bad color on VGA

[klotzmando]

I am using a ACER P2442 monitor with the android image on OlinuXino-A13 WIFI powered with 12 VDC on the barrel connector.
The video look very bad. The colors are off and the text seems to have sometimes red and sometimes blue halos.
If I could figure out how I would attach a picture of what I am seeing.
Does anyone have any suggestions?
https://picasaweb.google.com/lh/photo/pROvnWMbhNSNOK07aJ_1erD9Lo_hM0cTEmKUMykSpJk?feat=directlink

[klotzmando]

A follow-up. I hooked a logic analyzer to the LCD output RED pins and it looks like all the signals are changing correctly, so it may be in the D/A conversion R ladder network or buffers. The pins are to fine for my probes to attach to them, I may have to take it to work for a better look.

[LubOlimex]

Hey klotzmando,

Is it possible for you to take a good HQ picture of the board's top side? Is it possible also to check the signals after the buffers - whether they are the same as before the buffers (this indeed might a problem with the resistor matrixes after the buffers)?

Best regards,
Lub/OLIMEX

[klotzmando]

I brought the board to the lab where I work. Here we have some more sophisticated tools so it was easier to troubleshoot.

• A logic analyzer apparently was not the best tool to use. When we tried to trouble shoot at the buffers we noticed that the signals on LCD_022 and LCD_023 were not as clean as they looked on that analyzer.
• Back at the LCD connector we noticed that only the LCD_022 and LCD_023 pins exhibited the strange wave form. Instead of switching between 0 and 3.3 volts as expected, they sometimes switched to approximately half way in beteen.
• With the power turned off, we measured the resistance between each of the LCD pins. All of the pins other than Pin 11 (LCD_022) and Pin 12 (LCD_023) measured around 6 meg Ohms. Pin 11 to 12 was 45 Ohms. Approximately twice the resistance of the RM18!
• Close examination with a powerful micro scope fround that there was a solder bridge between pins 1 and 2.
• Once the solder bridge was removed, the colors on the display looked much better.