Dell E228WFPC goes dim after 10 minutes, not 2 seconds

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  • selldoor
    replied
    Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

    Are c805 and C 811 the two caps on the inverter section.
    Did you measure the voltage at them yet
    I dont think we know yet that the c806 is a problem on your board.
    Try easy things first.

    I suppose setting it up then heating where c806 is to see if it makes it go off would be a test
    Last edited by selldoor; 04-19-2012, 12:52 PM.

    Leave a comment:


  • Jasgriff
    replied
    Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

    These are easy to do if u smother the end in solder and quickly heat up both sides then lift using tweezers or push to the side with the soldering iron.

    Smd caps can be bought from the usual places. Can't see ur location on your profile so not are where to suggest.

    Leave a comment:


  • smalltownguy
    replied
    Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

    FYI - I replaced C805 and C811 today (470uf 25v each) and no change. On the off chance that POM_MJ meant C805 instead of C806. I didn't check this thread for updates until AFTER I'd swapped out those caps.

    OK, I'm pretty handy with a soldering iron, but WTF?

    How am I supposed to change that surface mounted cap?

    Metal tweezers and a low temp iron with a pencil tip?

    Where can I find said cap?

    Leave a comment:


  • budm
    replied
    Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

    That makes sense since it is hooked up as softstart, but with resistor in place (leaky cap), then it is setup as Deadtime control.

    Leave a comment:


  • POM_MJ
    replied
    Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

    When BAD C806 (in my case) warmed-up, it has leakage current flow through it then cause the voltage at PIN4 goes higher than normal and pulse duty cycle goes wrong, that make lamps current incorrect, then protection scheme shutdown the oscillator, I thought.

    edit: IPboard 715G2594-1-4 (HUDSON8) schematic uploaded for reference.
    Attached Files
    Last edited by POM_MJ; 04-18-2012, 10:18 PM. Reason: schematic uploaded

    Leave a comment:


  • budm
    replied
    Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

    I look at the SCH, PIN 4 is the Dead time controller pin, per SCH, it is setup as SOFT-START mode since R818 is not used. It is interestin that C806 caused the lamps to go dim, it must have change the ON time of the lamps.
    Attached Files

    Leave a comment:


  • budm
    replied
    Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

    Edited: Thanks for in pictures, POM MJ.
    Last edited by budm; 04-18-2012, 09:24 AM.

    Leave a comment:


  • POM_MJ
    replied
    Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

    pictures uploaded for reference.
    Attached Files

    Leave a comment:


  • selldoor
    replied
    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)

    Leave a comment:


  • POM_MJ
    replied
    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.

    Leave a comment:


  • budm
    replied
    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.

    Leave a comment:


  • smalltownguy
    replied
    Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

    Originally posted by budm
    "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.

    Leave a comment:


  • budm
    replied
    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?

    Leave a comment:


  • jetadm123
    replied
    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.

    Leave a comment:


  • smalltownguy
    replied
    Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

    Originally posted by jetadm123
    A photo of your inverter board would be helpful.
    Eh?

    Leave a comment:


  • jetadm123
    replied
    Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

    A photo of your inverter board would be helpful.

    Leave a comment:


  • smalltownguy
    replied
    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?

    Leave a comment:


  • retiredcaps
    replied
    Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

    Originally posted by smalltownguy
    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"

    https://www.badcaps.net/forum/showthread.php?t=19987

    Leave a comment:


  • selldoor
    replied
    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

    Leave a comment:


  • retiredcaps
    replied
    Re: Dell E228WFPC goes dim after 10 minutes, not 2 seconds

    Originally posted by smalltownguy
    Hm....I'll have to try that.
    Or try the converse. Pump the brightness and contrast to max.

    Leave a comment:

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