Dell 2407wfp backlight problem

[budm]

Re: Dell 2407wfp backlight problem

Yes, Red probe on the positive leg, black probe on the neagtive leg, be real careful because you will be working on the Hot (LINE) side of the circuits.

[leapius]

Re: Dell 2407wfp backlight problem

ok I rubbered up and found:

340v - stand by
465v - powered on

[budm]

Re: Dell 2407wfp backlight problem

465V! That is way too high, the cap is rated at 450V (in my 2407). Are you sure? The symptom you are having is very strange is that the 19V power supply is OK, the voltage is correct.

[leapius]

Re: Dell 2407wfp backlight problem

Sorry my bad I just check again:

~ 335v - stand by
~ 370v - powered on

They seem to fluctuate maybe +-5v with my tester.

[budm]

Re: Dell 2407wfp backlight problem

I will see how much my fluctuates tonight.

[leapius]

Re: Dell 2407wfp backlight problem

Thanks budm, so a recap:

- solid voltages to inverter board.
- inverter capacitors changed.
- with 3 of the 6 bulbs connected they will come on fully bright (for 2 secs obviously).
- the more bulbs I add in the worse the problem gets.

It seems like when there is more load on the inverter board it just can't strike the bulbs fully and they are dim on the far side. Any ideas what can cause a CCFL bulb to only half light in this situation?

Thanks.

[budm]

Re: Dell 2407wfp backlight problem

Your conclusion is right, some how the inverter just cannot handle all the lamps.

[sebr]

Re: Dell 2407wfp backlight problem

Any progress lately?

[leapius]

Re: Dell 2407wfp backlight problem

Any progress lately?

Well, yes actually. I worked out it was the cermic capacitors on the other side of the transformers on the inverter that were at fault. Unable to replace these due to lack of equipment to identify the capacitor types and resolder such small components I ordered a new inverter from aliexpress, which worked fine. The bulbs light up fully.

The one problem that remains is that after a while the bulbs will go fully bright and are not affected by reducing the the brightness using the controls. This might point to why the original inverter broke down in the first place?

[GoNz0]

Re: Dell 2407wfp backlight problem

Well, yes actually. I worked out it was the cermic capacitors on the other side of the transformers on the inverter that were at fault. Unable to replace these due to lack of equipment to identify the capacitor types and resolder such small components I ordered a new inverter from aliexpress, which worked fine. The bulbs light up fully.

The one problem that remains is that after a while the bulbs will go fully bright and are not affected by reducing the the brightness using the controls. This might point to why the original inverter broke down in the first place?

super necro post but could you guide me to the offenders please?
I have a working one to try and figure out what parts I need so I may be able to take a reading from them when I know ones they are.
Thanks.

[GoNz0]

Re: Dell 2407wfp backlight problem

super necro post but could you guide me to the offenders please?
I have a working one to try and figure out what parts I need so I may be able to take a reading from them when I know ones they are.
Thanks.

I got this out again today and can't for the life of me figure out what parts bad

Did the 3 caps and the suspect on the power board last year get the same results as the OP...