Dell U2410f

[budm]

Re: Dell U2410f

FR= Fusible resistor, they use resistor as a fuse since it can take higher surge current than slo-blo fuse.
I will look at all the pictures later on today to see how this monitor works.

[wasmundt]

Re: Dell U2410f

"it should have a bour 165VDC when the monitor is plugged in, then it should go up to 390~400V when power up (if your line voltage is 120vac). When work on primary side of the circuit, do not use the chassis as the ground ref, you have to use the negative leg of the cap as the ground ref point.

Thanks for the info about what to use for the measurements..

Even minus the resistor I blew out, not sure if I should have turned it on again after that but nothing further went boom. The capacitor is seeing a 160 V load from the +/- terminals when it is turned on/plugged in. It doesn't seem to ramp up at all. Though, that may have been because of the blown resistor, but I highly doubt that as I was getting those readings before.

Thank you very much for all your help! Appreciate it a lot.

~Sam

[budm]

Re: Dell U2410f

I just hope that more parts are damaged. If the voltage on the cap did not go up (before the resistor is damaged), then it may be that the main board does not send out the PS_ON to turn on the power supply, but something does not make sense is that you do have 24vdc for the inverter board so the PS_ON is OK, at the same time, this PS_ON is also turn on the PFC Voltage booster circuits.
So more in-depth troubleshooting will be required.

[wasmundt]

Re: Dell U2410f

hey budm, tell me what else you would like me to take measurements on and I'll be mroe then happy to. If you need more pictures just let me know for that too. I have a nice DSLR camera I can take them with

I think I found the resistor, or pretty darn close to what I burn out - but am not sure where to pick them up at as it's a company based in China. If you have any suggestions for an alternative I'm all ears.

Here's the page: http://www.futaba.com.tw/English/P13.htm

<forum moderator, if this isn't allowed please let me know and I'll just attach a screeny of it instead>

[budm]

Re: Dell U2410f

I will have to download all the pictures and see how the monitor is setup and see where I can tell you the test points will be. I may ask for more pictures since my eyes are not that great.
What resistors do you have laying around? I will have to tell you first to check and see if there are anything else that may have been damaged when the resistor burnt up, we do not want to power this thing until we find out if anything shorted out or not.

[wasmundt]

Re: Dell U2410f

well I don't really have anything just laying around - I am interning in Arizona, so not much made the trip with me over from the midwest. I can swing by Radio Shack and pick up whatever you suggest. As far as not turning it on, I've already messed that one up.. it turned on and nothing started smoking so don't think anything else got shorted/burned out when I messed it up.

Please just let me know whatever places you would like a closer view of and I'll be more then happy to snap a photo.

One thing to note before we get too deep into this, when desoldering this fusible resistor, I did accidently pull up the copper rings they were fed through on the board. I figure with enough solder inplace this shouldn't be a deal breaker, but if it is let me know and I'll just scrap the project or try and get those metal pieces off the blown resistor legs..

From a physical circuit standpoint, I don't think the cross talk / inductance shielding this is removing will have to large of an effect, but you if you feel otherwise let me know.

[wasmundt]

Re: Dell U2410f

Is there anything you would suggest I order online, or pickup from Radio Shack to replace the Fusible Resistor?

[budm]

Re: Dell U2410f

Can I get a clear straight shot of the pictures? I cannot see the traces well.

[budm]

Re: Dell U2410f

Since that fusible resistor FR851 blown up, it can be that the MOSFET Q853 is shorted out or you may have shorted the bottom end of FR851 to primary circuit ground.
You need to check the resistance of Q853 between S and D, S and G, D and G to make sure it is not shorted out. We need to get this PFC circuit working again.
I draw up the diagram as good as I can get from the pictures.

[budm]

Re: Dell U2410f

Can I also get the LCD panel P/N so I can look up the spec sheet? it will tell us the pinout of the inverter board.
Also closed up and focused pictures in red circles.

[wasmundt]

Re: Dell U2410f

Just wanted to let you know that I won't be able to get to these pictures until late this evening.

~Sam

[wasmundt]

Re: Dell U2410f

I believe the P/N is KLS-LM240SH-HV Rev:0.3 94-0 the other number on the board is 6632L-0507C which is close to the right circle in the last post.

[wasmundt]

Re: Dell U2410f

Since that fusible resistor FR851 blown up, it can be that the MOSFET Q853 is shorted out or you may have shorted the bottom end of FR851 to primary circuit ground.
You need to check the resistance of Q853 between S and D, S and G, D and G to make sure it is not shorted out. We need to get this PFC circuit working again.
I draw up the diagram as good as I can get from the pictures.

I'm pretty sure what happened was I grounded out the resistor. Not smart on my part.. Regardless, the resistance readings I'm seeing across Q853 is SG: .6, SD: 2, and DG: 2.4 a bit rusty, but from what I was reading on another post if any of the readings are less the 30 ohms it's probably shorted out. This very well could be the case.. idk, I think the best thing will to get my blunder patched up and then begin solving the original issue

[wasmundt]

Re: Dell U2410f

I took measurement resistance measurements on the Q950 and Q850 MOSFET and had measurements as follows on the 20k MM setting.

Q950: GS - 9.43, SD - 0.L, DG - 0.L
Q550: GS - 9.16, SD - 0.L, DG - 0.L

So it does indeed look like the Q853 MOSFET was shorted out as well.

I also did notice a small dark mark on the bottom side of the board that I've attached a picture of. I'm not sure if this would cause anything to be a problem or not, but wanted to note it.

[sebr]

Re: Dell U2410f

The reading "0.L" on your meter usually indicates infinite resistance - so just the opposite of a short.
Besides that I would highly recommend to exchange the primary cap! While primary caps rarely tend to fail, this Elite brand cap is well known for bringing down many Dell screens including some damage to other components. Watch out for the dimensions when you try to find a replacement!

[wasmundt]

Re: Dell U2410f

the resistance readings I'm seeing across Q853 is SG: .6, SD: 2, and DG: 2.4

These are the reading across the MOSFET in question, I realized the difference between 0.0 and 0.L thanks for looking out for a misconception though.

So far my parts list I need to replace will be the .2 Ohm FR (though not sure on what wattage rating to get), the mosfet Q853, and possibly C854 the 120/450V behemoth.

[sebr]

Re: Dell U2410f

You can determine the wattage by the physical dimensions of the resistor. Well, there are special fuses resistors out there but usually any percision resistor with same resistance and wattage should do the job.
Maybe this is of interest for you:

[wasmundt]

Re: Dell U2410f

budm, do you agree this MOSFET should be replaced?

[budm]

Re: Dell U2410f

So the reading of Q853 is taken with it removed from the board? I would like you to take the reading with that (Q853 removed) between the Gate and the Source circuit board pads to see what you get, just want to make sure the PFC IC output is not damaged when Q853 got damaged.

[wasmundt]

Re: Dell U2410f

Ok, I'll remove Q853, but to clarify what reading would you like me to take with it out? I'll take readings on the Q853 itself, but on the board you want V or R readings? I assume resistance readings with the power off. By board pads, you mean where the Gate/Source pins were previously at correct?