DELL 2007wfp - 2 Secs to black w/flickering

[Armandorf]

Re: DELL 2007wfp - 2 Secs to black w/flickering

Im moving my stuff to other place so till tuesday im stuck.

later I will desolder the new transformer

at first I thought that a faulty ccfll overcharged the transformer with that ccfl. but they glow. probably is the inverter only.

finding an inverter board complete can be the solution.

[selldoor]

Re: DELL 2007wfp - 2 Secs to black w/flickering

Unless your meter is broken there is no such thing as "No Reading".

I think that the 1500 resistance would trigger a shutdown but it may depend on the circuitry - the primary also seems different.

Perhaps update your profile with country and voltage.Someone near you may
have a spare?

[Mac Nut]

Re: DELL 2007wfp - 2 Secs to black w/flickering

I have been doing some searching using google and I'm not finding any transformers that mach the 4001r714050 exactly, should this 4001K do the trick? Or is the 15K resistance enough different that it would cause problems?

[Mac Nut]

Re: DELL 2007wfp - 2 Secs to black w/flickering

3rd transf

1-8 resistance: 1.040 K
4-5 resistance: 52.3 K(200K scale)

Interesting... I have a 2007wfpb that's doing the same thing. ...and the same transformer is bad. I wonder if there was some sort of error in the design or if this is purely a chance happening?

T801:
1-8:1076Ω
4-5:1089Ω

T802:
1-8:1089Ω
4-5:1095Ω

T803:
1-8:No reading
4-5:1078Ω

[Armandorf]

Re: DELL 2007wfp - 2 Secs to black w/flickering

yes the damage is only in the cover, i did it when i removed the old transformer that had an open winding, i dont have a good transformer out of the board, but i can desolder one of the other two original transformers.

comparing readings in the board without desoldering:
1st original 0.03ohm
2nd original(middle)0.04ohm
3st new open, infinite resistance

i believe the originals have 0.8ohm in each winding becuase:

middle pins are joined in the board. i suppose that the board is putting the 2 resistances(p1 to p3 and p2 to p4)in paralel, giving half the original resistance value for each winding)

anyway i think i will be desoldering it to check for sure

[selldoor]

Re: DELL 2007wfp - 2 Secs to black w/flickering

Are you sure it measures as OPEN and not as 0.00. we are only expecting it to be less than 1 ohm so meter should be on ohms20 or less.
What do the primaries on the old one measure
Can you unsolder it again and post pics of the bottom of both the old and new.
align them with the positioning pin at the same end.
I also notice there is some damage to the cap - does it just extend to the outer plastic?

[Armandorf]

Re: DELL 2007wfp - 2 Secs to black w/flickering

4001Rxxxxxxxx is the type i need? i have wasted so many time, at least i ve learned

[budm]

Re: DELL 2007wfp - 2 Secs to black w/flickering

The board that I have here in front of me has two transformers with P/N 4001R702048, the middle transformer has P/N 4001R703038. When you told us the replacement was the surface mounted type, then I kind of suspect that it is not the same transformer as original.

[Armandorf]

Re: DELL 2007wfp - 2 Secs to black w/flickering

i measured p1to p2 and p3 to p4. both readings marks open

i read that the 4001 was the important part of the transformer, i have a wrong transformer? i cant find the exact model en ebay

[retiredcaps]

Re: DELL 2007wfp - 2 Secs to black w/flickering

PS. It would also help if you posted a picture of your new transformer and jumper leads.

[budm]

Re: DELL 2007wfp - 2 Secs to black w/flickering

Thanks retiredcaps for clarifying my question. This transformer has two Primary windings and two secondary high voltage windings. Just want to make sure the new transformer has the same windings as the original one.

[retiredcaps]

Re: DELL 2007wfp - 2 Secs to black w/flickering

what do you mean with low ohm readings? in which pins I should measure?
in the pcb the 2 central pins of each side are joined

Budm is asking you to measure P1 to P2 and P3 to P4. See diagram below. It is not a 4001R, but the 4001K is "close enough".

http://www.lcdparts.net/TransformerD...ProductID=2725

[Armandorf]

Re: DELL 2007wfp - 2 Secs to black w/flickering

what do you mean with low ohm readings? in which pins I should measure?
in the pcb the 2 central pins of each side are joined

[budm]

Re: DELL 2007wfp - 2 Secs to black w/flickering

Your power supply is OK, it is only a single output supply, 19VDC, this 19V is coverted down to lower volltage to run the logic board, the inverter runs off the 19V directly. Your problem is more likely to be in the Inverter board. Does the new transformer 4 middle pins of the transformer all have low Ohm reading?

[Armandorf]

Re: DELL 2007wfp - 2 Secs to black w/flickering

yes, the readings were 1.054K and 1.055K, and the readings in this transformer are equal to the other two.

looking the power supply, i searched for bad diodes or smd transistor shorted(continuity test)
and found something

i have 19.2v dc
an other 3 pins with 3.3v, 0,8v , 0v(it seems 2,5 mV with the tester in 200mV scale)

the last pin has no voltage but it doesnt seem grounded(continuity test with chassis marks open)

posted an edited pic of the solder layer for the voltages in the power supply

where i cand find a diagram for this power supply?
i will be looking for dead voltage regulators in the other boards, i read thats quite common.

[retiredcaps]

Re: DELL 2007wfp - 2 Secs to black w/flickering

yesterday arrived the transformer.

Did you measure the resistance of the new transformer before installing it? If no, what is the measurement?

edit: budm beat me by 2 minutes.

[budm]

Re: DELL 2007wfp - 2 Secs to black w/flickering

You are saying that this replacement transformer has surface mounted pins instead of the through hole pins. Does it have the same part number as the original and did you take any resistance reading to see if it is the same as the original good transformer?

[Armandorf]

Re: DELL 2007wfp - 2 Secs to black w/flickering

yesterday arrived the transformer. it had SMD pins, so i put short wires(ends of used caps or resistences), soldered and mounted the transformer on the inverter.

i tested
but i still have the same problem; it flashes very quickly and i can see the [ No signal OSD] for a fraction of a second

i re checked the 6 ccfl´s with an inverter from a Lg 19'' and they flash once,1 second off, and lit on again, this time with an increasing brightness during the first 3 seconds .finally they still hang on with no noticeable problems.

[Armandorf]

Re: DELL 2007wfp - 2 Secs to black w/flickering

sorry i abandoned this thread for a long long time, thanks for the help, and i hope that this photos and information to be helpful in the future.

i had many issues with my mailing from china ebay, hopefully in 3 weeks will be arriving the little transformer.

if anyone needs a photo of some board of the
monitor i can post it.

[retiredcaps]

Re: DELL 2007wfp - 2 Secs to black w/flickering

what about the tubes, theres a slight blackness in the ends, should they work a couple of years more?

They look okay, but sometimes the return wire (the thinner guage) can become disconnected/charred/frayed. You can't see it because it is inside of the silicon cap end. Replace the transformer first and retest. I expect it will work fine and the caps and the transformers were the only bad things.

im a bit nervous about shopping from ebay to argentina, i will research.

My experience with China based sellers have been mainly positive. They are quick to correct mistakes.

in the logic board, i find the caps slightly bulged, its better leave them as it is, or replace all of them?

Any cap that is slightly bulged is automatically bad. We recommend the standard advice (regulars may skip)

https://www.badcaps.net/forum/showpo...84&postcount=3

edit: If you are talking about the green Lelon caps by the connector on the logic board they look completely flat to me in one angled picture. The caps on the logic board don't undergo the same stress as those on the power board.