No Power Dell U2410 Monitor

[Kiriakos GR]

Re: No Power Dell U2410 Monitor

Mate if you do have access in all that equipment and still you are looking answers over the internet, something smells bad.
Either way good luck.

[dinamichhhh]

Re: No Power Dell U2410 Monitor

see picture:
What do you get at B1, 2, and 3?

I got excacly the same results as previosu posters.

When power and main board are connected together we get:
* B1 3.7V
* B2 0V
* B3 0V

When they are disconnected we get:
* B1 5V
* B2 0V
* B3 0V

Voltage at B2 is blocked by N channel mosfet, drain side has 12V. Voltage at B3 is blocked by some other part, probably some kind of voltage regulator, its source voltage is also 12V and present. They are probably turned on later by CPU when monitor starts working.

My first thought was, that 3.7V at B1 is not right. But after inspecting power board I found out that signal from pin 1 (red wire) is used by CPU to drive a gate of smal fet transitor which when opened/closed causes resistance change in a part of circuit that drives led in one of two feedback opto-couplers. So it looks like 3.7V is indeed intended voltage at power off state and is later ramped up via CPU and pin 1 to 5 volts.

What is also strange is that USB ports are supplied from this 3.7V (or 5V) power line via some kind of switch (probably mosfet). And in my case the switch is turned on, thus providing 3.7V at USB ports. Which is strange and should be 0V in power off state. This is another example of CPU driving some signal to wrong value.

Based on all that I say that:
* power board is ok
* CPU is stuck and does not wake-up when power button is pressed. Why? Tin whiskers maybe?

Tomorrow I will carefully try to re-flow CPU and SRAM chips with handheld hot air soldering station. They are both BGA so my hopes are low.

Thanks for help. Any more suggestions?

[dinamichhhh]

Re: No Power Dell U2410 Monitor

Mate if you do have access in all that equipment and still you are looking answers over the internet, something smells bad.
Either way good luck.

Thanks for support. I am indeed an electrical engineer, but I am mostly working on software side of embedded projects.

When you get a board like this without any schematics it is difficult to do anything. I tried the obvious stuff, then read all the information I could find via google and then tired some more test. When I got stuck without further ideas to try I posted to this forum.

[dinamichhhh]

Re: No Power Dell U2410 Monitor

I haven't given up, yet

I uploaded a bunch of photos showing dis-assembly, boards and part of schematic. You can find them here.

[dinamichhhh]

Re: No Power Dell U2410 Monitor

Time to recap and look back.

My problem with U2410 is that it wont power up. When connected to mains it just stays off, no light, no leds, nothing. Pressing power button does nothing. Leaving it unconnected for a long time did not solve anything.

Since my warranty expired one month ago, I took it apart and looked inside with multimeter oscilloscope and ESR meter.

No obvious fault was found after visual inspection (also with microscope), no bulging or leaking caps.

Measured all electrolytic caps (in circuit) with ESR meter, again no problems found.

Measured all diodes, fuses, inductors, all good.

Checked power button, no problems there.

Measured various voltages on power and main boards when connected to mains voltage.

Traced boards and drawn schematics.

In my next posts I will publish schematics and my measurements.

[dinamichhhh]

Re: No Power Dell U2410 Monitor

Power board:



Here is a part of power board circuit, the output stage that generates three voltages for main board. This part is connected to main board via 14 pin connector/cable, pin 1 is red color others are black.

Measured voltages are drawn on schematic in red color. These are measurements of my device when all boards are connected together, plugged into mains 235V 50Hz AC.

The most important part is voltage at point V2, which is supplying main board via pins 11-14. This voltage level is controlled by CPU on main board via pin 1.

When pin 1 is pulled down (zero volts), the expected voltage V2 is defined by voltage divider with 10.5k and 22k resistors and should be 3.7V. This is exactly the same as I measured.

When pin 1 is pulled up or left open, the expected voltage at V2 is now defined by chanded divider- a 18k ohm resistor is paralleled to 22k, giving voltage of 5 volts.

So this power supply is designed in such a way that it supplies either 3.7V or 5V to main board! Since pin1 is 0V in my case, output voltage V2 is 3.7V.

There is also almost no ripple voltage on V2 - caps are ok. There is some ripple (arround 300mVpp) at V1, looks like 10kHz switching frequency.

Pin 2 is also off - so back-light regulator is off at this time.

Voltages at pins 8,9 (for external speaker bar) and pin 10 (LCD panel) are 0 at this time, they are controlled by CPU via pins 3 an 4 (haven't traced this part of board in detail).

So all in all it looks like my power board is functioning as designed, based on inputs it receives from main board.

[dinamichhhh]

Re: No Power Dell U2410 Monitor

Main board:



Here is a rough schematic of power distribution on main board. Measured voltages are in red.

As we can see, the board is supplied with 3.7V at pins 11-14, since CPU is driving pin 1 to 0V.

At the same time CPU is also driving Q702 on, which supplies USB hub and USB ports with 3.7V. At the same time linear regulator AS1117L which should generate 3.3V for USB controller can't deliver 3.3 volts and only manages to output 2.7V. This means to me, that when Q702 is switched on, the voltage on pins 11-14 should be 5V! When supply voltage is switched to 3.7V the Q702 should be off, turning off USB part of circuit!

Looking at other regulators, they all seem to be ok. Forgot to draw a voltage on output of first switching regulator - it is 3.4V.

