I would look closely at the t (tilt) relay first. Make sure it operates by moving any tilt switch.Make sure the relay is actually making contact,ie...switch is making contact and clean.Coil on switch stack is actually good.Might us a meter just to make sure switch is closed.
Also make sure the closed slam switch is making contact
Dirt can be a real problem with any machine,especially one this old.
If all is Ok,then move to b/sb switches.
I'm guessing o manuel with machine so no start up sequence.
Let me know by PM if you need more help. I have a Gaucho.