Odd Software for Odd Jobs

Fixing my Dell 2408 monitor

For many years I've had an Apple 24" screen twinned with a Dell 24" screen (both 1920x1200). However when I returned from my trip to Townsville, my Dell screen appeared to be dead … the green power LED was lit but the screen was blank.

Puzzled, I did some searching on the web - the opinion seemed to be either a blown fuse (but the power LED was lit) or an issue with the backlighting. Ahhh, no backlighting means a pitch-black display.

Dismantling the thing was the first hurdle - no screws to be unscrewed. More research showed that you need to prise the bezel off the front of the screen first.

Once inside I was presented with my first look of a flatscreen monitor's innards:

2016-12-03 15.26.36

The power comes into a small board, which is fed to another board with a few capacitors and transformers (where the main voltage conversion occurs?). This is connected to the main logic board (I guess) with all the various input sockets and a pair of heatsinked processors.

An additional daughterboard on the right plugs into the logic board to provide the additional USB hub and card reader functionality (note-to-self … if the screen dies completely, rescue this board):

Dell 2408 USB daughterboard

The power board also connects to the backlight daughterboard:

Dell 2408 backlight daughterboard

So, why wasn't the backlight working? With power connected, I measured the voltage being fed into the backlight board from the power board - I read that it should be 24V DC. Measuring between GND and each VIN showed 0V.

2016-12-04 10.45.50

So that's pretty obviously the problem - no power to the backlights, no backlighting, no display.

I checked all the capacitors - they looked fine. I then reseated all the cables.

I then noticed the backlights came on, through the holes in the board where the screws had been:

2016-12-04 10.53.22

Checking the display, I could now see images (menu, etc.) being displayed on the screen.

Cool. So it was "fixed". I decided to leave the screen out in the workshop, replacing the older 19" screen I had, as it was more versatile (more input options, USB hub). And I'd gotten used to using the Mac Pro with just a single 24" display anyway!