Couple of pointers ;

To measure the voltages from the power supply board, remove J1 and J3. Set the voltmeter to DC and connect the black probe to ground.

TP1 = 5Vdc
TP2 = 230Vdc
TP3 = 12Vdc
TP5 = 43Vdc

Change the meter to AV

TP4 = 7.3Vac

With the game off, remove the fuses and test each of them. Check the fuse holders, are they weak and brittle ?

If you have physically swapped the power supply and transformers, then you need to check the input voltage either at the varistor or E1 and E2 on the board. Sounds to me like a bad input voltage or gound. But if you are doing the tests with J1 and and J3, then something is dragging the voltage down.