Dell 2007WFP Won't Power On

[retiredcaps]

Re: Dell 2007WFP Won't Power On

I"m having a problem with my monitor, came home from work one day, try to turn the unit on but it didn't, I'm not even getting the pwr button LED light (orange or green)

First, those are excellent clear focused pictures. The composition is excellent showing both sides and the relationship between boards. I wish more people would provide such great pics.

Second, I have this exact same monitor taken apart waiting repairs/parts.

I found that the logic board (with the Genesis chip) had two bad voltage regulators (right by the connector). U13 and U5 are both shorted.

On the USB board, I found 2 diodes (FD4) shorted.

Lack of proper solder equipment has prevented me from repairing this monitor so far.

PS. I think I got 19V DC if I remember correctly on the power board.

[croket]

Re: Dell 2007WFP Won't Power On

Hello All,

I realize this post has been quiet for about 10 months now and I hope some one out there can still help me out.
I"m having a problem with my monitor, came home from work one day, try to turn the unit on but it didn't, I'm not even getting the pwr button LED light (orange or green)

I do have some electronics knowledge however not a pro.. I've taken it all apart and took some basic readings with my DMM. I've also posted some detailed pictures with my findings.

for starters I"m getting continuity across the fuse on the Power Supply board, at the end of the PS (Power Supply) board I'm getting 18V at each side where CN701 and CN702 are.

This is where I'm confused, the transformer on the PS board doesn't seem like its showing correct reading. look at the close up of the transformer contacts, I've edited it to reflect what my DMM is showing. Other than that I could use any advise or help. Thanks guys!

[chad720]

Re: Dell 2007WFP Won't Power On

thanks PlainBill!
I know I haven´t posted pics and datasheet, but the J598 doesn´t have datesheet (or I can´t find it) and I had already isolated the failure, I only ask for someone that has the knowledge or the diagram of the inverter board to tell me with wich voltage is working the zd701, or if someone has a very huge heart an want to isolate the diode and meassure the voltage, it would be very appreciated!! the integrated that controls the board are two TL1451A
the way to measure this is writen on this forum, quoting is kind of isolating the diode, put a 1kohm resistance in serie and a 24V supply over terminals, so the current would be limited by the resistance and with an voltimeter see the drop over the terminals of the diode, this should be te value I´m needing!
Thanks to everyone who could iluminate my path to recover my monitor.
Chad

[PlainBill]

Re: Dell 2007WFP Won't Power On

Hi there! I´m also trying to repair a 2007wfp dell monitor, had replaced a shorted J598 mosfet, and the two diodes S4 62A (with similar FU4007: 1000V, 1A, 75ns) (one of the S4 diodes was shorted) and also the 3A fuse.
But the result is that I still get a short and is caused by the ZD701 (very little zener diode, the only one on the pcb)
Does anybody know of a proper replacement? I can´t get to figure wich voltage is it suposed to work with, guessing for the size that it´s a 1/4W diode.
Thanks for your wisdom!
Chad
PW: I think pcb voltages are 19V and 5V for the usb, but do not know if there´s another/s.

Earlier today I saw this thread. The gentleman provided a good description of the problem, just like you did. He ALSO provided pictures and a datasheet. This changed a 10 or 20 post problem into a simple analysis.

The best solution to your problem is to identify the zener diode. Many SMD components have a two or three character marking code on the device. With that information, identifying it becomes easy.

PlainBill

[chad720]

Re: Dell 2007WFP Won't Power On

Hi there! I´m also trying to repair a 2007wfp dell monitor, had replaced a shorted J598 mosfet, and the two diodes S4 62A (with similar FU4007: 1000V, 1A, 75ns) (one of the S4 diodes was shorted) and also the 3A fuse.
But the result is that I still get a short and is caused by the ZD701 (very little zener diode, the only one on the pcb)
Does anybody know of a proper replacement? I can´t get to figure wich voltage is it suposed to work with, guessing for the size that it´s a 1/4W diode.
Thanks for your wisdom!
Chad
PW: I think pcb voltages are 19V and 5V for the usb, but do not know if there´s another/s.

[jetadm123]

Re: Dell 2007WFP Won't Power On

Other than a dead short, you will not be able to test cap with a DMM. Replace with good quality caps like panasonic FC or FM series from digikey.com.

[core2kid]

Re: Dell 2007WFP Won't Power On

Okay, i'll work on replacing the caps first. Can I test a cap with a multimeter?

