Dell 2407WFPb Monitor - Bad Cap

[MPX]

Re: Dell 2407WFPb Monitor - Bad Cap

Q653 and D655 are also defect, anyone an idea for a replacement?

[selldoor]

Re: Dell 2407WFPb Monitor - Bad Cap

Q653 and D655 are also defect, anyone an idea for a replacement?

Any part numbers visible

[MPX]

It's a FET

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[selldoor]

Re: Dell 2407WFPb Monitor - Bad Cap

Only thing I can find that might be anywhere near is this
http://www.alldatasheet.com/datashee.../2N7002KW.html

It says the marking is "7KW" but does not refer to HI or Hl or H1

[MPX]

Re: Dell 2407WFPb Monitor - Bad Cap

Farnell has a few 2N7002's without "KW"
I could give it a try and order 1859847 or 9512608
Thanks, I appreciate your search.

[sebr]

Re: Dell 2407WFPb Monitor - Bad Cap

I would be interested to know what replacement you used for D655?
This diode is between the driver IC and the gate of Q651 along with R668.

[MPX]

Re: Dell 2407WFPb Monitor - Bad Cap

This is my replacement list, Q653 was not defect.

C605 120uF/450V Farnell 1828683
IC651 L6561D Farnell 9882464
IC601 NCP1200D Farnell 1652430
Q654: MM3906 Farnell 1773629
Q651 STP10NK60ZFP Farnell 9935517
D655 1N4148
R670 0.22ohm Farnell 1903854 (10)
Fuse 4A

I have used the original fuse holder.

[selldoor]

Re: Dell 2407WFPb Monitor - Bad Cap

Hi MPX - so are you saying you got it up and running now?

[MPX]

Hi MPX - so are you saying you got it up and running now?

Yep

[jetadm123]

Re: Dell 2407WFPb Monitor - Bad Cap

Congrats on the fix. I'll share one of my observations about the repair parts used. It would seem the original PWM controller was a 200A6, which some people are replacing with a 200D1. The main differences between the two is that the 200A6 runs at a fixed frequency of 60kHz versus 100kHz for the 200D1. Also, the 200A6 has a higher DRV output than the 200D1. Interesting that the power supply still works with the higher fixed frequency.

[r-p]

Re: Dell 2407WFPb Monitor - Bad Cap

Short version: it functions again with the external powersupply modification.

Thanks AdrianM and all other posters.

Longer version:

I salvaged this monitor from my neighbor, but he had put it out in the rain and snow for a week or two before I got my hands on it...

120uF cap was bad, fuse was blown. Replaced with 100uF 400V and correct fuse. Switched it on, a big bang and unplugged it again. Fuse still in one piece, but monitor not functioning.
Found one of the 0.22ohm resistors to be blown, desoldered the fet next to it, but put it back after reading its number (K3502) and finding out it's not a normal transistor (= easier to measure for correct functioning, don't know how to test FET's properly).

Replaced 0.22ohm resistor with 5W version I had lying around, switched it on, blew the fuse and gave up and went for the external power supply option.

One thing I did find is that it wouldn't stay on for long (just few seconds) at 19V. It only functioned properly above 22V*. Do note this was using some crocodile clamps to get the current through the speaker-power-connector and the 22V was measured at the powersupply, not at the plug or even on the board.

I ended up using a 24V 2.3A SMPS that I had lying around. It may not be powerfull enough for longer periods: iirc it drew around 2.5A from my lab-powersupply. I wanted to put in an official DELL-socket from a docking station, but am not convinced the 19.5V DELL laptop powersupply (I have spare 4.5 and 6.7A that I don't want to cut the plug of off) would power it... So didn't find it worth the hassle.

So thanks! It at least does something again, too bad I bought a 23" LED a month back

May try to read all 18 pages again to see if I can still salvage the powersupply board with stuff lying around...

Thanks guys, great site!

*: my lab power supply is a Delta Electronics 0-30V, 0-10A SMPS, where I just noticed last week that the main capacitor has some kind of lacquer between its poles that has cracked. Rest seems fine, but will try to desolder and measure capacity (390uF, 400V) shortly.
The internal voltage display is off a little, and I did not measure the voltage with a multimeter but still fairly certain the voltage had to be above 20V for the display to function. 2.5mm^2 measuring leads 1m long and internally I used a ~12cm length of 0.75mm^2 which should cope with the 2-3A needed quite happily.

