5p8 connector off transformer is for solenoids....goes to 5j8 on the Aux board at Fuses f7 and F8. So check the incoming AC at the fuses. You can't check AC to ground as the secondary isn't bonded, so red lead on the fuse clip F8, black lead on 5j8 pin 3. Then Red lead on F7 and black lead on 5j8 pin 8. If those are both reading higher VAC, then check DC F1, F4, F3, F6 and F5 for Voltages to ground. F4, F5, F6 apx 50 to 70vdc, f1 and F3 apx 25 to 40vdc.

For GI, connector 7j3 at the transformer. Yellow wires as mentioned above. They connect to the interconnect board at 2J6. On AC, check Fuses F1 to F4, against pins 1 and 3 on 2j6. If AC is good, then check other side of fuses F1 to F4 DC voltage to ground.

Attached Schematic for reference

taxi (resized).jpg