No Power Dell U2410 Monitor

[ForensicFixer]

Re: No Power Dell U2410 Monitor

Sorry for going quiet over Christmas, a busy time here.

But now back to the grind :-;

@selldoor I traced pin2 and found it at this pin marked in red in pictures. What is this component?

I retested the power board with a 24volt 24w bulb on the 5v rail and the supply voltage held steady at 5.14volts.

Attaching the mainboard pulls the voltage down to 3.7v but the recovery to 5.14 is immediate when disconected.

[selldoor]

Re: No Power Dell U2410 Monitor

@jetadm123 a track runs from pin 2 on the under side then through the board just above u930. after feeding pin 4 it runs to R934 just below cap931 (bottom left of earlier picture).

Can either of you trace where pin 2 goes to on the main board

[davor]

Re: No Power Dell U2410 Monitor

Just a note: I can extend display from laptop to Dell with no problem, arrow disapears on Dell...hm, maybe I can use flashlight instead LCD backlight?
What if problem is hidden on 3rd board, high voltage for BL control?
Not happy with that!

[ForensicFixer]

Re: No Power Dell U2410 Monitor

Ok applied 5v to pins 1-4 on mainboard, it actually reads 5.06v and remained constant. It drew 2.1 mA and again remained constant. Pressing the power button caused no changes.

In selldoor's image left most regulator is u701 and marked as AS1117L-33.
Pin1 = 0, Pin2 = 3.31, Pin3 = 5.06 Datasheet shows 3.3 out on pin2 which is correct.

Next is u505 marked as AP6260 12 GJFS
Pin1 = 0, Pin2 = 1.2, Pin3 = 3.40 Datasheet shows 1.2 out on pin2 which is correct.

Far right is u503 marked as AME8815 AECS180
Pin1 = 3.40, Pin2 = 0, Pin3 = 1.81 Datasheet shows 1.80 out on pin3 which is correct.

I think this puts us back to the power supply??

[ForensicFixer]

Re: No Power Dell U2410 Monitor

Sorry Guys

Got side tracked with my paying work!

Checked the three fuses all show good. Had previously checked the two regulators on the left. They returned the expected voltage drop but the input voltage was reflecting the pulled down voltage on the 5v line. I have the exact values but their at home and I'm not.

I also checked the three zener diodes and transistor situated with the opticouplers. These all returned expected behaviour.

My next plan was to supply a known good 5v feed to the main board to at least rule the mainboard out of the equation.

Any thoughts regarding the best way forward?

[selldoor]

Re: No Power Dell U2410 Monitor

Davor -Ha ha - perhaps he is waiting for the picture I forgot to upload

Here it is - in conjunction with post 31

[davor]

Re: No Power Dell U2410 Monitor

Any prrogress anywhere?
After all checks I'm still in the dark.
Placed a call onto Dell service where guy said: yeah, we can easely repair all!
So maked a 60km trip and than another "Dell" changed picture: yeah, diagnosis is 40eur...
Replayed: OK, than when you find component(s) it must be few euros more and more or less is cost.
Dell: WTF component means!? I don't even know about soldering - we just replace boards!
Me: engine start, 60km back..........

[selldoor]

Re: No Power Dell U2410 Monitor

I have tested Q930 and U930 can you point out other voltage regulators?

Have attached the mainboard photos below.

Cant read the part numbers so not really I have marked some of what I think are Vrs but could be mosfets you will need to tap the part numbers into your browser and see what they are.
I have also marked the two G fuses - might as well check those and on the right there is a yellow rectangular fuse which I think is a resettable - better make sure it has reset( Just test as a normal fuse)

[ForensicFixer]

Re: No Power Dell U2410 Monitor

@jetadm123 a track runs from pin 2 on the under side then through the board just above u930. after feeding pin 4 it runs to R934 just below cap931 (bottom left of earlier picture).

[budm]

Re: No Power Dell U2410 Monitor

You are corect that the first 4 PINS are the control lines, they are more likely to be:
>3VDC = ON, 0V (<1V) = OFF
PS_ON which will turn on the PFC Vottage booster cricuit.
BL_ON for backlignts on.
Dim for backlights dimming
Last one probably turn on that regulator IC and the MOSFET.

All those traces need to be traced out.