[r-p]

Re: Dell 2407WFPb Monitor - Bad Cap

Edit: the monitor works fine on 19.5V (~3.2A) or on 24V (~2.5A). I think my switching powersupply is on its way out. These measurements were taken with a 10,000uF cap on the powersupply-output to soften the peakcurrent of the display switching ON and its current-limiting LED was continuously flickering (at ~3A while it is a 10A powersupply and the currentlimiting was at maximum).
I also rigged up a different setup, so no crocodile clamps this time.

This means I will probably indeed put in an official DELL-socket so I can use my laptop-supplies (or my 12V->20V supply with DELL identifying chip for use in my camper/RV)
DELL chip from a broken powersupply later attached to a NON-DELL supply to get full functionality.

[Engrken]

Re: Dell 2407WFPb Monitor - Bad Cap

The input power converter bypass described by Adrian in Dec 2011 saved my Dell 2407WFPb. I'm very grateful. The external "brick" supply is rated 19V @ 3.79 A (72 W) and works well but runs hotter than I'd like. My perception from what has gone before on this site is that the input power converter contains so many interdependent highly stressed parts that reliability will certainly suffer. Also, here in the U.S. our 120 VAC power mains put only ~160 VDC on C605 which is a reminder that the primary purpose of that input power conditioner is to accept 100 to 240 VAC at 50 or 60 Hz.

[sebr]

Re: Dell 2407WFPb Monitor - Bad Cap

I am looking for C621? mine is broken is burned

As I had this cap blown too lately (beside many other parts, but got it back working ) so replace it with a 10 nF ceramic cap, Farnell 1833850.
Just in case somebody else looking for this information

[hartklep]

Re: Dell 2407WFPb Monitor - Bad Cap

Hello,
I used the same parts list from mr MPX on post 347.
And I need olso a new ZD 601 and and a new R669.
Everything works fine again.
Thanks for all the help.

[deadvirusllc]

Re: Dell 2407WFPb Monitor - Bad Cap

Ill be damned! Was gonna toss this thing after replacing all the other pcbs and fuses. Didnt know that fuse was there.

[deadvirusllc]

Re: Dell 2407WFPb Monitor - Bad Cap

Hi there...
Since my WFP2407 stopped working yesterday and I have no service-tag (and the dealer I bought my display from is not doing anything regarding to PC-stuff anymore) I descided to open up my Display.

It was the F1 fuse that was broken (measured several M-Ohm inside the circuit over the fuse). So I searched through my boxes with stuff and found some old glass-fuses rated 2.5A. I did assume that the 2.0 on the fuse stands for 2.0A so 2.5A was close enough for me to test.

The Fuse with some wires soldered to it:


The replacement Fuse:


After the usual seconds of doubt I plugged in the device and got the DELL-Logo, it was alive again! Nice...

Since I cannot get my hands on a 2.0A SMD-Fuse currently I decided to just clean up the stuff I did a bit and repack my Display until I get a nicer fuse.

A bit nicer:


I think I will try to get my hands on
BOURNS - SF-1206S200-2 - FUSE, SMD, 1206, 2A
since the dimension fits, it is a slow fuse and rated 2.0A. But the minimum order value at Farnell (and resellers for private persons) keeps me off from testing it right now.

Maybe someone gets here via google (just like me) and gets motivated by the pictures

Regards

That fuse was my problem! I checked every fuse and didnt know that one was hiding there! Two years later and that post solved my problem.

[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

@engrken, please see the spec. 73w power supply is too low.

[sirzur]

Re: Dell 2407WFPb Monitor - Bad Cap

Also trying to troubleshoot this PSU board.

Can someone who has a spare of this board (not in a monitor) do some measurement?

I want to find out the resistance between the 3 legs of Q651 when it is on the board. I get a very small resistance between the 3 legs (about 115 ohm)

Also what is the resistance across the Zener diode ZD601 on the board? Again, I get a small resistance.

Second last question - would a 2W rating be sufficient for Resistor R670 (0.23 ohm)?. I note in the Farnell part number that the rating is 3W

I am thinking of sourcing everything from ebay - found some Nippon KXJ 120 uF, 450V capacitors. Anybody has experience with these? I know the general consensus is to use Panasonic or Rubycon caps.

[RethoricalCheese]

Re: Dell 2407WFPb Monitor - Bad Cap

If the large cap seems fine, it 99% of the time is fine so there is no need to change it. Atleast I have never had to change it, fixing about 200 LCD-s (except one that was hit by a lightning)