So CPU is getting all supply voltages, so is SRAM. The clock on CPU is running (measured with scope). But the output from CPU is not valid. Here are possible scenarios:

* If monitor is in power off mode, then pin 1 pulled down is ok, but opened Q702 (USB power) is not - it should be closed.

* If monitor is powered on, then pin 1 should float - but is pulled down. The Q702 is on, which is ok in power on mode.

I think my CPU is confused or not starting up or stuck or something. It is probably end of my repairs since I could not find any obvious JTAG or serial interface to CPU to check if it is alive.

Time to look for another monitor..., rest assured that it wont be DELL since they do not support their products beyond warranty. Official from dell wrote on their forum, that they do not service broken monitors or stock replacement parts. If monitor is in warranty, they replace it, if it is not, you can throw it into garbage - you can't get a replacement parts or service manual.

At least I hope that my photos, schematics and measurements help somebody else in future.

Damjan

[AndrewNN]

Re: No Power Dell U2410 Monitor

Monitor not ON. C854 - 320V. PCF did not work. When the monitor is off voltage should be ~ 400V on C854? Broken SG6901ASZ ?

[AndrewNN]

Re: No Power Dell U2410 Monitor

Hello!

I had the same trouble with the monitor. Need to resolder D930, D960, Q950.

I got excacly the same results as previosu posters.

When power and main board are connected together we get:
* B1 3.7V
* B2 0V
* B3 0V

When they are disconnected we get:
* B1 5V
* B2 0V
* B3 0V

...
Thanks for help. Any more suggestions?

[ficobel]

Re: No Power Dell U2410 Monitor

Hi,
I have 2410u Dell . so, i smell burned part's inside, so, the scrreen still working...i found the fr851 burned on the power supply board.this component it completly distroyed... someonecan help me to know how to replace it? (value of the component) and why it's burned ?? did i found others burned too ?

thank's

[ficobel]

Re: No Power Dell U2410 Monitor

hello,

what is th reference and value of FR851 ?

thanks .

[ficobel]

Re: No Power Dell U2410 Monitor

hello,

what is th reference and value of FR851 ?

thanks .

[jusatone]

Re: No Power Dell U2410 Monitor

Hello everyone,

I also have a problem on my U2410,
the backlight turns on for 3 seconds and then goes off, I feel it does not detect the input video hdmi or dvi or vga.

I replaced every capacitor in the power supply board and redid the D930 welds, D960, Q950.

I tested this component is there are good


Hello everyone,

I also have a problem on my U2410,
the backlight turns on for 3 seconds and then goes off, I feel it does not detect the input video hdmi or dvi or vga.

I replaced every capacitor in the power supply board and redid the D930 welds, D960, Q950.

I tested this component is there are good

but still nothing.

I managed to update the firmware to the latest version by usb

but still nothing.

I do not understand or can come the problem.

Do you have an idea thank you?

[jusatone]

Re: No Power Dell U2410 Monitor

Hello everyone,

I also have a problem on my U2410,
the backlight turns on for 3 seconds and then goes off, I feel it does not detect the input video hdmi or dvi or vga.

I replaced every capacitor in the power supply board and redid the D930 welds, D960, Q950.

I tested this component is there are good

but still nothing.

I managed to update the firmware to the latest version by usb

I do not understand or can come the problem.

Do you have an idea thank you?

[Anatoly71]

Re: No Power Dell U2410 Monitor

Hello,

I bumped into the same problem. I checked the voltages, etc. and see 100% the same as dinamichhhh carefully described. In short the PS is OK, the motherboard is failed. Most likely it is FW problem so there's no way to fix it.

I've bought the motherboard through ebay (used but working), changed it and the monitor works again!

Thank you all so much and very special thanks to dinamichhhh!

[nike32]

Re: No Power Dell U2410 Monitor

Hi all!
I have the same problem with backlight. Two times in one year. First time U2410 was repaired during garanty period (motherboard replacing), but now it's dead again. Plan to kick off all the lamps and install led backlight.

[vidua]

Re: Dell U2410f: Q853 and FR851

Hi all,

could some kind person please tell me and ficobel what values

FR851 and Q853 have?

Hampus has measured ~1Ohm for FR851 but i haven't found any info about Q853.

I have a Dell U2410f with broken Q853 and FR851, no way to read anything on them as they are exploded/burned completely.

There is a good chance that there is no other problem with my monitor and i could help you with measurement values from a working set after repair!

So please help, thanks!

[vidua]

Re: Dell U2410f: Q853 and FR851

Hi all,

half an hour later it seems i have found what i am looking for :-) :

Q853 = F15NM60N (ST = SGS-Thomson) N-channel 600V - 0.27Ω - 14A - FDmesh™ II Power MOSFET D2PAK, I2PAK, TO-220, TO-220FP, TO-247

check here:

https://www.badcaps.net/forum/showth...t=17767&page=3

there is no direct reference but post #16 suggests

FR851 = 0.2 Ohms fusible resistor (2-3 Watts i think...)

BIG THANKS to WASMUNDT !!

[selldoor]

Re: No Power Dell U2410 Monitor

For the fusible resistor if you look at this series of pictures
http://www.auctiva.com/hostedimages/...0,0,0&format=0
you can see fr851 and its marking. In another picture there is another resistor on the board he same, so if you can find that on your board - Bingo

[Gulz]

Re: No Power Dell U2410 Monitor

hi guys i have an issue with my u2410f power board, there's a resistor that's clearly blown and i cant for the life of me find the value for it. is there any schematics for the psu, or even a picture of the board so i can try see and match up the resistor i need https://www.badcaps.net/forum/images...s/confused.gif