DELL 2405fpw

[Mirage00]

My Dell 2405fpw stopped displaying anything on the screen. The power goes on and all controls work (front lit green buttons all work). The backlight is working when connected to a computer. I run my finger against the screen and see the white light. The Dell self test menu does not display nor does the On Screen Menu. I have taken off the back cover and can't see any obvious issues with CAPS so I will need to start testing. Does this sound like a LOGIC board issue? Where do I start testing ? Thanks in advance, this is a great forum!!!!

[budm]

Re: DELL 2405fpw

It sounds like the T-CON board (Board is under the metal shield) is not getting the voltage from the main board, or it has blown fuse on the T-CON. You need to check that board.

[Mirage00]

Re: DELL 2405fpw

I just lifted the metal shield enough to test the fuse with the DMM and it was fine. What do I test next?

Also, here are the pics from the panel board

[retiredcaps]

Re: DELL 2405fpw

What is the DC voltage on each side of the fuse with respect to ground? You should have 2 readings.

[Mirage00]

Re: DELL 2405fpw

Not exactly sure how to do that. I have the multimeter set to DCV at 200m and when i touch a ground point (screw hole) on the card and each end of the fuse I get .5 on both sides. Did I do it correctly? BTW this is my DMM I am using

[retiredcaps]

Re: DELL 2405fpw

Not exactly sure how to do that. I have the multimeter set to DCV at 200m and when i touch a ground point (screw hole) on the card and each end of the fuse I get .5 on both sides. Did I do it correctly? BTW this is my DMM I am using

1) You get one retiredcaps' bonus point for a picture of your multimeter. I have never seen the Harbour Freight special in yellow, just red.

2) You want it set on 20V DC because the voltages on the t-con are either typically 5V or 12V DC. However, since you are gett 0.5 on each side, it sounds like there is no power being sent. If the t-con fuse is good, then that suggests something might be wrong on the logic board.

3) There are 4 voltage regulators that I can see. I circled them in red.

4) Put your multimeter on 20V DC. Put your black probe on a ground screw on the logic board. Leave it there for all readings. This is your ground.

5) Put your red probe on each pin including the "cut" pins, but ignore the "fat tab". The "fat tab" is north. Number the pins left to right.

6) List all your readings like so for each regulator.

Q1
part number 1084-33
pin 1 = 0.0V
pin 2 = 3.3V
pin 3 = 5.0V

[retiredcaps]

Re: DELL 2405fpw

I just lifted the metal shield enough to test the fuse with the DMM and it was fine.

Did you use continuty to test the fuse or ohms? A good fuse should read less than 1.0 ohms.

[Mirage00]

Re: DELL 2405fpw

To test the fuse I used ohms. Set the DMM to 200 and it read .2

[Mirage00]

Re: DELL 2405fpw

Also, when I set the DMM to 20DC V to test both sides of the fuse, I don't get any reading it stays at 0.00 This is why I kept lowering the DCV to the lowest setting of 200m. I switched the ground hole I used to the double screw hole on the left of the board and it read 1.0 on each side of the fuse. If I left the probes on it would slowly drop .1 or .2

[retiredcaps]

Re: DELL 2405fpw

To test the fuse I used ohms. Set the DMM to 200 and it read .2

That definitely is a good fuse.

[retiredcaps]

Re: DELL 2405fpw

Also, when I set the DMM to 20DC V to test both sides of the fuse, I don't get any reading it stays at 0.00

That means no power is going to the t-con board, but we know for sure your fuse is good.

List your voltage regulator readings with part numbers and we can see if one of them are bad.

[budm]

Re: DELL 2405fpw

That means the main board is not sending out the 5v or the 12v to the T-CON, this is done by switched transistor (this transistor is turn on when the monitor detects the video signal) some where on the main board.

[Mirage00]

Re: DELL 2405fpw

Ok. I had to leave the DMM on 200m for the voltage readings.

part number F5305S
pin 1 = 1.5V
pin 2 = 0.0V
pin 3 = 1.5V

part number FR9024N
pin 1 = 1.5V
pin 2 = 0.0V
pin 3 = 1.5V

part number H183
pin 1 = 0.0V
pin 2 = 0.0V
pin 3 = 0.0V

part number H185
pin 1 = 0.0V
pin 2 = 0.0V
pin 3 = 0.0V

[retiredcaps]

Re: DELL 2405fpw

Ok. I had to leave the DMM on 200m for the voltage readings.

part number F5305S
pin 1 = 1.5V
pin 2 = 0.0V
pin 3 = 1.5V

part number FR9024N
pin 1 = 1.5V
pin 2 = 0.0V
pin 3 = 1.5V

Please redo the two above with your multimeter on 20V (twenty). Do you have power on and lcd plugged in?

[Mirage00]

Re: DELL 2405fpw

That means the main board is not sending out the 5v or the 12v to the T-CON, this is done by switched transistor (this transistor is turn on when the monitor detects the video signal) some where on the main board.

Some sort of signal is being detected because when the backlight turns of after 30-40 seconds, if I toggle the monitor output on my laptop that is connected to the 2405fpw the backlight turns back on again. So it senses some sort of signal from the laptop. Also, I mentioned in the first post the OSM does not display.

[Mirage00]

Re: DELL 2405fpw

Please redo the two above with your multimeter on 20V (twenty). Do you have power on and lcd plugged in?

No the lcd is unplugged. Does it need to be on? If so, can I plug it in and turn it on without the tcon board connected (I took it out for pictures and testing)

[retiredcaps]

Re: DELL 2405fpw

If the IC has more than one line on its part number, please list them all. For example H183 has 950T65.

[budm]

Re: DELL 2405fpw

I know that the monitor detects the signal from the PC OK, but the main board is not turning on this transistor to supply the voltage to the T-CON board, that what we will have to trace out the B+ line from the T-CON connector to see where it goes to. There may be another fuse on the main board also, I cannot find any service manual for this monitor yet.
It will have to be troubleshoot down to the component level at this point.

Well, after reading post 16, I may have to disregard my troubleshooting method until we get more info.
"No the lcd is unplugged"

[retiredcaps]

Re: DELL 2405fpw

No the lcd is unplugged. Does it need to be on? If so, can I plug it in and turn it on without the tcon board connected (I took it out for pictures and testing)

Yes, power has to be on for all voltage measurements. Let's start again with the voltage measurements on t-con and then the 4 voltage regulators (with all the part numbers on the IC).

Put your multimeter on 20V DC.

[budm]

Re: DELL 2405fpw

And hook it to running PC also, otherwise it will go into standby mode.