Dell E228WFPC goes dim after 10 minutes, not 2 seconds

[selldoor]

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

[Jasgriff]

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.

[smalltownguy]

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?

[budm]

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.

[POM_MJ]

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.

[budm]

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.

[budm]

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

Edited: Thanks for in pictures, POM MJ.

[POM_MJ]

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

pictures uploaded for reference.

[selldoor]

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)

[POM_MJ]

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.

[budm]

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.

[smalltownguy]

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?

How do you do that?

I did test all the caps on both boards with my ESR meter.

[budm]

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?

[jetadm123]

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.

[smalltownguy]

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

A photo of your inverter board would be helpful.

Eh?

[jetadm123]

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

A photo of your inverter board would be helpful.

[smalltownguy]

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?

[retiredcaps]

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

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

[selldoor]

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

[retiredcaps]

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

Hm....I'll have to try that.

Or try the converse. Pump the brightness and contrast to max.