Re: Dell 2405fpw - Backlight problem



[B]From pin 3 to pin 5[/B] (200 M Ohms setting)

Q106 – 1.1 M ohms
Q105 – 1.1 M ohms
Q6 – 1.0 M ohms (tested many times)
Q7 – 1.1 M ohms
Q4 – 1.1 M ohms
Q5 – 1.1 M ohms



I tested the SMD ceramic capacitors. I can do simple low capacitance tests on multi-meter .I can test using 100u, 2u, 200n, 20n.

All of the following capacitors are located next to the mosfets which I measured in the previous post.

[B]Capacitance...

Re: Dell 2405fpw - Backlight problem

I decided to reattempt measuring the resistance using the Ohms function on the multimeter since the diode function try was wrong.

I could only get a reading if I set the multimeter to 200M Ohms which was probably why I ignored it in my first try. I'm not entirely sure I've used the correct setting ?

From pin 1 to pin 5 (200 M Ohms setting)

Q106 - 1.2 M ohms
Q105 - 1.2 M ohms
Q6 - 1.2 M ohms
Q7 - 1.2 M ohms
Q4 - 1.2 M ohms
Q5 - 1.2 M ohms

It seems like...

Re: Dell 2405fpw - Backlight problem




Hi, I'm unsure if I've numbered the pins correctly. I assumed the pin number starts with the dot/indent. The 5,6,7,8 pins are all linked according to my continuity test. I've attached my version of the pin numbering system just in case it is wrong.

From pin 1 to pin 5 (diode/continuity test mode)

Mosfet model - 4512C AA5MV

Q106 - 531 ohms
Q105 - 532 ohms
Q6 - 532 ohms
Q7 - 533 ohms
Q4 - 532 ohms
Q5 - 530 ohms

Thanks for the help...

Re: Dell 2405fpw - Backlight problem

Hi,

I've just replaced the fuse and after I switched the screen on it blew again.

I clean the board by spraying some isopropyl alcohol and found a dirty looking component C31 which I assume is some kind of surface capacitor ? It looked like it had been soldiered by myself (messy) and had some yellow residue beside it. I'm not fully sure if it has exploded or it's just dirt.

I've only got a cheap £30 multimeter so it's unable to test capacitors. Is it possible to test capacitors with a basic multimeter ?...

Re: Dell 2405fpw - Backlight problem

Glad the data helped you out. If you need more readings for confirmation, I'll be happy to post it once I get my fuses delivered.

Re: Dell 2405fpw - Backlight problem

Thank you Selldoor, I've removed the fuse and yes, it's broken. I've googled SMDs and and yes the "k" stands for 1.5 amp.

A even bigger thank you goes for the CPC free delivery link. That will save me a fair amount of money since I usually order components from RS.

Fingers crossed, this solves the issue unless the power supply has blown something else.

Thanks once again for your guidance

Hi,

I have casually been reading posts on this site for about a year hoping that “one day” I'll have enough knowledge to fix my Dell 2405fpw. The monitor turns on (power button lights) but nothing shows up until I use a flash-light and see that the “please connect input“ default error screen is bouncing around. So the back-light needs more power.

I was hoping it was the usual capacitor problem but after changing all of them the monitor would only have a brief flash. I would also hear a click/buzz sound which sounded like someone was flicking a switch on and...