15 R3, no boot black screen, 2 blinking red, 7 blue, #2

2,7 is a display failure (or more correctly that the system doesn't recognize the display).

Can you get a display self-test to run (hold the D key through the powerup cycle and a series of self-test patterns should appear)?

The power and battery-status light blinks red and blue along with beep codes indicating failures. For example, the power and battery-status light blinks red two times followed by a pause, and then blinks blue three times followed by a pause. This 2,3 pattern continues until the computer is turned off indicating no memory or RAM is detected. The following table shows different light patterns and what they indicate. Table 1. Diagnostics Light Pattern Problem description 2,1 CPU failure 2,2 System board: BIOS and ROM failure 2,3 No memory or RAM detected 2,4 Memory or RAM failure 2,5 Invalid memory installed 2,6 System board or chipset error 2,7 LCD failure 3,1 CMOS battery failure 3,2 PCI/video card failure 3,3 Recovery image not found 3,4 Recovery image found but invalid