Dell 2407WFPb Monitor - Bad Cap

[terry]

Re: Dell 2407WFPb Monitor - Bad Cap

330 volts DC on the main cap

[selldoor]

Re: Dell 2407WFPb Monitor - Bad Cap

OK - sorry I have been a bit busy - I will have another look through the thread see if I can
come up with anything other than a bypass. I think somewhere in here budm set out where he traced the voltages to.

Do you have the usb board connected when testing?

[terry]

Re: Dell 2407WFPb Monitor - Bad Cap

Yes the USB board was connected when testing.

[grglj]

Re: Dell 2407WFPb Monitor - Bad Cap

Hi, I'm one of dead Dell2407WFPb owners that found this thread encourageing for repair attempt. So after studying whole thread I decided to try and I replaced following components:
C601 NCP1200D
IC651 L6561D
ZD601 15V 0.5W Zener diode
R669 1k
Q651 STP10NK60ZFPC Zener protected N-channel MOSFET
C605 120uF/450V

After powering up it was nice blue logo on the screen and I was happy for a while, but
after few minutes it start smoking and switched off.
By investigation I found F601 fuse blown and R603 visibly burned, and after replacing both I powered it again naked so that I can look at the R603. Now with powering up I still have nice picture on the screen and again after few minutes R603 start with smoking so I immediately switch it off before fuse blow or some more damage (tried few times). I think I'm close to fixing it because it has nice picture when started probably output voltages on the power supply are correct , but for some reason R603 is overheating. Any idea from experienced people? I'm not, so I joined this thread to ask some help. Please

[dthoang]

Re: Dell 2407WFPb Monitor - Bad Cap

My 2407 died yesterday and I found a leaking C605, a shorted Q651, and a blown fuse. I found this thread and went ahead and ordered a STP10NK60ZFP and all replacement electrolytic caps from Digi-Key. I tested all diodes and visually inspected the SMD parts and found no other obviously blown part.

Then I desoldered Q651 and was surprised to find that the part number is K3502. Digi-Key does not stock this part and after some research found that the only difference between the K3502 and STP10NK60ZFP is that the latter contains ESD protection diodes on the gate.

I then did a spec search on DigiKey and found that there are many parts with equivalent electrical specs. I could have gotten a NDF10N60Z for half the price of the STP10NK60ZFP. I thought the would be useful information for my first post.

I'm crossing my fingers that there are no other bad parts. I can't wait to get the 2407 fixed because the colors on the spare LCD I'm using are horrible.

[dthoang]

Re: Dell 2407WFPb Monitor - Bad Cap

My 2407 died yesterday and I found a leaking C605, a shorted Q651, and a blown fuse. I found this thread and went ahead and ordered a STP10NK60ZFP and all replacement electrolytic caps from Digi-Key. I tested all diodes and visually inspected the SMD parts and found no other obviously blown part.

Then I desoldered Q651 and was surprised to find that the part number is K3502. Digi-Key does not stock this part and after some research found that the only difference between the K3502 and STP10NK60ZFP is that the latter contains ESD protection diodes on the gate.

I then did a spec search on DigiKey and found that there are many parts with equivalent electrical specs. I could have gotten a NDF10N60Z for half the price of the STP10NK60ZFP. I thought the would be useful information for my first post.

I'm crossing my fingers that there are no other bad parts. I can't wait to get the 2407 fixed because the colors on the spare LCD I'm using are horrible.

I am happy to confirm that the repair is a success after replacing the fuse, Q651 and C605.

Here are the Digikey part numbers for your reference.

497-5892-5-ND MOSFET N-CH 600V 10A TO220FP
493-6808-ND CAP ALUM 120UF 450V 20% RADIAL
507-1202-ND FUSE FAST 250VAC 4A 5X20
486-1259-ND FUSEHOLDER 25MM PCB 5X20MM

Widen the pin holes for the fuse with a 1/16" drill bit and the fuse holder will fit right in.

I will now replace the other electrolytic caps for insurance.

[pkanar]

Re: Dell 2407WFPb Monitor - Bad Cap

Since I never found a decent circuit diagram, I am posting what I drew after tracing my board. Just added a sprinkling of component specs, and voila -- an unofficial repair manual, for everyone's reference!

[pkanar]

Re: Dell 2407WFPb Monitor - Bad Cap

@grglj: If R603 is overheating, your NCP1200 is internally damaged at the dynamic self-supply stage. What is the resistance measured from pin 8 down to pin 4?

How it was damaged, I cannot guess. Did you overheat it while soldering? That would be the easy possibility.

[BastiaanNaber]

Re: Dell 2407WFPb Monitor - Bad Cap

Last week my wives Dell 2407WFBp went boom. I opened the monitor and found that the power board showed some damage. Attached is a picture. Visually the big CAP shows damage and the R670 is damaged. I have found your nice forum and I am looking for a bit of help.

