Also, check the bounce switches in the main cabinet. These are switches that have a round piece of metal at the end of the switch blade. There is one bounce switch that comes after the transformer in the primary power circuit and that switch needs to be in the normally closed (NC) position. You can check if you have power at the transformer with a multi-meter. Check if there is power at the 25 volt and 6 volt side of the transformer...

Also, you can start troubleshooting from the transformer. Check to see if there is power at the 110/120 volt side of the transformer - red wire and white wire. If there is no power at the 25 volt side and 6 volt side of the transformer, then there would be a problem between the 5 amp slo-blo fuse block - black wire - and the 110/120 volt side of the transformer. Check to make sure the power switch mounting nut is tight on the underside of the cabinet... It would be VERY unusual if the transformer was found to be bad...