Sony Reader PRS-900 fonts are not dark

My Sony Reader PRS-900 fonts are not dark (blurred). I've searched forums to see any articles helps me to increase darkness of font. Nothing found. Service manual for PRS-900 is not available and other manuals refer to go to Test mode and there is no test mode software is available to download. Also, let me know whether you have lastest software to upgrade my PRS-900. Please let me know.

Thanks in Advance

Jay