The on/off switch is bad on the 6V A supply side. There is no continuity when the switch is on. The dial lamp side is fine. Can I 'join'
the 6 v lamp side to the A supply side to get 6V to the radio transformer. Thanks What is the purpose of the spark plate?

Yes, you can "join" the switch functions . . . I have done that in the distant past. Of course, the switch will be working extra hard, but should be good for a while.

The spark plate is just a low-inductance bypass capacitor on the battery feed line used to keep ignition noise out of the radio. The spark plate often is used in combination with a series inductor and conventional bypass capacitors.

Thanks. I have tried to join the two into one and the radio did play. I was worried that some other voltage or amperages might harm the radio for a customer. I did find another such radio but it too had some items installed to make it work. That repairman installed a 15 ohm resistor at 10W to the primary of the transformer from the switch.

I "joined" the switch functions in a Dodge radio years ago. In the original design, the radio dial lamp would only turn on if the dash lights and the radio were both on; the dial lamp dimmed with the dash lights.

When I joined the switch functions I used the "radio" supply side of the switch to feed both the radio and dial lamp. I left the power feed from the dash lamps (going to the lamp side of the switch) disconnected. Now the dial lamp goes on and off with the radio and is independent of the dash lights.

When I finger touch the tuning shaft the volume goes up loudly. What should I fix or repair?

Found the problem. A capacitor from the first 6BA6 to ground needed replacing.