Dell E228WFPC goes dim after 10 minutes, not 2 seconds

[POM_MJ]

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

pictures uploaded for reference.

[budm]

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

Edited: Thanks for in pictures, POM MJ.

[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.

[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

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

[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?

[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.

[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

[smalltownguy]

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

Yes, C805 and C811 are in the inverter section. They're both located right next to the CCFL tranformers.

You want me to measure the voltage at each cap while the monitor is on? That might be kind of a trick, but I think I can pull it off.

[smalltownguy]

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.

I live very close to DigiKey, so most of my orders are 1-day shipping from them. If you can get me a part number, I just placed an order with them a few hours ago, I'll see if I can add the item to my order.

Thanks!

[selldoor]

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

Yes - I was told you had 3 arms and 4 pairs of hands and were brilliant at twister.

[Jasgriff]

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

And if you can do all that and take a pic of ur multimeter at the same time Retiredcaps will defo allocate you some extra points.

Which SMD cap do you want us to find on Digikey for you?

[budm]

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

I think he he is talking about C806 in post 21, 1uF 16V MLCC. But I think he should try heating up the cap as suggested in the post by POM_MJ, that was how he found out that he has leakey cap.

[smalltownguy]

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

Yeah, I'll heat the cap first before ordering it.

[budm]

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

@smalltownguy, do you have any through hole type caps? Anything like 0.47uf or so?

[smalltownguy]

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

@smalltownguy, do you have any through hole type caps? Anything like 0.47uf or so?

Sure I do - what are you thinking?

[budm]

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

If the C806 is bad after heat test, then you can use just one 0.47uF or two in parallel to see if that will work, you just have to find solder pads that are connected to the C806 and solder in the through hole caps in place.

[smalltownguy]

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

I rigged up the monitor with clear access to the back of the inverter board and turned it on. I hit it with the hair dryer and within seconds, it shut off.

So...heat is definitely causing a problem.

I'll see if I can get a better look at the board to find a suitable location to add a .047 cap to it, unless someone else thinks it's a better idea to just wait and order the surface mount cap?

[budm]

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

You will will have to remove bad cap from the board, then install a new cap in place, like I said, try using the cap in place of the bad one you find just to verify that the cap will fix your problem.

[jetadm123]

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

I rigged up the monitor with clear access to the back of the inverter board and turned it on. I hit it with the hair dryer and within seconds, it shut off.

So...heat is definitely causing a problem.

I'll see if I can get a better look at the board to find a suitable location to add a .047 cap to it, unless someone else thinks it's a better idea to just wait and order the surface mount cap?

I think I see a few things that should be clarified:

1) I think when POM_MJ mentioned "0805" back in post #19, it might have been interpreted as "C805". 0805 defines the case style of the smd cap he used. It defines a specific length and width.

2) Since the original cap is 1uf 16V, budm specified connecting two .47uf caps (not the 0.047uf that you mentioned above) in parallel, which gives a total of 0.94uf (close enough to the desired 1 uf). Also, pre-bend the leads of the caps before you solder them in, as bending them afterwards will lift the pads off the circuit board.

3) To remove C806, if you have access to a second soldering iron, hold an iron in each hand and heat both ends of C806 at the same time.

4) If you opt to order a surface mount cap for C806, then the proper value is: 1uf 16V, case style 0603.