Poor contrast ratio on my CFAG320240CX-TFH-TTS

[jon_co]

Hi,
Ive just finished some test on my current test screen (brand new CFAG320240CX-TTI-T) and everything is working perfectly. Ive then swap the display for the CFAG320240CX-TFH-TTS, also brand new, and noticed the contrast a bit fade comparing to the actual shot on the website:

Crystalfontz pic:

I managed to adjust the contrast pot to an optimum but still, i really dont understand why it isnt as clear and crisp as my CFAG320240CX-TTI-T and the shot from Crystalfontz...

My pic: (not the best quality but it show the actual contrast pretty well)

ive tested the voltage on the pin 3 and its exactly at -23.7v. What should i look for to correct this issue? Is this LCD defective?

thank you!

Jo

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[jon_co]

heres a picture of the CFAG320240CX-TTI-T displaying the same data:

Its way better with this one, but unfortunetly, i really need the CFAG320240CX-TFH-TTS.

 

[CF Tech]

When you adjusted for the Vo, did you make the adjustment while watching the screen to find the optimal setting? The -23.7v is a good starting point, but the optimal voltage may vary a bit from unit to unit.

The touch screen will reflect a bit of ambient light, making the dark areas look a bit lighter, if the display is in a bright environment. When we take our photos, we have a setup that minimizes the ambient reflections, so that might account for some of the differences in the two photos.

Another possibility is that there might be some control register that does not have the optimal value written to it, but I would not think this is the problem, since the other display looks OK.

 

[jon_co]

When you adjusted for the Vo, did you make the adjustment while watching the screen to find the optimal setting? The -23.7v is a good starting point, but the optimal voltage may vary a bit from unit to unit.

The touch screen will reflect a bit of ambient light, making the dark areas look a bit lighter, if the display is in a bright environment. When we take our photos, we have a setup that minimizes the ambient reflections, so that might account for some of the differences in the two photos.

Another possibility is that there might be some control register that does not have the optimal value written to it, but I would not think this is the problem, since the other display looks OK.

Yes, the display was adjusted while it was displaying the actual data. If i turned the pot a little bit more, only the background was getting darker. I have a salvaged TS screen from a broken CFAG320240CX-TFH-TTS i had and put it on my test screen to see if the TS may be the problem. Its still a lot better than the TS one...

The screen will be at approx. 3 feet from the operator and at that the distance the faulty display is barely readable. Without the backlight its even worst. Im not convinced that it might be a lighting issue . Both have a contrast ratio of 5 in the datasheet but you can clearly see theres a big difference in the pictures. If its the normal operating contrast for this screen, i will admit, im kind of deceived.. Should i return this unit for test/repairs?

Thank you!

Jo

 

[jon_co]

Im starting to think that the polarizer might be the problem. I get the best contrast by viewing the screen with an angled view (1-2 o'clock position) to the left. If i try to view the screen with the same angle but from the right side the contrast is definitely lighter.

 

[Fer]

hey, did u use a PIC to control this one? i have a CFAG320240CX-TMIT and i want to graphic the ELECTRO CARDIO GRAMA on this, i will use a PIC16F877 or some PIC like this. do you have a code on CCS? thx a lot