Dell 2407WFPb Monitor - Bad Cap

[Rtech]

Re: Dell 2407WFPb Monitor - Bad Cap

I have just done a by pass today,and the Monitor switched on using a 19.5v 3.950amp Power pack.The screen was very good EXCEPT for some slight distortion which looked like small waves travelling across the screen.The first thing was to try the refresh rate,and it was better at 60Hz then anything else higher.I assumed then it was probably poor regulation from the 'cheapo' power pack,and replacing it with a 20V 7amp power supply resulted in a perfect picture.This pack had an internal fan which switched on after about an hour or so,so suspect you probably need a good quality one with a minimum of 5amps at the 20V(100W).

[Fhajad]

Re: Dell 2407WFPb Monitor - Bad Cap

I was gonna grab a 20v/100w actually. Where should I look for one that has the same size barrel connector? Or should I just get a universal?

[Rtech]

Re: Dell 2407WFPb Monitor - Bad Cap

Probably the universal may be the answer.

[Fhajad]

Re: Dell 2407WFPb Monitor - Bad Cap

Does anyone have a link to good priced universal power adapter? I haven't been able to find anything that meets the specs required even.

I best I can find is this: http://www.newegg.com/Product/Produc...82E16834992859 but its 20v output limits it to a max of 4.5amps.

[Fhajad]

Re: Dell 2407WFPb Monitor - Bad Cap

No one with any better suggestions?

[budm]

Re: Dell 2407WFPb Monitor - Bad Cap

http://www.ebay.com/itm/4-Pin-160W-A...ht_2863wt_1186

http://www.ebay.com/itm/AC-Adapter-D...ht_1337wt_1186

[Fhajad]

Re: Dell 2407WFPb Monitor - Bad Cap

Those supplies wouldn't work though due to the pin connector?

[budm]

Re: Dell 2407WFPb Monitor - Bad Cap

You will have to cut connector out since your monitor is not made for external power supply any way to connect it to your monitor, it has four pins, one pair for +, one pair for -.
You can ask the seller on the pinout.

[Fhajad]

Re: Dell 2407WFPb Monitor - Bad Cap

I guess I should ask, what's the voltage/amperage we should be aiming for. I've looked back and seen 19-20v from people from 5amp-8amps. I know the amperage you can go over, the biggest issue is the voltage. Is there a concern of what the usable voltage range is?

[budm]

Re: Dell 2407WFPb Monitor - Bad Cap

19~20V will be fine since the voltage will get step-down to run the low voltage circuits, the 19~20 will be used directly for the inverter circuits which is not critical.
Higher amp rating will make it run cooler.
Per Dell, the max power is 110W.
http://support.dell.com/support/edoc...P/en/about.htm
As you can see in my picture, I measure it to be about 19V.
http://s807.photobucket.com/albums/y...t=DSC00067.jpg

[Fhajad]

Re: Dell 2407WFPb Monitor - Bad Cap

If that's the case, I'm thinking if just getting that one off Newegg, run it at 19v, that'll allow 100watts continuous no problemo. It won't require any re-splicing of end connectors as well.

[budm]

Re: Dell 2407WFPb Monitor - Bad Cap

I would not get less power than it needs without any head room. Min is 110W. The spec also show in rush current, the 100W may not be able to handle the inrush and may go into shutdown due to current spike. You can try.

[Fhajad]

Re: Dell 2407WFPb Monitor - Bad Cap

On that 110watt spec it shows that's if you have all USB ports and the speakers running, and this would be assuming on a white screen with max brightness and everything on max. Since I wont be using the speakers, and the brightness not on max, it should be okay. Other people reported using less power fine earlier in this thread as well, so I'd imagine 100w being able to handle the inrush. We'll see in 2-3 days.

For the bypass wire, it looks like the wire connects to both C713 and F701, correct? I'm going to solder that all together today, just don't want to accidently blow it up.

[budm]

Re: Dell 2407WFPb Monitor - Bad Cap

I have never done one by pass, so I do not have the details or look at the board to see where the feeding point should be on the board. I will have to open up my monitor to see. I would believe it should be where the rectifier of the secondary side is connected, I would remove the old rectifier even though it will be in reverse bias mode.

[Fhajad]

Re: Dell 2407WFPb Monitor - Bad Cap

According to https://www.badcaps.net/forum/showpo...&postcount=155

It says "3) Run a decent gauge stranded, insulated wire between the points marked with an orange line. To get a good solder joint on the land between C713 and F701 scrape away the lacquer first. The other end of this wire goes down onto the middle pin of socket CN703 which is already quite well exposed for soldering."

I'm assuming this means to scrape away until I get to copper in the area between C713 and F701, then solder to that spot. I looked at my board and it doesn't seem to land on a individual spot.

