Once I determine the radio's model number/part number, thru on line radio service information sources (sometimes free or at a nominal download charge, via a PDF file) in the form of a schematic diagram. Print the PDF file. I personally have a RF signal generator, that can introduce aa RF signal (either AM or FM) modulated or not, into to the radio, to simulate a broadcast station or just the carrier wave and thru the use of my signal tracer and oscilloscope trace the injected RF signal BACKWARDS from the output (speaker connections) thru the various amplifier stages, thru the detector circuit, thru the tuned Intermediate Amplifier stages (IF), local oscillator & RF amplifier stages (dial tuning stages) thru and including the injected signal......nothing to it.....just like reading (and understanding) a road map, to locate and replace the defective component....transistor or resistor or capacitor. I can fix both AM and FM radios but not Stereo FM, as I do not have the FM stereo frequency generator accessory. Howard W. Sam's is a great source for service info and their service information shows pictorial views of the radio's components to help ID the various parts and their location. Sam's information shows part numbers, values, alternate values and how to align and reset all tuning/tuned stages. Power the removed radio with a good battery charger that can supply either 6 volts or 12 volts. .......just like installing a new cam....no big deal......just my option......
BOB RENTON