Dell 2407WFPb Monitor - Bad Cap

[AquaSonic]

Re: Dell 2407WFPb Monitor - Bad Cap

Hello! I have a question :

I have the 2405fpw, the 120uf 450v died, the classic things happened blah blah. Now:

If i do the audio out jack mod, are the IC601 and 651 required? They were both shorted and i removed them. I had to do also a buck converter bypass in the logic board (Since it failed and the D19 resistor had blown, i found it easier just to replace it with a DC/DC converter) Now i get 5V in the Logic board L1 without any shorts, however the monitor still dead. I tried to trace where the 5V goes, but i couldn't :/ Any suggestions on what to check?

Also, what should the measurements be for the PSU - Logic Board Connector?

Thanks

[pkanar]

Re: Dell 2407WFPb Monitor - Bad Cap

@Andrew_LB: when I repaired mine, I would have preferred to buy a full new power supply board, and update the C605 on that. But at the time, there weren't any for sale on Taobao or eBay. Now there are, and they look like exact OEM clones. I ended up doing it the hard way: swapping circuit elements. It worked, but not worth the savings.

If you had read through this thread in more detail, you would have saved that new fuse. When the big cap dies, it always takes out one or both IC's, and more.

So, what blew? Did the C605 blow?

[Andrew LB]

Re: Dell 2407WFPb Monitor - Bad Cap

If the output of the IC (which is more likely to be damaged) that drives the Gate has stuck HIGH output instead of switching on and off, the MOSFET will be fully on, basicaly shorted the main B+ to primary circuit ground, it is always good idea to replace the IC and the MOSFET at the same time.

Doh!!! Time to order a new IC.

[wobbin]

Re: Dell 2407WFPb Monitor - Bad Cap

Yes Quantumraj, that's the one. Good luck !

Cheers
Robin

[budm]

Re: Dell 2407WFPb Monitor - Bad Cap

If the output of the IC (which is more likely to be damaged) that drives the Gate has stuck HIGH output instead of switching on and off, the MOSFET will be fully on, basicaly shorted the main B+ to primary circuit ground, it is always good idea to replace the IC and the MOSFET at the same time.

[Andrew LB]

Re: Dell 2407WFPb Monitor - Bad Cap

Well.... I replaced the big cap, q651 MOSFET, and burnt out R670 resistor... Put things back together just enough so I can apply the power and when I did... I saw a quick flash from the ceramic fuse.

Any thoughts?

Edit:

Hmm... Did the fuse blow because the cap was empty? From my experience with powerful car audio amplifiers I recall that when first applying power the fuse would blow because of that sudden power draw to fill the amos built in capacitors or if I was using a separate stiffening capacitor. To avoid this on first hookup we'd ground the amp and put a resistor between the hot terminal and the power cable. I know this far less power with these caps but wouldn't the same principal apply since the fuse is correspondingly small?

Thanks!

[Andrew LB]

Re: Dell 2407WFPb Monitor - Bad Cap

Ok.. here are some photos of the damage. I've already removed the big cap and R670, and installed a Rubycon 450v 120uF capacitor. I just did some testing and I believe Q651 is bad, and now that can see the IC's up close, it looks like IC651 may be bad. Not sure on that though.

But I came here to get your guys opinion considering I'm very novice at diagnosing problems with circuit boards.

I found "new" power boards for the 2407wfpb on ebay, shipped from Hong Kong for only $24.99, which isn't a bad price. From my understanding though, they come with Elite caps, which should be replaced on day 1.

As a backup plan I came across a laptop power brick which is 19.5v (actually reads 20v on my meter), 5.13A 90watts. Spec wise, it seems perfect for modding the 2.5mm jack on the power board and going that route. I'd rather not risk killing this screen though.

[Andrew LB]

Re: Dell 2407WFPb Monitor - Bad Cap

All failures of the big cap seem to be the same: no evidence of leaking, but corrosion and eventual disconnection where + terminal enters the body.

Mine went "ssssssst... BANG!". Scared me half to death the other night. I'd say it was as loud as a .22 cal "SHORT" being fired. It happened while bringing the 2407wfp out of standby mode. The big cap is blown, so is R370. Other than that no visible damage.

lemme go take some photos. brb.,

[quantumraj]

Re: Dell 2407WFPb Monitor - Bad Cap

Thanks. will Try it out. Just to make sure, the "Signals" board (is it the C board or the inverter A as in picture.)

[wobbin]

Re: Dell 2407WFPb Monitor - Bad Cap

I had this problem with my 2407 - in my case I swapped the signals pcb in the end and it has been fine since <touches wood quickly>

I tried recapping the pcb before I replaced it but there was no change in behaviour.

