Join Date: Dec 2002
Location: Saint Louis, Missouri
Re: Bench testing my AM radio
I can't help with the wiring but definately know which wire is what before connecting it up. I would also add an inline fuse to the power wire while testing. The size, maybe a 10A.
As far as a speaker grounding itself some speakers relied on the mounting of the speaker to take care of the negative terminal on the speaker. If the speaker had one wire connected to it you need to run a jumper wire from the frame of the speaker to the chassis of the radio to complete the circuit.
Chances are a terminal on your radio was "Y"'d off to where one wire went to ground and the other to the negative on the speaker.
To bench check the radio you will need some type of antenna. Without it you may hear some background hiss when the volume control is turned way up but since AM relies 100% on an antenna you need something to check for a signal. The test antenna doesn't have to be pretty but take a chunk of 16-18 gauge insulated stranded wire (like a speaker wire) and remove about 1/2" of insulation from the wire end. Carefully insert it into the antenna hole in the radio chassis to where the bare wire hits the center pin connection in the hole. Have the chunk of wire maybe 35-40" long and positioned vertically if possible.
Once you get it back into the car there is probably an antenna trimmer screw either on the chassis of the radio or behind the tuning knob. This is to match up the antenna to the radio. You tune to a weak station up high on the dial and then turn the screw one way or the other until you get the loudest output from that weak station.
1974 Spirit Of America Nova (being restored), 1973 Nova Custom, 1968 Chevy II (Garage Find 2012)
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