The list of things to check starts with the mike.
Do you have a way to test it, like by trying it on another radio?
Do you have any way to tell if the radio is transmitting, like an inline meter in the antenna coax?
There is a LED on the face of this model. It will be green while receiving, and turn red while transmitting. Does this LED do anything? This is a built-in diagnostic feature. Ignoring it puts us all in the dark.
Does the meter on the front of the radio move when you are receiving other stations? Does it move when you key the mike? If that LED simply goes dark when you key the mike this meter will simply fall to zero, at the left side of the scale.
The antenna can fail and allow you to hear strong stations, but still disable or BREAK the transmitter section of the radio. A defective antenna, damaged coax cable or connector can blow out the transmitter's power section.
If your car won't start, you begin by identifying the systems that are needed to make it start. Seeing that it has fuel, that it has compression, that it has spark are all a part of this process.
The radio is not all that different. If you can't tell a broken antenna or mike from one that works, this is a tremendous disadvantage.
A mechanic who doesn't have a screwdriver to unclamp the fuel line and check for pressure will be handicapped in a similar way.
Oh, one last thought. Did you change the mode knob from AM to either "USB" or "LSB" and try to transmit. This radio can fail on AM transmit only, but still transmit on the two sideband modes. Seeing the result of this one, simple test can be tremendously informative.
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