Dell 2405FPW blown transformer?

[ucdzombie]

Re: Dell 2405FPW blown transformer?

Anyone?

[ucdzombie]

Re: Dell 2405FPW blown transformer?

OK just some updates. I just ran an ohm test on the 7 bigger capacitors (including the 450v), all of them are dead (although there's no signs of physical damage). The needle on my multimeter went to the right, stayed, and never returned to infinity. So maybe the transformer is OK?

[ucdzombie]

Re: Dell 2405FPW blown transformer?

Just to nitpick when you say "current" you actually mean voltage.
It's a very important distinction to make

https://en.wikipedia.org/wiki/Voltage
https://en.wikipedia.org/wiki/Electric_current

Yes! Thank you for correcting me. Forgive me for my ignorance.:p

[ucdzombie]

Re: Dell 2405FPW blown transformer?

What DCV do you get between the two legs of that large black 450VDC main filter cap?

Hello budm. Thanks for helping me again! The reading of the 450v capacitor is 160 volt. I've attached a picture in case I'm wrong. Initially I test it under the scale of 500v on the multimeter. But since the reading is low, I switched the scale to 250v.

Also I tried testing f702 fuse again. The voltage reading is about 7v. Let me do it again tonight to confirm on this.

As far as the big fuse next to the power connector, I tested it again. The needle on the multimeter barely moved on the lowest scale.

[Per Hansson]

Re: Dell 2405FPW blown transformer?

Just to nitpick when you say "current" you actually mean voltage.
It's a very important distinction to make

https://en.wikipedia.org/wiki/Voltage
https://en.wikipedia.org/wiki/Electric_current

[budm]

Re: Dell 2405FPW blown transformer?

What DCV do you get between the two legs of that large black 450VDC main filter cap?

[ucdzombie]

Hi everyone. I've searched the forum thoroughly about this problem but couldn't find anything similar to my Dell's symptom.

I've repaired this monitor before by replacing two 5v slow blown fuse (F701 and F702) and modified the bad MOSFET on the logic board (under the direction of an electrical engineering professor). I've enjoyed my repair for two years and now it's dead. When power is on there's no response at all, no front LED light, no image.

I'm not an electrical engineer so I can only do a couple of test on the power board. I've attached a picture for you to review. Basically all the fuses have been tested and they're all normal (zero resistance, normal continuity with the multimeter buzz sound). However, when power on, the big fuse next to the power input has no current reading at all, so are the rest of the components. I've not tested the transformer since I don't know how to test the legs. But I'm suspecting that it's a blown transformer?
The only two places that have 120v reading are the power connector and the small resistor behind it. Any help would be much appreciated! Thank you all.