awkward.

My symptoms are similar to the ones described in this thread:

http://www.badcaps.net/forum/showthr...light=e228wfpc

And, of course, pics:
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Old 04-14-2012, 09:04 AM   #2
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

Just read your problem and the other thread. That's a strange problem.

Its a shame you don't have some spare ccfls to eliminate that. I can't help but think that heat is causing the issue. You could try to leave the monitor off for sometime then slowly heat up an area of the board to see if that bring the symptoms on earlier. This could help determined where the issue might be for you.
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Old 04-14-2012, 09:27 AM   #3
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

Sounds like a heat problem/ bad solder joint. Since you have 10 minutes before the problem occurs, may I suggest you try a hair dryer and heat up various portions of the power and logic boards to see if you can accelerate the problem. Hopefully, you'll be able to narrow down the board/area that's giving you the problem.
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Old 04-14-2012, 09:32 AM   #4
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

have you also checked the esr on the caps between the 2 heatsinks top right of picture?
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Old 04-14-2012, 09:37 AM   #5
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

Quote:
Originally Posted by vinceroger69 View Post
have you also checked the esr on the caps between the 2 heatsinks top right of picture?
Yes.

Before I try any hair dryer tactics, it would probably be a better idea to place my panel on the boards of a known working donor monitor. If the problem migrates, then I know it's a CCFL issue.
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Old 04-14-2012, 09:42 AM   #6
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

You don't have to heat anything up to the extent that u might damage anything just enough yo replicate the fault which normally takes a few minutes.
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Old 04-14-2012, 10:53 AM   #7
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

Hi if your boards are the same there is a longish thread here:
http://en.community.dell.com/support...px?PageIndex=1

Initially they thought it was a heat problem on the pwm though replacment did not seem to fix. They then added an extra resistor which appeared to work for some but for others was only partial fix as part of screen remained dim. I dont think they bottomed out why the resistor helped but of you were to extract all the relevant bits and could find a schematic for your your board i am sure budm would figure it out. If you could find a voltage regulator that should keep the voltage down to around 2v that is not working then that might be the answer

Does it stay on longer if you turn the brightness down?
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Old 04-14-2012, 11:31 AM   #8
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

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Does it stay on longer if you turn the brightness down?
Hm....I'll have to try that.
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Old 04-14-2012, 04:18 PM   #9
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

Quote:
Originally Posted by smalltownguy View Post
Hm....I'll have to try that.
Or try the converse. Pump the brightness and contrast to max.
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Old 04-14-2012, 04:29 PM   #10
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

"Before I try any hair dryer tactics, it would probably be a better idea to place my panel on the boards of a known working donor monitor. If the problem migrates, then I know it's a CCFL issue."

Sounds good plan to me likewise if you have the panel off a donor try it on
these boards
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Old 04-14-2012, 06:21 PM   #11
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

Quote:
Originally Posted by smalltownguy View Post
I DO have a few spares at work to check for possible CCFL failure, but I really don't want to pull apart another 22" panel that's in constant use unless I absolutely have to. These things are heavy and awkward.
See budm's thread on "Inverter tester using old CFL"

http://www.badcaps.net/forum/showthread.php?t=19987
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Old 04-17-2012, 09:25 PM   #12
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

Update: I brought a sister monitor home today and swapped in the boards from the known good monitor with my panel. I gave it to my wife to work on all day with her design work.

Result: no problems all day.

OK, that's good, at least that means I've narrowed the issue down to the inverter or logic board(s).

So what now? Start stressing my suspect boards with brightness adjustments, or a hair dryer?
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Old 04-17-2012, 09:52 PM   #13
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

A photo of your inverter board would be helpful.
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Old 04-17-2012, 09:59 PM   #14
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

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Originally Posted by jetadm123 View Post
A photo of your inverter board would be helpful.
Eh?

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Old 04-17-2012, 10:03 PM   #15
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

Oops! Been looking at too many Dell boards today. Some of them had separate inverter boards.
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Old 04-17-2012, 10:08 PM   #16
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

"I metered the blue caps near the transformers and got similar ohms between the two (secondaries, right?)"
So are you able to read the resistance of these two blue ballast caps?
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Old 04-17-2012, 10:10 PM   #17
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

Quote:
Originally Posted by budm View Post
"I metered the blue caps near the transformers and got similar ohms between the two (secondaries, right?)"
So are you able to read the resistance of these two blue ballast caps?
How do you do that?

I did test all the caps on both boards with my ESR meter.
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Old 04-17-2012, 10:14 PM   #18
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

I am just trying to find out if the two ballast caps have leakage resistance when you check them with the Ohm meter.
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Old 04-18-2012, 02:20 AM   #19
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

Try to replace C806.

I had the same symptom with the same IPboard.
I used hot-air to locate heat affected component then found C806 conduct when it heat, replaced with 0.1uF/50V 0805 running fine for 2 months.
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Old 04-18-2012, 06:26 AM   #20
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Default Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

Cant see C806 is that a ceramic smd on the back?
What voltages do you get on the two black caps in the inverter side of the PS (one is possibly c805)
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