Dell 2407WFPb Monitor - Bad Cap

[selldoor]

Re: Dell 2407WFPb Monitor - Bad Cap

Plastic knives, forks, spoons. Chop off the handle and sharpen it/refine it to make it do what you need. Find a sturdy one whose handle doesn't bend.

Toothbrushes cut up well to make scrapers, prodders and even screwdrivers
and have a sturdy easy to grip handle. Can also be used for brushing

[Tyan]

Re: Dell 2407WFPb Monitor - Bad Cap

Tyan, the speaker socket/power mod is a simple three-step process:

*snip*

1000 Thanks, U ROCK!

I´ve just ordered a power brick 20V / 90W. I hope, my last 3 attempts to fix the board didn´t kill something essential.

[Tyan]

Re: Dell 2407WFPb Monitor - Bad Cap

everything worked out pretty fine!

I chose the "simple" way and cut the little L702, after the solder refused to melt... And I made a little solder blop to bridge the socket (green arrow). Heres a pic (ignore the orange and yellow arrows):



After plugging in the new, external SPU in the single board nothing happened. Which was a good thing, all attempts before lead to a Tyan standing in a quite dark kitchen

So i plugged the board in, powered it up, lifted the screen (laying face down on a towel) an saw a beatiful, animated Dell logo. I wish you all the same feeling as I had that moment

The external power brick is getting quite warm, but acceptable. Also now there is no electrical grounding anymore, since the speaker-out and the power supply don´t feature this. But I´m confident that this shouldn´t lead to any problems. Maybe I´ll install an additional socket ELCB.

Again: many, many THANKS to AdrianM

[newbie1]

Re: Dell 2407WFPb Monitor - Bad Cap

Congrats Tyan.. As for me, i managed to buy a used 20v 3.15A 60w power adaptor but seems like my screen is not performing as well as i hoped for.

Hopefully, those black patches are not pressure marks resulting from something pushing/pressing against the screen. Those type of marks are not repairable.

jetadm123, i think my panel has massive 'white' patches on a black background instead of the black patches. When the screen is having white background & viewing directly straight at it there isn't any visual problem. But, when it is having black background & viewing at an angle, white patches are plastered all over the screen. I will try to take an image to show what i mean.

But, hey, i am not complaining. After months of troubleshooting, with the $$, sparks, fire, and fireworks it was just pure pleasure looking at the 'D...E...L...L' welcome screen with this modified version of the power adaptor. And I really have to thank AdrianM for it...

[newbie1]

Re: Dell 2407WFPb Monitor - Bad Cap

Attaches are the photos showing what i mean by white patches on dark/black background

[haxman]

Re: Dell 2407WFPb Monitor - Bad Cap

Thats a shame newbie1, what does it look like when say on the desktop?

Thanks for the guide, i have also rewired the powersupply according to your instructions, just waiting on the DC power pack to come.

/fingers crossed.

[newbie1]

Re: Dell 2407WFPb Monitor - Bad Cap

It is fine on a white background..
Just note, that my power adaptor connector is a bit loose so once in a while there will be blank/white screen. So you will need to adjust the connector as mentioned by AdrianM.. All the best to you!

[karkera]

Re: Dell 2407WFPb Monitor - Bad Cap

I need a DELL 2407WFPb service / schematic diagram ... the same power problem (ON) problems.

Regards for help

[haxman]

Re: Dell 2407WFPb Monitor - Bad Cap

Thanks Adrian, I now officialy love you.

Monitor fired up and worked perfectly.

So much difference between this monitor and my old TN panel. not bad for the price I paid (10 dollars for monitor + 15 for the power pack).

[Tyan]

Re: Dell 2407WFPb Monitor - Bad Cap

at my place the Monitor is now standing next to a Dell U2412. And what I can say is: the old 2407 has better colours, yes. But the backlighting is no match to the LEDs of it´s younger brother. It takes ~10-15 minutes til the CCFLs reach the set brightness (50%).
And Ghosting is an issue, too.

[struppi]

Re: Dell 2407WFPb Monitor - Bad Cap

Hello
Sorry for the bad english
I am looking for C621? mine is broken is burned
--- R670 has 0.22 Ohm?

[protoquark]

Re: Dell 2407WFPb Monitor - Bad Cap

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!

