Dell u2312

[retiredcaps]

Re: Dell u2312

EN = 0v
ENA = 0.0v
EN = 0.102v

I don't know which of the above is the command to turn on the PSU. So my next suggestion would be to trace all of the above pins to see if a transistor is shorted.

Are there any components on the backside of the main board?

[Jasgriff]

Re: Dell u2312

Had to order some clips to hold my probes on whilst I was pressing the buttons so sorry for the delay.

I have 3.3v on the on/off button and when its pressed it goes down too 0v.

[retiredcaps]

Re: Dell u2312

See if the voltages go to the front keyboard. See if pressing the on/off button causes a voltage change or not.

[Jasgriff]

Re: Dell u2312

The power LED doesnt come on at all.

[retiredcaps]

Re: Dell u2312

Does the power led come and stay on?

[Jasgriff]

Re: Dell u2312

Right done a little measurements from P802 on the power supply which connects to the signal board.

PWM = 2.514v
EN = 0v
5v = 5.209v
5v = 5.209v
5v = 5.209v
GND = 5.209v
GND = 0v
5v = 0v
ENA = 0.0v
EN = 0.102v
5v = 5.209v
RTNA = 0.008v
DET = 0v

After looking at the markings and then trying to double check them as it didnt seem right I noticed that they have put the connector on back to front.

Has anyone ever seen this before?

[Jasgriff]

Re: Dell u2312

Ok,

There were a number of fuses that seemed to be connected to the on board usb ports and the external ones. I checked them both and none were blown. I then reconnected the external usb's and tested for voltage again and still got nothing I also tried a usb stick with a light on in the on board and and external usb and that didn't have any sign off life either.

I am now thinking that there should be 5v's kicking about going into the usb's that maybe also fed the third voltage regulator?

[retiredcaps]

Re: Dell u2312

I302
LD1117AG
12A010HUE

Pin 1 = 0v
Pin 2 = 1.205v
Pin 3 = 3.345v

Okay, I302 is good. Move onto jetadm123's suggestion.

PS. Is the power LED on at all?

[jetadm123]

Re: Dell u2312

You jarred my memory with the USB card. It's true that some other Dell models required the usb card be connected in order for to start. I don't know if it applies to your model. Before you connect the usb card, inspect it for a blown fuse. If the fuse is good, then connect it and check I308 again.

[Jasgriff]

Re: Dell u2312

Right,

I301
N252
G1084-33

Pin 1 = 0v
Pin 2 = 3.345v
Pin 3 = 5.209v

I302
GTC
LD1117AG
12A010HUE

Pin 1 = 0v
Pin 2 = 1.205v
Pin 3 = 3.345v

I308
Dll1ib
17-33

Pin 1 = 0v
Pin 2 = 0v
Pin 3 = 0v

On the Fuses. I meant 0.2 Ohms again my mistake.

Looking at I308 it seems to be connected to the USB hub which this monitor has. I do recall someone on here mentioning that the monitor wont power up without the usb hub connected?

[Jasgriff]

Re: Dell u2312

No properly working Fluke will give a reading of 2.0 ohms for a fuse. You must mean 0.2 ohms.

Details and precision matters (as per post #9). I would like to see all the digits (resolution) of the readings.

You get great marks for clear focused photographs.

Retiredcaps all valid points and again noted.

I did a little playing around with the monitor again this morning so I will write up my findings shortly along with some accurate readings.

[retiredcaps]

Re: Dell u2312

Yes there is a F301, F304 and F305 too they are all measuring 2 Ohms

No properly working Fluke will give a reading of 2.0 ohms for a fuse. You must mean 0.2 ohms.

Details and precision matters (as per post #9). I would like to see all the digits (resolution) of the readings.

You get great marks for clear focused photographs.

[retiredcaps]

Re: Dell u2312

Right...

I301 = 3.3v
I302 = 2.1v
I308 = 0v

P306 is a ribbon connector that connects to the switch panel. There seems to be 3.3v present on some of those pins.

I prefer readings for all the 3 pins for a reason.

The reason is that I302 could an adjustable regulator or it could be a fixed regulator. The 2nd line of the part number begins with 12 would could mean it is a fixed 1.2V regulator. If I'm correct, pin 1 on I302 should be 0.0V volts. That would mean I302 is bad (unless you transposed the numbers).

I'm leaning towards a fixed regulator because I see no SMD resistors between pin 1 and pin 2.

This is why I wrote the guide to ask for all readings. There is a lot of mis-interpretation of the readings by people.

[jetadm123]

Re: Dell u2312

I308- The rightmost leg is the input. Left leg is ground and middle leg (and tab) is the output. Try tracing the input leg to see what's feeding it.

[Jasgriff]

Re: Dell u2312

Yes there is a F301, F304 and F305 too they are all measuring 2 Ohms

[jetadm123]

Re: Dell u2312

Are you talking about F302 and F303?

[Jasgriff]

Re: Dell u2312

Im getting nothing at all on any pin of I308. There are a few SMD fuses on the board too which I have been testing none of which are blown so far.

[jetadm123]

Re: Dell u2312

I308 is a 3.3V output regulator. Are you at least seeing a 5V input for I308?

[Jasgriff]

Re: Dell u2312

Right...

I301 = 3.3v
I302 = 2.1v
I308 = 0v

P306 is a ribbon connector that connects to the switch panel. There seems to be 3.3v present on some of those pins.

[retiredcaps]

Re: Dell u2312

The monitor when plugged in shows no sign of life at all.

If the power LED is green, that implies the main board is working.

If there is no power led at all, then check the voltage regulators using my guide below.