Another Dell 2405 FPW fails

[thomaskuhn]

Hi everyone,

I am new to the board but have been following the saga of Mirage00 and his Dell 2405 FPW display problems:

https://www.badcaps.net/forum/showth...hlight=2405fpw

I too am having a very similar issue. The backlight comes on, the power buttons work, and the source select button is operating, but there is no display. So I began running the procedures you had recommended to Mirage00. I started with testing the voltage on the T-CONN board at the fuse with 0V on both sides and 0.2ohms across it.

I also tested the "torpedo Fuse" and it was 0.1ohms

I then moved on to testing the 4 MOSFETS that were recommended to test:

F53055
Pin 1 - 0V
Pin 2 - 0V
Pin 3 - 0V

FR9024N
Pin 1 - 0V
Pin 2 - 0V
Pin 3 - 0V

H184
Pin 1 - 3.3V
Pin 2 - 0V
Pin 3 - 2.51V

H185
Pin 1 - 0V
Pin 2 - 1.81V
Pin 3 - 3.29V

It is here that my measurements are different from Mirage00's readings. He was getting voltage to these components. I am not. One additional piece of information is that I tested the 10 lead cable that comes over from the power board, and the results are as follows:

Grey - 0V
Purple - 0V
Blue - 0V
Green - 7.33V
Yellow 3.25V
Orange - 0V
Red - 0V
Brown - 2.32V
Black - 3.26V
White - 3.21V

All of these seem extremely low going over to the logic board. Any diagnostic help would be greatly appreciated. I am attaching photos.

Thanks,

Tom

[retiredcaps]

Re: Another Dell 2405 FPW fails

One additional piece of information is that I tested the 10 lead cable that comes over from the power board, and the results are as follows:

Grey - 0V
Purple - 0V
Blue - 0V
Green - 7.33V
Yellow 3.25V
Orange - 0V
Red - 0V
Brown - 2.32V
Black - 3.26V
White - 3.21V

Most power supplies have a 5V standby voltage. 7.33 is a very odd voltage.

Disconnect all the boards from the power board and remeasure those same 10 pins and post your results.

PS. Those are good focused pics.

[thomaskuhn]

Re: Another Dell 2405 FPW fails

Thanks for the compliments on the photos. I have a Lumix LX-5 which is Great for closeup photos.

Here are the readings with nothing connected to the board:

Grey - 0V
Purple - 0V
Blue - 0V
Green - 7.28V
Yellow 0V
Orange - 0V
Red - 0V
Brown - 0V
Black - 0V
White - 0V

[retiredcaps]

Re: Another Dell 2405 FPW fails

Green - 7.28V

1) Another reason for me to hate Dell. From another thread, it looks like 7.3V is their normal standby voltage. Arrggghhh!!!

2) Can we get a picture of the tcon without the shield in front of it?

3) Can you measure the DC voltage on the t-con right hand side connector?

[budm]

Re: Another Dell 2405 FPW fails

Did you read the rest of the link with regarding to shorted Zener and MOSFET, I know it is a long thread. He ends up install a new switching power supply to supply the power to the T-CON board. He was also getting 0V at the T-CON fuse.

[retiredcaps]

Re: Another Dell 2405 FPW fails

Did you read the rest of the link with regarding to shorted Zener and MOSFET, I know it is a long thread.

Geez, when I'm dead tired the last couple of days, I don't remember participating in that thread! I can't believe summer has flown by already.

[thomaskuhn]

Re: Another Dell 2405 FPW fails

Let me see what i can do when i get back from work. I tried to remove the cover to the t-con but it is tricky because the tabs are underneath the main metal "screen cover". Does anyone know how to do it?

I saw about the mosfet and using a 5v power supply. Its funny that i think i have a 5v 3A board just like the person from the previous post. Would i be bypassing any other components that could have been powered from the possibly bad power supply that would still not function?

[budm]

Re: Another Dell 2405 FPW fails

"I started with testing the voltage on the T-CONN board at the fuse with 0V on both sides and 0.2ohms across it."
"I tried to remove the cover to the t-con but it is tricky because the tabs are underneath the main metal "screen cover". Does anyone know how to do it?"

So how did you check the fuse on the T-CON if you did not know how to remove the cover? I am confused.

[thomaskuhn]

Re: Another Dell 2405 FPW fails

Good question...

I took out the screws and could leverage the side up enough to see the fuse (based on another picture) and could get my leads in there to test.

[thomaskuhn]

Re: Another Dell 2405 FPW fails

Ok,

I just got the cover off. To make it easier to put back in without dealing with the flex cable, I ended up trimming the metal a bit.

[thomaskuhn]

Re: Another Dell 2405 FPW fails

Ok,

I just finished rereading the Mirage00's thread again. I looked at the linkthat was posted regarding the blown Q1 and D17 Diode:

http://www.cse.iitb.ac.in/soumen/Sys...2405fpwRepair/

I went and tested those components... Both Blown! Along with the Fuse that missed before on the power supply side.

I guess I will do what everyone else is doing and get a DC to DC converter for powering the T-Con board.

Question, will I need to replace the fuse on the Power supply board (F701 - labeled "5A LF")? If so, what with?

So far I will need to order the DC-DC converter:
https://cdn.badcaps-static.com/pdfs/...4ea943619a.pdf

Anything else I need to replace?

[thomaskuhn]

Re: Another Dell 2405 FPW fails

Ok,

I have temporarily put a wire jumper to replace the fuse. I am trying to look at what the DC-DC converters are hooked to to get their source power. I removed the MOSFET, caps C9 and C8. I did not remove the coil yet. Where is the source coming in?

[thomaskuhn]

Re: Another Dell 2405 FPW fails

Once again i looked at the other thread. He mentioned that he was getting 18v to feed into his dc-dc converter. I just checked a bunch of points in thst area and can not find anything at 18v.

[thomaskuhn]

Re: Another Dell 2405 FPW fails

I have taken another look at the power supply board. I powered it up and checked where I put the temporary jumper to use instead of the Littlefuse 5A fuse. 22V on one side and 0V on the other. Strange. I flipped over the board and quickly found out why. Burned in half. I am not sure when this happened.

I decided to trace where this goes after the fuse. It heads right out of the header and onto the logic board (red Wire) Thats why I was not seeing any voltage on that side. I have since stripped out some of the components similarly to what others have done. I have a good idea of where to connect the Power Trends PT6302A DC-DC converter.

Is there something that I am missing that might have shorted the temp fuse?

[thomaskuhn]

Re: Another Dell 2405 FPW fails

FIXED IT!!! YEAH!!

I finally wired in the DC-DC converter. All voltages look good. Screen running well. I think I burned out the jumper when I still had the MOSFET connectoed to the board.

Here is a photo.

[budm]

Re: Another Dell 2405 FPW fails

Great job, see, you can do it on your own, just have to do some reading and probing.

[JuliaS]

Re: Another Dell 2405 FPW fails

I've got the same problem. The output of the MOSFET in question is 3.3V (below the 5V it should supply), so I suspect that it might still be good. The 47uF and 220uF caps are of Jamicon brand. Do you think doing a complete recap would solve the issue or should I go straight for the 5V DC/DC converter instead?