Dell 2407WFPb LCD monitor dead

[sean5302]

My beloved Dell 2407WFPb RevA00 has died.

I've stripped out the 4 boards and am missing any obvious fault. I can't see bulging caps, burnt wires or components.

I've checked many fuses but may be missing something. I cannot light the mains power on led on the switch panel, although there are many voltages around the power supply board. I don't know much about switch mode power supplies.

The fuses I've checked as Ok are these. I seek help, please. Are there more fuses lurking or am I on the wrong track?

All help greatly welcomed. I've searched the forum and can't see what I need.

Fuses checked:
Inverter board F1, F2, F101.
PSU F601, F701
Logic board F9
USB board F801, F802, F803, F804.

My problem started with the power button falling off the monitor ( well known fault) and I had to use a pen nib to switch it on. Now, all is dead.
This monitor cost me £430 in 2009 and I like its style, its fine pitch and its size. I'd love to fix it, if you can help.

[sean5302]

Re: Dell 2407WFPb LCD monitor dead

Just thinking about what I've written:

1. I need to research switch mode power supplies.
2. I'm wondering whether I've broken something on the front power switch. This is just a button switch on a ribbon cable. It has an LED which should light when the power is on. Anyone know what voltage this would use? I'm guessing 5V DC
3. How would I get a circuit diagram for my monitor? The Dell site doesn't show anything.

[selldoor]

Re: Dell 2407WFPb LCD monitor dead

Hi - if you have been a member since 2006 you should know the drill. We need pictures. Fronts and backs of the boards clear enough to read the numbers. and not obscured by flash, posted using the manage attachments and sized accordingly. I see you are in the uk so another light day should be along sometime in the next month .
Dell schematics are difficult to find so that makes the pics a necessity.

A close up of the switch ribbon where it connects to the board may be useful. If it is only a switch perhaps you can try a jumper across where it connects?

Did it come with a 3 year warranty? still valid?

Just watched this http://www.youtube.com/watch?v=WsFQj...der&playnext=1
some guy fixing his on off button and see its more than just a button on a ribbon.
So perhaps close up pics of the button board will help rather than the ribbon connector.

[sean5302]

Re: Dell 2407WFPb LCD monitor dead

Thank you.
Yes, the Youtube video is of the same monitor. I'll post some pics today.
The ribbon cable has 18 wires which push into a clamp connector. A poor arrangement as I cannot readily check that each wire has a good connection. It has a clasp which turns through 90 degrees to lock the ribbon into the female connection on the logic board.
There are 6 LEDs and 6 button switches on the bit of circuit board containing the ribbon cable.
I've been doing some continuity checks with my test meter to try and see which wires connect to which switch and which LED on the ribbon cable. I'm trying to see whether it's this ribbon cable board that is not switching and, now you've prompted me, whether the connection to the logic board is OK.
I'll post pics later.

[sean5302]

Re: Dell 2407WFPb LCD monitor dead

Pics

[sean5302]

Re: Dell 2407WFPb LCD monitor dead

A few more.

These are of the logic board connector for the ribbon cable.

[jetadm123]

Re: Dell 2407WFPb LCD monitor dead

There have been quite a few problems with this model and very few solutions. The link below is fairly long, but may help you. If you have the same board then post #77 may help. Somewhere in that thread is a link to the schematic. And some enterprising member bypassed a portion of the power supply to get it working. The thread is well worth reading.

https://www.badcaps.net/forum/showth...light=2407WFPb

[sean5302]

Re: Dell 2407WFPb LCD monitor dead

Thank you.

I have read through that thread, which mostly concerns the power supply.

I'm hopeful that my problem may just be on this ribbon cable and switch pcb.

A real shame that circuit diagrams and general info isn't available.

I really don't like the construction of the lead, in the way that it attaches to the pcb holding the switches. It's glorified Sellotape, containing 18 "wires" of printed aluminium, just wrapped over the pcb. Who knows whether there is good conductivity?

[selldoor]

Re: Dell 2407WFPb LCD monitor dead

Id start at the switch. Multimeter set to ohms on both switch terminals then press the switch (Yes you need three hands) anything? next Multimeter on ohms one lead on a switch terminal then gently drag the other lead across the terminals on the switchboard end of the ribbon and note which 'wire' it is. Repeat with the other switch terminal. Check the continuity over the ribbon connector you can count across the other end to locate the switch wires. If the cable is good and the switch works then we can concentrate on the PS board end.
You can of course do the whole thing in one go from the switch terminal to the PSBoard end of the ribbon.

At least your connector has the locking strip I have a monitor where there is ribbon from the PSU to the logic board and the lock strip broke. The number of these that break you'd think someone would sell them? Im working on different means of jamming the ribbon into the socket.