HTH

[quantumraj]

Dell 2407WFPb Monitor - Unresponsive

issue with 2407 where the monitor works for 1-2 hours. then unresponsive, no display (can see the backlight working). Buttons don't function, unplugging/plugging power on resolves it but it comes back faster next time. there is also flicker once in a while. Opened the monitor and looked at all PCB's for bad caps (all look nice and no bulges or residue of any kind), nothing that I can tell visually. Will post a few pictures in case I missed something. Given the symptoms which PCB should I focus on, power or inverter.
Thanks

[supertox]

Re: Dell 2407WFPb Monitor - Bad Cap

I found a schematic diagram for the power board (4H.L2K02.A11) of the Dell 2407WFP. The document is naturally for the BenQ FP241VW.

The original document with an ugly background can be found here.

[pantarhei]

Re: Dell 2407WFPb Monitor - Bad Cap

I have 6 Dell 2407s I bought as a job lot. All the PSUs have failed. I searched on eBay UK and didn't find any cheap ones. When I searched on eBay.com I found several new 2407 PSUs around $25 inc. shipping to the UK. I made an offer for 6 of them and won them. How good they will be I don't know as they haven't arrived yet, I expect them in about 4 weeks. I may have to pay import duty. I would think they'll work fine. How good the 120uf 450v cap will be is questionable. I also found some 100uf @ 450v caps which were quite cheap which I have also ordered to replace the caps that come on the new PSUs.

Current Item no. for PSU is 131028175844
Current Item no. for 10 caps is 400583064089

I am very, very happy, the replacement power supply works.
I ordered a power supply for USD 29.99 + USD 10 shipment on ebay from user waxue-1990. The shipment arrived after 2 weeks and 5 days from china to Switzerland, that is AFAP. I hope it will last for some time. I think it has the same crappy capacitors.

[selldoor]

Re: Dell 2407WFPb Monitor - Bad Cap

Wow! well done Schematic should be a great help for the future 90k people looking at this thread.

[aschi-ch]

Re: Dell 2407WFPb Monitor - Bad Cap

We have a Winner:
My 2407WFP is working again.

The for the cap C626 i used 1nF, Farnell 1856532,
seems to work fine.

Still working on the Schematics, have it but need to draw them better.
Will post when ready.

Thank you for you help!

[TiW]

Re: Dell 2407WFPb Monitor - Bad Cap

At the moment there are some offers for power supplies on ebay. The power supplies are advertised as new with a price tag from USD 20 to USD 60 and shipping cost from USD 10 to USD 30. Anybody had success with a power supply from china?

I have 6 Dell 2407s I bought as a job lot. All the PSUs have failed. I searched on eBay UK and didn't find any cheap ones. When I searched on eBay.com I found several new 2407 PSUs around $25 inc. shipping to the UK. I made an offer for 6 of them and won them. How good they will be I don't know as they haven't arrived yet, I expect them in about 4 weeks. I may have to pay import duty. I would think they'll work fine. How good the 120uf 450v cap will be is questionable. I also found some 100uf @ 450v caps which were quite cheap which I have also ordered to replace the caps that come on the new PSUs.

Current Item no. for PSU is 131028175844
Current Item no. for 10 caps is 400583064089

[pantarhei]

Re: Dell 2407WFPb Monitor - Bad Cap

My Dell 2407 has has the most common problem in this thread:
a oxidized capacitor C605, burned R670, broken IC651 (like it exploded), some other semiconductors have 0 resistance ...

Is there evidence that this type of defect is "planned obsolescence or built-in obsolescence"? I assume the capacitor C605 is a special type to reduce the lifetime of this monitor to less than 6-8 years.

At the moment there are some offers for power supplies on ebay. The power supplies are advertised as new with a price tag from USD 20 to USD 60 and shipping cost from USD 10 to USD 30. Anybody had success with a power supply from china?

[dogletico]

Re: Dell 2407WFPb Monitor - Bad Cap

Hello to all.
did the tests suggested by selldoor friend and really my problem and heating.
It now remains to know where to begin searching for the cause of this warming.
Any county are welcome.
Grateful.

[dogletico]

Re: Dell 2407WFPb Monitor - Bad Cap

"On the PC (VGA), after about 30 minutes, the screen goes black, the LED on and dead controls."

Can you still see anything on the screen - perhaps shining a flashlight on it?

If you switch it on and heat the boards with a hairdryer does it turn off any quicker?

If you keep it cool with a fan does it stay on any longer?

I'll try these procedures that you suggested, first with the dryer and then with the fan.
I'll post the results.
Grateful.

[selldoor]

Re: Dell 2407WFPb Monitor - Bad Cap

"On the PC (VGA), after about 30 minutes, the screen goes black, the LED on and dead controls."

Can you still see anything on the screen - perhaps shining a flashlight on it?

If you switch it on and heat the boards with a hairdryer does it turn off any quicker?

If you keep it cool with a fan does it stay on any longer?