I just picked one of these monitors up off the street last night, took it apart and found the 450V cap blown as have many others. I've removed the part and was planning on replacing it but was scared off by other people reporting multiple problems. I'd rather not spend any extra cash on this repair so my question is, is it possible to do this external brick power mod without the 450V capacitor inline? If not I'll happily replace it before doing this mod.

Thanks!

[dumpystig]

Re: Dell 2407WFPb Monitor - Bad Cap

You need to replace and install the 450V cap before going any further with troubleshooting. You may find it was the only fault and your monitor will work fine afterwards.

[zomi]

Re: Dell 2407WFPb Monitor - Bad Cap

the psu for the 2405 is very similar
will the external psu mod work for that also ?

[qlman]

Re: Dell 2407WFPb Monitor - Bad Cap

Tyan, the speaker socket/power mod is a simple three-step process:

1) In the photo attached below I have marked both ends of L702, which is to be removed from the PCB, with magenta crosses. De-solder or just cut both ends of this inductor (a bit of wire that passes through a ferrite bead on the component side). This isolates the power socket from it's normal supply circuit.

2) The short blue line shows where to solder a bridging wire to permanently ground the switched contact for the socket CN703 - making it seem that the speaker isn't plugged in. A blob of solder across C718 would also do the trick.

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.

That's really all there is to it! The central pin in the speaker socket may be a little smaller than the power-brick plug (2.1mm vs 2.5mm I think) If it doesn't connect very well, it might be necessary to roll a small piece of copper or tin shim to increase the diameter of the centre pin. If that's too fiddly then you can always swap the socket for the correct sized one, or find an adaptor lead. I slipped a slender wire crimp insert over the pin which worked a treat.

Iv done that on my psu and nothing, have 19.5v to inverter 19.5 to mainboard and that all, any sugestions ?

[soumen1]

Re: Dell 2407WFPb Monitor - Bad Cap

After 6 years of service my 2405fpw started emitting a high pitched whine, and died within two days. The 5A fuse on the 19 volt line from the SMPS board was open. Because a whine usually indicates dry caps, I recapped the SMPS. No more whine, and 19V and 7V supplies look normal.

Then I momentarily shorted the fuse to measure the current to the display PCB with an ammeter. One of the two FR9024N hexfets on the display PCB (the one close to the top edge of the PCB) heated up and shorted, along with the (Zener?) diode D19. (But it is possible that D19 was originally shorted and I did not notice it earlier. It is possible that D19 short was caused by SMPS failure, and then the shorted D19 destroyed the hexfet.)

Does anyone know the rated Zener voltage of D19? Or the normal voltage from the drain of the hexfet to ground? Is it worth replacing D19 and the FR9024N or are there guaranteed to be more toasted parts downstream?

[chappers]

Re: Dell 2407WFPb Monitor - Bad Cap

D19 won't have destroyed the hexfet; D19 is the protection zener, in place between source (ground - unless your source isn't going to ground, in which case the zener will go to ground but not source) and gate in case the MOSFET ever fails, going short-circuit drain to gate, and putting full drain voltage on the gate which would then destroy all of the gate driver circuitry. Instead, if drain voltage gets to the gate, the zener is there to fail s/c and drop the voltage straight to ground.

The failure of the MOSFET may not have damaged anything else, it depends on what it does. If it's being used as a buck converter, then voltage on the drain may have risen beyond the normal level and over-voltage may then have damaged whatever that power line is for. Generally that causes failures which are short-circuits. Put your meter between drain and ground and ensure you have a decent resistance there, otherwise you have a short-circuited part to hunt down. Source I gather is attached to ground, is it?

See if there's a similar arrangement on another MOSFET and check what voltage is on its gate, and if it uses a zener and the gate voltage is the same as where D19 resides, use the same value zener for D19. You can check these voltages because the monitor will work without the zener, you just don't have it protected if the MOSFET fails. If you're worried about doing that, just use the same value zener as any other MOSFET you can find, in the hope that it'll do its job if the new FET fails.

*I forgot to mention, the zener fails short-circuit, instead of just dropping the excess voltage that is over its rating, because it over-dissipates due to the voltage being much higher than its rating. So, this means ensuring that the zener is rated higher than the peak voltage on the gate, but much lower than the drain voltage which is supposed to cause it to fail if it ever sees it. So, if gate voltage was 2.5V, and drain 12V, then I'd stick a 3V zener in there, and not a high wattage one - you want it to fail, not cope!

