Dell 2007FPb problem

[schnee]

Hi,

this is my 1st real post on this forum. :-)

My son has a Dell 2007FPb monitor, whic a few weeks ago started to act oddly: it was woring for a 30-40 minutesm, then turned off. It was possible to turn it on with unpluging and replugging the mains cable. A few days later is stopped working.

I had no time till now to look into the device. Thanks to threads on this forum i was able to repair the power supply on the USB board (i had to replace a small resistor which was out of spec - 47 kOhm). So now the monitor has power, recognized by the computer, but screen stays empty - no osd, no data displayed from the computer.

I checked, based on the threads the following voltages:
Main power:
- 19 VDC - OK

USB board:
- 3.3 VDC - OK
- 5.0 VDC - OK
- 12 VDC - Not OK, but it is only for the sound barm which i do not have

Logic board:
- 3.3 VDC - OK
- 2.4 VDC - OK
- 1.8 VDC - OK

LCD control board:
- 19 VDC - OK
- 3.3 VDC - OK
- 1.8 VDC - OK

I am bit lost now, where to look for the problem: the logic board seems to be OK, as power levels are OK and also the computer recognizes the monitor (and the monitor comes out from standby when attached to the computer). The LCD board was working fine before the problem occered and currently i was unable to identify any blown fuse or missing power in the card.
I hope that somebody on this forum can give me some hint, direction to follow next.

Thanks

ps: I posted some picutres of the above boards too.

[cpt.charlie]

Re: Dell 2007FPb problem

Do you see any background image at the panel? Does the backlight turn on? Make sure you have connected properly the LVDS cable, move gently the cable while the monitor is working and look for changes.

[schnee]

Re: Dell 2007FPb problem

I rechecked everything today. I do not see any background image on the panel. The backlight turns on. Monitor reacts on the front panel buttons, computer regnize it when plugged in etc.

I tried to move the LVDC connectors on both ends, but nothing changed. I checked the cable with an ohm meter and all wires a good and did not find any shorts between pins.

Do you have any other suggestions?

[schnee]

Re: Dell 2007FPb problem

Found some documentation on the screen (LM201U05)https://dev.xdevs.com/attachments/do...2_final_1_.pdf and made some measurements on the control panel for the LCD. All measured voltages are in spec.

[cpt.charlie]

Re: Dell 2007FPb problem

You could check the sinal pairs, but you will need an oscilloscope.

[schnee]

Re: Dell 2007FPb problem

Don't have access to oscilloscope unfortunately....

Does any of these boards have a serial/debug output to connect them to a computer and see the output?

[stj]

Re: Dell 2007FPb problem

i do see a space for a 4pin connector - pin4 is gnd.
no idea what it's for though.

[cpt.charlie]

Re: Dell 2007FPb problem

maybe a bad solder joint?

[schnee]

Re: Dell 2007FPb problem

i do see a space for a 4pin connector - pin4 is gnd.
no idea what it's for though.

Those pins are connecting to the main IC and definitelly looks like a serial port. Will try to find spec for the FLI-5961-LF before connectiing anything to the pins. Would really appreciate if someone could post the chip's datasheet, as a quick search did not show up results.

[stj]

Re: Dell 2007FPb problem

page136

[schnee]

Re: Dell 2007FPb problem

page136

Thanks!