BENQ G2420HD - no HDMI signal

[are3z]

Hi everyone,

few days ago my LCD monitor stopped working correctly with my laptop - I used to work with this setup since 8 years.

The BENQ LCD goes on, shows the purple screen with BENQ logo and then the blue screen with the no HDMI signal message. After few secs it goes off (like there is no cable connected).

I checked:
- other HDMI cable
- another laptop
- VGA, DVI (same effect)
- the monitor reacts to cable connection, few secs of black screen-green diode, then again the blue screen
- the backlight works correctly, with disconnected LVDS it shows white screen with light

I found the service manual (Product Service Manual II for G2420HD) and checked:
- transformers work correctly (checked voltage and resistance using meter)
- one bulged capacitor (replaced)
- Zener diodes work one way. One diode seemed to work both ways, I desoldered it and checked, it was ok then
- IC TL1451ACN gives 5.6V, there is no 3.3V output, but I understand it's due to lack of components on PCB (seems that this model doesn't need 3.3V, hope that's correct?)

I'm looking forward to any hints on how can I proceed with checking. It doesn't seem that the Realtek chip is wrong or has cold solder joints.

Thank you in advance!

EDIT:

- VGA works! It just started working. It looks that the problem is with HDMI?

[R_J]

Re: BENQ G2420HD - no HDMI signal

Check the hdmi jack pin connections to the pc board, there could be a poor soler connection, try moving the jack pins on the board to see if any are loose.

[are3z]

Re: BENQ G2420HD - no HDMI signal

Hi R_J, thank you for responding!

Once I noticed that the VGA works, I checked pins, but didn't notice any loose one between HDMI<->PCB, PCB<->RTD. It seems that they're soldered well.

Considering the fact that I'm able to use VGA output, does it mean that all ICs seem to work? I was wondering if there might be any dead one.