[jetadm123]

Re: No Power Dell U2410 Monitor

What's supplying pin 4 of the U930 regulator?

[ForensicFixer]

Re: No Power Dell U2410 Monitor

Thanks selldoor

The torpedo fuses both read 0.1 on 300ohm range, the fusable resistor flashes a different figure each time then goes to infinity.

Voltages are all zero against ground screw and board powered. Expected this as this side (backlight inverter) only fires up after command from mainboard. At the moment can't get the 5v standby voltage into mainboard.

I have tested Q930 and U930 can you point out other voltage regulators?

Have attached the mainboard photos below.

[selldoor]

Re: No Power Dell U2410 Monitor

I will let Budm comment - ( i dont follow circuits too well)
On a more basic subject, can you check the two fuses (red torpedos) and the Pink
fusible resistor ( Power off meter on ohms 200) bottom right corner in pic

After you have checked for continuity can you check the voltage on each side of each
against an earth screw

As the problem may be main board related can you do good clear pics of the main board
front and back.

I see there are some voltage regulators on the main board if you can locate and check them
as in here
https://www.badcaps.net/forum/showthread.php?p=261329

[ForensicFixer]

Re: No Power Dell U2410 Monitor

Hi Guys
I know this will sound a bit basic but I'm still in the early learning phase. I would be grateful if you could bare with me and add any corrections or thoughts.

I spent a bit of time looking at the low voltage circuits on this board and what is presented at the connector. Looking at the board underside with red wire being pin 1 on left I came to these conclusions.

Two schotty diodes take take 12.98v and 5.13v off the transformer.
Pins 5,6,7 are ground.
All higher numbered pins supply power to the motherboard and thus have heavier tracks.
Pins 8,9 supply power switched by the mosfet Q930.
Pin 10 supplies power switched by the AX1202 U930.
Pins 11-14 supply 5.15 directly from one of the schotty diodes.
Pin 3, 4 probably control lines, run to the back light inverter.
Pin 2 control wire to switch on moshet Q930 and regulator U930.
Pin 1 runs to optoisolator area

Pins 11-15 are showing 5.15v without load which is probably correct but gets pulled down by the presence of the second board.

Pin 1 is showing 4.68v (odd value when nothing connected) and it is more than likely a control line running to the optoisolator area which I believe is used to regulate power output.

So the question is, should it be providing a voltage? and are there any tests I can perform to check this area out.

All thoughts and corrections much appreciated.

[Kiriakos GR]

Re: No Power Dell U2410 Monitor

Thank you @ForensicFixer and @selldoor, yes this large "G" caught my eye too.

But my warranty is active until January 2014 and I am unable to open it up.
At list now I am some how prepared of what to expect, thanks again.

[budm]

Re: No Power Dell U2410 Monitor

I have a feelings that the MOSFET and the regulator are turn on by the main board when you hit the power switch, need to find that control line, it must be on one of those pins. That may explain why B+2 and B+3 are 0V.

[jetadm123]

Re: No Power Dell U2410 Monitor

Measured the voltage on the regulator with mainboard disconnected. Pin 5 'vcc' 12.99v and 0v on 'out' pin 3.

You also have to measure pin 4, which is the Voltage Enable. You must have a voltage applied to pin 4 to turn the regulator on, which in turn produces Voltage Output on pin 3.

[ForensicFixer]

Re: No Power Dell U2410 Monitor

Measured the voltage on the regulator with mainboard disconnected. Pin 5 'vcc' 12.99v and 0v on 'out' pin 3.

[ForensicFixer]

Re: No Power Dell U2410 Monitor

Yeh realised my mistake and couldn't leave it!!
I'm guessing the test is between ground, vcc and out. That would make it pins 1,3 and 5.
Am I looking for similar results?

[selldoor]

Re: No Power Dell U2410 Monitor

I did a quick test on the mosfet in circuit using the 200 ohm test.
Pin 1 - 2 open circuit
Pin 1 - 3 open circuit
Pin 2 - 3 sometimes flashes 165.9 then open circuit, other times open circuit

I won't be home again till Tues night so will test the mosfet then.
What do you think of the regulator results?

Hmm The 3 pin one is the mosfet it looks ok

The 5pin one is the regulator - you need to look at the datasheets