[thewzard]

Re: Dell 2407WFPb Monitor - Bad Cap

I'm back. Sorry for the delay. I replaced the 450V capacitor with the correct capacitor and still nothing. Now I'm convinced that its not the capacitor. Perhaps its the fuse? I bought a cheap digital multimeter but I don't know how to use it. I have read online to put it in continuance mode but I don't think my multimeter has that functionality. Is there another way to test the fuse?

[budm]

Re: Dell 2407WFPb Monitor - Bad Cap

@thewzard, just put the meter in the Ohm mode, touch the two probe leads together, it should show around 1 or less Ohm, put the two probe on the fuse then you shoud see the same result if the fuse is good.
Brand and pictures of the meter?

[aResister]

Re: Dell 2407WFPb Monitor - Bad Cap

A note to AdrianM -- My Dell 2407WFPb Monitor blew out right in front of eyes recently. It first blew the circuit breaker on my UPS unit. After resetting the circuit breaker and turning it on again, I got a loud "pop" from the monitor. No more lightening strikes desired. I just knew the problem had to be power related rather than "screen" related. No power supply replacements available anywhere, of course. After taking the monitor apart and inspecting the PS, I noticed but one suspect part - Resistor R670. All other components looked to be in mint condition, unlike many of the bulging, blown and burnt components shown in many of the pictures on this thread.

Just the same, I wanted to replace the entire PS since few seemed to have any luck with changing out individual components. I just completed the modification for my power supply per your instructions and all is well. I did not have an external power supply (power brick) from another monitor, however I had a couple of 90 watt power supplies for the D-Series Dell laptops which I reasoned to be perfect for use on the Dell 2407WFPb. The only problem was that the plug on it was no match for the speaker power socket on this power supply, nor did I have any such spare socket that could be put in place of the speaker power socket on board the PS.

To get a socket, I tore apart an unused Dell D-Series Port Replicator and broke off a small chunk of its printed circuit board containing its power socket, then determined which of the connectors on that (now severely abbreviated) "mini" power circuit board provided 19.5 v DC as well as which was positive and which was negative. Then, I soldered one end of a simple light-wieght power cord (a typical lamp cord wire pair), after hacking its ends off, to the appropriate connectors on my "mini" power circuit board paying close attention to which was the positive wire and which was the negative.

The other end of this wire was soldered to the points on the monitor's power supply circuit board as you described--the positive wire to the center pin of the on-board speaker power socket and the negative wire to the "bridged" location on that power socket, performing the connector bridge step at the same time. Then, I routed a new single (decent gauged) stranded wire soldered from that center pin location on the speaker power socket connector with the other end soldered to the point between C713 and F701 just as you instructed.

Needless to say, I still hacked off L702 just like you instructed, but I desoldered and removed the original 110v AC power socket completely so as to prevent anyone bringing house current to this monitor and now I have ample room to route my lamp cord with its mini-circuit board containing the correct power socket for the Dell laptop external power supply. That cord is about 6 feet long, providing a decent length for ease of external plugging an unplugging of the external power supply--no need to reach underneath the monitor to do it (often without the ability to see where to plug it in and out.)

The original speaker power socket is now available for use, however I do not know if it will work properly after this modification, so I just put a piece of electrical tape over it to prevent anyone from trying to use it. I also generously wrapped my mini-curcuit board containing the laptop power socket with electrical tape to protect it from abuse and to provide a decent way of handling it when plugging the external power supply as needed.

In this way, should the external laptop power supply go south, just toss it and plug a different one in.

Thanks for pointing us in this direction to get our monitors back up and running with little or no cost. This makes a big difference considering the cost of these animals when we bought them. This particular model still has a tremendous value for those of us who understand its format and utilize its potential--if we can find ways to keep them going.

I will be ordering a new Dell U3011 on Tuesday of next week, a similar [16:10] format, but 1/3 wider and 1/3 higher (2560 X 1600) for $1220.00 (w/5-year warranty) directly from Dell. We can never have too many of these excellent monitors.

Thanks for your help on this, and I expect that you will be helping many others in the future with this useful, practical information.