CFAG12864 Backlight

[Fuente]

Hi,

I purchased 100 displays CFAG12864B-TMI-V from Crystalfontz. I'm having some problems with backlight of this displays. I use a BC807 (45 V, 500 mA PNP general purpose transistor) to drive the backlight. Some displays (about 30) have poor luminous intensity. I try drive 5V directly and the intensity does not increase. I need help do solve this problem.

Thanks..

edit by admin: added transistor parameters and link

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[CF Tech]

What is your complete backlight circuit? Is there a current limiting resistor?

 

[Fuente]

This is the complete circuit:

 

[CF Tech]

I think R30 is a bit small. The module is rated at 60ma. Assuming that Vcesat for Q13 is 0.2v:

R30 = (5v - 3.5v - 0.2v) / 0.060 A = 21.67 ohms