How do I measure output voltages at Tristar?

When measuring voltage rails, they are all done in the same manner. So if you are successfully reading VCC_MAIN and BATT_VCC for example, the same method will apply to reading PP6V0_LCM_BOOST. Now obviously, you have to insure you are probing the correct side of the capacitor (not the ground side).

Some rails don’t give the expected voltage under passive conditions, such as a logic board connected to battery only because the power IC is waiting for some kind of timing signal or feedback loop. A good example of this is the ANODE line, it will only read the same as VCC_MAIN unless it detects a screen, in which case it will boost the voltage.

Unfortunately, without seeing you in action, I can’t really say if you are doing something wrong. It may be that you are probing a dead circuit and that it is “normal” that you aren’t reading anything. Check on constant rails such as PP_CPU to see if you can measure some voltages.