Dell 2407WFPb Monitor - Bad Cap

[Misterkeeks]

Re: Dell 2407WFPb Monitor - Bad Cap

Has anyone got this mod to work on the 2405? I tried this mod with a 19V 4A power supply and still no power???

I too would like to know this. Considering trying it, seems easier than troubleshooting.

[budm]

Re: Dell 2407WFPb Monitor - Bad Cap

The reason it does not work may due to the sub-power supply board has the problems, there are buck regulator circuits that convert the 19v to lower voltages that you need to check.
http://s807.photobucket.com/user/bud...?sort=3&page=1

[braxton]

Re: Dell 2407WFPb Monitor - Bad Cap

my 2405 seems to be in standby mode and does not switch over to "on".
Is there a way to bypass the on-off switch or test it at the board?

[danfisch]

Re: Dell 2407WFPb Monitor - Bad Cap

Are the PSU boards for the 2405 and 2407 boards interchangeable? There seem to be a lot of 2407 boards floating around on ebay / taobao, whilst the 2405's are a bit thin on the ground. The connectors mark CN701 (to logic board) and CN702 (to inverter) look identical in terms of dimensions and wiring colours.

[aschi-ch]

Re: Dell 2407WFPb Monitor - Bad Cap

I am currently working on a Power-Supply of a 2407WFPb.
Trough the help of you in this awesome Forum, i was able to find replacement-Parts for all dead components on my board, with exception of one:
On my board, C626 is dead as well. Does anyone know, what capacity C626 is?
Would be great to have more information on that.

btw:
If anyone needs more inforamtion about this board:
I have drawan the complete scematic of that board (currently only by hand as a draft) by following the traces and mesaunring the components.
Now i am adding all known information of all the Parts (Ratings, values, replacement-parts etc.)

[selldoor]

Re: Dell 2407WFPb Monitor - Bad Cap

Looks like this is a list of caps (IF YOUR board is the same) so you can work out
which it is by elimination

https://www.badcaps.net/forum/showpo...2&postcount=33

[aschi-ch]

Re: Dell 2407WFPb Monitor - Bad Cap

Thank you.
Yes it is the same board, but unfortunately there are only the Electrolytic caps listed.
C626 is an SMD ceramic cap.

[selldoor]

Re: Dell 2407WFPb Monitor - Bad Cap

Sorry I did try to find a pic but couldnt see one.
Re there no markings on it - The physical size is also a clue.
If you have made out a schematic do you already know the voltage?

[aschi-ch]

Re: Dell 2407WFPb Monitor - Bad Cap

Yes, ok.
No, unfortunately there are no markings.
It is a standard SMD case, probably 0805 size.
Voltage would be verry low, this cap goes from Pin 4 of the L6561 to Ground.
Pin 4 is the current-feedback-voltage, measured by the famous R670, which is 0.22Ohms.
I would assume that this cap is around ~10nf, it is just to filter the current-feedback.
On the Typical Application Circutis in the datasheet of the L6561, there is no capacitor in that position,
maybe it works even without...

[selldoor]

Re: Dell 2407WFPb Monitor - Bad Cap

I cant find any reference to it as being faulty but on this russian site
http://monitor.espec.ws/section33/post1216836.html

there is a clear picture of it and is is on their wiring diagram.

If it doesnt work without it C628 looks to be the same size and if you have any facility to measure that, perhaps try one the same value.

Unless anyone comes up with a definitive reply.

[aschi-ch]

Re: Dell 2407WFPb Monitor - Bad Cap

I did not find that russian site so far - thanks!
On my board, C628 is a fair bit 'higher' (or thicker) than (what remained of) c626.
Anyway i measured C628 - it's 1uF.

R669 and C626 form an RC-Lowpass for the current-feedback,
currently i don't know the switching-frequency, but 1microfarad seems to be to much:
R669 is 1k, so the filter has a Frequency of 195Hz, which i think is to low, since the switching-frequency is probably somewhere around 10kHz.
I think i will try with ~1-10nF (159kHz - 15.9kHz).

In the meantime i found the Application-Note AN966 from ST.
There i can find one circuit example, where they have a filter in the feedback-path.
There they have 330Ohms and 1nF Capacitor.

You will get a feedback when i replaced all the failed parts, but i have to order them first.
And befor i can order, i have to finish the BOM of another Project, because i want to order all parts together.
So it could take some time till i have any feedback.

[selldoor]

Re: Dell 2407WFPb Monitor - Bad Cap

Ok - Good luck
Its always useful to report back as it may help others in the future.

[dogletico]

Re: Dell 2407WFPb Monitor - Bad Cap

Hello friends.
Won by a monitor 2407WFPb is defective and friend who gave me could not waste time on concert.
Well, ask experts to help this wonderful Forum.
Here is what I noticed in the defect:
Perfect operation, image and fully operational controls, but after 30 minutes, she literally "LOCK". Turns off the power and turns the power on and it starts normally and back to work for another period.
I opened the monitor and visually saw no fault in the components.
I suspect there might be some problem with the "Firmware".
I leave here so this case to analyze.
Hugs.
Ps: Sorry for my English, I'm using a translator.

[selldoor]

Re: Dell 2407WFPb Monitor - Bad Cap

This is not going to be easy!
Can you post good clear pictures of your boards.
When it "locks" do you mean
1 picture stays on
2 screen goes blank power led stays on
3 screen goes blank power led goes off
4 screen goes white.

[dogletico]

Re: Dell 2407WFPb Monitor - Bad Cap

This is not going to be easy!
Can you post good clear pictures of your boards.
When it "locks" do you mean
1 picture stays on
2 screen goes blank power led stays on
3 screen goes blank power led goes off
4 screen goes white.

OK.
On the PC (VGA), after about 30 minutes, the screen goes black, the LED on and dead controls.
Connected to a satellite receiver (TV) (VIDEO) after about 30 minutes, the screen is with mixed colors and illuminated LED controls and dead.
Turning off the power on again and everything back to normal until locked again.
Post photos later.
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?

[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.

[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.

[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?

[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