I don't want to take apart the other monitor at the moment, my dad needs it every day and if something goes wrong, I'm dead...

[jetadm123]

Re: Dell 2007WFP Won't Power On

One thing you could try is measuring the voltages at the power connector of the usb board. It looks like the pins are labeled 1-6 and 7-12. Try measuring the voltages with the "good" board installed and again with the "bad" one installed. Also, measure voltages while pushing the on/off button on the front panel. Compare the voltage output of the two boards. If you find a major difference, then try to trace what that pin is connected to.


Yes, a cap can be bad. However, since you have no way of testing them, you'd be replacing them based on a "hunch".

[core2kid]

Re: Dell 2007WFP Won't Power On

I have 2 of these monitors, one is my dads and this one was mine. Basically when it went out, I replaced the USB board with one from a known working monitor and it worked fine. That rules out #3 and #4.

About it working, occasionally it'll work but it'll only go as far as to turn on the backlight for a second and then it'll go off. This happens about 5% of the time.

All capacitors aren't bulged out or leaking. Could they still be bad?
What's the inverter transformer?

[retiredcaps]

Re: Dell 2007WFP Won't Power On

See post 45 to test the voltage regulators and diodes.

Are you saying that if you hookup a working computer with your favourite wallpaper that the computer shows the wallpaper for 2 seconds and then go to black?

If yes, you could have

a) bad capacitors
b) bad inverter transformer
3) bad ccfl
4) bad ccfl wiring/soldering

For the all of above, see starting with post #13

https://www.badcaps.net/forum/showthread.php?t=10419

[core2kid]

Re: Dell 2007WFP Won't Power On

Sorry to bring this old thread back to life but I'm still trying to get this monitor back up. I'm using a CRT for now. Any ideas on what may have failed of the USB board?

[core2kid]

Re: Dell 2007WFP Won't Power On

All the fuses read .00 to .02 Ohms, they also show continuity. Could one of the capacitors have failed?

[jetadm123]

Re: Dell 2007WFP Won't Power On

I resoldered that and it didn't work. Any other suggestions?

Try checking the fuses circled below. With power off and your meter set to resistance, place your probes across each fuse. Reading should be around 0 ohms.

[core2kid]

Re: Dell 2007WFP Won't Power On

I resoldered that and it didn't work. Any other suggestions?

[core2kid]

Re: Dell 2007WFP Won't Power On

I tried to reheat most of the solder points, maybe I missed that one. I'll try it tonight and post back.

I can however say that occasionally it'll power on for 2 seconds and then start flashing.

[Ritalin]

Re: Dell 2007WFP Won't Power On

Not that this is the fix, but is that some cold soldiering on the upper left picture of the back side of the power board?

[core2kid]

Re: Dell 2007WFP Won't Power On

Here are some pictures of the board.

[core2kid]

Re: Dell 2007WFP Won't Power On

Sorry for the delay all, I'm still waiting for a good sunny day when I can take pics. I've been hit by the east coast storm and I haven't had a good sunny day yet, just dull days :/
I'm hoping to have pics for you tomorrow.

[retiredcaps]

Re: Dell 2007WFP Won't Power On

I don't have any idea where to start to even look for the voltage regulators.

How do I check them with a digital multimeter?

Here's some pics of my board.

1) Voltage regulators (U designation) can be bad. They can be shorted or output the incorrect voltage. The test described below only tests the former.

If you have a manual range multimeter, set it to 200 ohms (two hundred). You can test voltage regulators "in circuit" for shorts by (power off and unplugged)

a) black on pin 1- red on pin 2 - record ohms
b) black on pin 1- red on pin 3 - record ohms
c) black on pin 2- red on pin 3 - record ohms

If any ohm reading is less than 30 ohm you might have shorted voltage regulator. Remove from circuit and repeat the tests to verify.

2) To test a diode in circuit,

a) put your multimeter in diode test mode
b) put your black lead on one side and the red lead on the other - record reading
c) reverse the leads - recording reading

A good diode should read 0.4V to 0.7V in one direction and 0L in the other. If you get a reading in both directions, you will have to desolder one leg and retest to verify.

3) PLEASE follow the instructions in PlainBill's signature on how to post pictures so they are posted here and please don't post inline.

[core2kid]

Re: Dell 2007WFP Won't Power On

Sure thing, I'll do it tomorrow afternoon after college. Thanks again for helping me out!