What do you read for voltage at the different points in the regulator circuit? (I'd mark up the diagram I included previously, or the PCB layout, whichever is easier, with the volts you read at each point in that diagrammed circuit). It may have just popped Q1, or maybe D3.
If there is no voltage at the D3 output but is at the input, then D3 is probably popped, and you can use the diode test on the multimeter (with no battery connected to the CA) to test it.
If there is battery voltage at D3, then R24 should have battery on one side, and about 9v on the other, where it connects to Q1 and the zener Z1. If it does, then Q1 will turn on and work. If not, Q1 won't do anything.
If Q1 is working it will have about 12v on the output at C5. If not, Q1 is probably popped. Q1 is a "depletion mode" FET, there's details on what can be used to replace it in the CA repair thread in Justin's posts.
Do you have a 12v supply available? If so, you can connect it to the Q1/C5 junction, that leads to the LED backlight supply input. The CA will power up, but probably show LOW VOLTS right after the boot screen. If so, the MCU is probably ok. This means replacing Q1 would probably fix it, if you have the 9v at Z1/R24.
WIth that 12v supply connected, If the CA doesn't power up but the backlight comes on, and a meter does show 12v at the Q1/C5 junction, the MCU may be toast, or the 5v supply to the MCU might be. I don't have a diagram for any of the power supply or CA other than that small section of the input above.