Start Dating fender pickups and pots

Dating fender pickups and pots

Each style of bridges functions differently and is set up differently.

Lacking a mains transformer, the chassis of the AA5 radio was directly connected to one side of the mains electric supply.

Therefore your guitar strings will also connect to this circuit.

I can personally attest that the resistor and capacitor will not protect you from a truly nasty shock. If it wasn’t plugged in in the “right” direction, i.e., if “ground” was 117 volts) then when your lips touched a grounded microphone it hurt. I suppose if you didn’t jerk back or let go of the guitar, and kept your lips on the microphone, and you were married, and if the capacitor was bad, it could produce a widow.

The tube heaters on these are wired in series to effectively reduce the wall voltage (it’s spread over their resistances), and the tubes are not your typical Fender-type tubes, which cannot easily operate this way.

For a schematic example of this type of amp, see the Harmony H-400: In this example they used a small transformer for the heater of the 12AU6, but the 50C5 and 35W4 heaters have no transformer isolating them from the wall outlet voltage.

The hazard was made worse because the on/off switch was often in the wire of the mains supply which was connected to the chassis, meaning that the chassis could be “hot” when the set was either ‘on’ or ‘off’ – depending on which way the plug was inserted in the power outlet.

The metal chassis securing screws were often accessible from the outside of the Bakelite or wood case, and there were many examples of owners receiving a shock by making contact with these screws while handling a set.

Those circuits were adapted by many low-cost guitar amp makers.