From what I have read there are two ways to proceed. The first is to try to replace a number of components and the second seem to be to use the speaker port for power. I haven't found many posts that where successful with replacing parts. What is your advice for me? Should I try and replace parts or bypass the power board with the speaker port? What power supply should I connect to the speaker port to get it working?

Thanks in advance!

[lexwalker]

Re: Dell 2407WFPb Monitor - Bad Cap

Last week my wives Dell 2407WFBp went boom. I opened the monitor and found that the power board showed some damage. Attached is a picture. Visually the big CAP shows damage and the R670 is damaged. I have found your nice forum and I am looking for a bit of help.

From what I have read there are two ways to proceed. The first is to try to replace a number of components and the second seem to be to use the speaker port for power. I haven't found many posts that where successful with replacing parts. What is your advice for me? Should I try and replace parts or bypass the power board with the speaker port? What power supply should I connect to the speaker port to get it working?

Looks like Rsense there, 0.22 Ohms with 5% tolerance and 2W at least. Its not common to see catastrophic failures like those, including that main smoothing/filter capacitor. See my previous post here: Dell lcd E173Fpf no power -> Post #12 and you should get some idea of the components that are most likely to be damaged or failed, such as the MOSFET, some diodes, some resistors, some other capacitors (particularly the ceramics) and the PWM I.C. And yes, that one is also a big Dell monitor...

[pkanar]

Re: Dell 2407WFPb Monitor - Bad Cap

@BastiaanNaber: Your failure mode is typical. C605 disconnects, takes out Q651, R670, F601 and a number of other things which vary from case to case, including IC651, IC601, R669, ZD601, Q602. There have been quite a few successful component replacements, all involving replacement of IC's. I personally decided against doing the bypass, as I was not sure where to find an external 19V, 110W power supply offering the accuracy of voltage regulation comparable this board, low noise, low heat, and PFC. But, in principle, if you have such a supply, the bypass is a much easier job than resoldering tiny surface-mounted components.

[pkanar]

Re: Dell 2407WFPb Monitor - Bad Cap

@BastiaanNaber: You have a third option, search for 4H.L2K02.A01 on Taobao and buy a working power board through a reship agent such as Taobaofocus. You would still want to replace the C605 on that, even if it were brand-new.

[Venomhatch]

Re: Dell 2407WFPb Monitor - Bad Cap

Well I am joining this thread as well to say I have one of these monitors that encountered the same main cap with the same issue on one of the poles. Now I have ordered my replacement for that. But I have noticed that there is one cap on the video input board I would like your opinion on (bad or not bad?) The Cap is a 35v 220uf 105c. I have attached it here:

[jetadm123]

Re: Dell 2407WFPb Monitor - Bad Cap

Looks more like red ink from a marker. Leakage from a cap is brown in color.

[Venomhatch]

Re: Dell 2407WFPb Monitor - Bad Cap

Looks more like red ink from a marker. Leakage from a cap is brown in color.

It is coming from the edges of the top leaking inwards to the middle. I also thought it was just marker, and it isn't bulging. But I also never have seen marker look like a powderish substance.

[retiredcaps]

Re: Dell 2407WFPb Monitor - Bad Cap

But I also never have seen marker look like a powderish substance.

If in doubt, replace it since caps are relatively cheap (probably 50 cents).

[chazza]

Re: Dell 2407WFPb Monitor - Bad Cap

Thank you. Fantastic advice. Just repaired my monitor with this mod using a spare laptop power supply. Saved a lot of time and money.
All the best
Chazza

[macjedimatt]

Re: Dell 2407WFPb Monitor - Bad Cap

My monitor also failed, I tried using the powersupply trick with a Dell PA-9 adapter. The power adaptor's light goes out when I connect power to it. It looks like the transformer(?) near the top of the board is damaged. The markings under the heat pad are: 1J.20289.001 LTSJ 0621. Anyone know where I can get a replacement? I tried searching digikey but there are way too many options.

[pkanar]

Re: Dell 2407WFPb Monitor - Bad Cap

@macjedimatt: You are reporting what appears to be a new mode of failure. May I ask on what evidence do you conclude that T601 is damaged? And there is no corrosion where the + terminal enters the body of C605?

[macjedimatt]

Re: Dell 2407WFPb Monitor - Bad Cap

No. This was the same failure. After successfully fixing 2 of these, for some reason I thought it would be a good idea to cut the small wires on it. I thought it was connecting to the AC side of the board. As soon as I did it, I realized what that part was for The damage is a little beyond what I can manage to repair safely. It doesn't look like something I can find easily without more information, which I haven't been able to get. I suppose it is just as well. This panel has a scratch on it and the stand is missing.