There's also a picture on 151: https://www.badcaps.net/forum/showpo...&postcount=151

[Rtech]

Re: Dell 2407WFPb Monitor - Bad Cap

From the Positive centre pin of the input socket(wich was the power out socket for the 12v Sound bar). to the positive side of all the line of caps.ALSO do not forget to take the little coil out that was used to privide the 12v to the socket.

[Kaixin]

Re: Dell 2407WFPb Monitor - Bad Cap

Kudos to AdrianM! You are definitely a genius!!! Got mine fixed now. Tons of thanks. Recommend everyone to do the magic formula as described by AdrianM in post #155. Cheers!

Got it fixed now. New approach though. I began to wonder what voltage(s) were supposed to be produced by the SMPS so traced out the circuit around the output transformer. The feedback for the buck stage is obtained via an opto switch that comes on at about 20V (determined by a LM431 variable Zener). Just the one 20V supply rail then! A quick hookup to a bench supply confirms a happy monitor when juiced by 20V@3A.

Because the final output is a bunch of diodes fed from the switching transformer, it's OK to run an external 20V supply straight onto the board (across the row of 470u/35V caps). The diodes block current from going back into the transformer. I tweaked the voltage around and monitored the opto switch switch-on point confirming that the SMPS is set to run at 20V.

Now, I remembered that I had a spare power brick from my previous Dell monitor and sure enough it's rated 20V@3.5A. Not only that, but the DC jack fits the Loudspeaker output - so I cut the inductor (L702) that fed it power from the main board and jumpered a wire to the 20V rail (photo). I also grounded the switch contact that tells the MB the speaker isn't plugged in, even though the power plug is in. Oh, and I left the fuse off the SMPS just incase it ever gets plugged into the mains by accident!

[budm]

Re: Dell 2407WFPb Monitor - Bad Cap

Please notes that max power requirement is 110W per spec from Dell, if you do not run at full brightness and loud sound, then 70Watts power supply may be OK, there will be no head room and some adapter may startup ok some may not due to monitor high inrush current of 40A (see post 310) which some adapter may not be able to handle and will go into shutdown mode.
Here is the voltage reading of the power supply:
http://s807.photobucket.com/albums/y...t=DSC00067.jpg
Check the temperature of the adapter if you are going to use lower wattage than what the monitor needs, since the adapter is a sealed unit with no vents, if it too hot to touch then the inside will be even hotter and that is a killer for the components inside.

[Fhajad]

Re: Dell 2407WFPb Monitor - Bad Cap

Well the adapter I bought works. I just have a large dark splotch on the left and it's kinda dark strip in the right edge, but it works fine it appears, no issues thus far.

Although I did just have it darken out on me and I had to turn it off and back on to get it back on. Appears to be my lil' power adapter can't handle too much brightness before it auto powers off. Seems to work ok at 60 and below.

[micdis]

Re: Dell 2407WFPb Monitor - Bad Cap

Ok, you should all really stop discussing solutions! The solution to repair the powerboard has passed this topic a few times now:

Buy these parts (farnell number = first number):
1469418 VISHAY SEMICONDUCTOR TZMC15-GS08 DIODE, ZENER, 15V, 0.5W
1828683 PANASONIC CAPACITOR, SNAP-IN, 450V, 120UF
2*1903859 MULTICOMP RESISTOR, WIREWOUND, 0R47, 5%,
1652430 SEMICONDUCTOR NCP1200D100R2G
9882464 STMICROELECTRONICS
9935517 STMICROELECTRONICS STP10NK60ZFP MOSFET, N, TO-220FP
1354592 LITTELFUSE 0234004.MXP FUSE, MEDIUM DELAY, 4A
1162740 SCHURTER 0031.8201 FUSE HOLDER, PCB,
9693904 ECA2AM010 CAPACITOR, 1UF, 100V (optional to replace)
& 1k resistor in 0805 size or 1206


And replace:
-C605 120uF/450V
-Q651 STP10NK60ZFP
-IC651 L6561D
-R669 1k 1206
-ZD601 15V 0.5W (diode)
-IC601 NCP1200D
-R670 = 2*0.47ohm together parallel (makes 0.23ohm)

This will definitely solve most of the problems! Pictures with the pieces that should be replaced are attached. These are images of a repaired working board.

Fixed 2 Dell 2407WFPb screens with the replacement of these parts.

Just go 3 pages back, the solution is there for you!
https://www.badcaps.net/forum/showpo...3&postcount=77
I did those steps on a 4H.L2K02.A01 board, and it's working now! Had the same problems with the burned resistor. Thanks's btw endor!!!! Had to order the parts but it works like a charm, now.