I have found out the hard way that even if you value your labor at minimum wage, its money ahead to have a “radio road map” or schematic:

https://autoradioschematics.com/

You can also search eBay of “Sams Photofact”
with your radio model number.

Most shade tree fixers have some sort of multimeter,
and even the “give away” Harbor Freight meters have built in Transistor Tester
and “Diode” position on the switch,
but require desoldering and isolating the suspect part.

The component that most often goes bad in old radios is one of those small cylindrical pill bottle shaped “electrolytic capacitors” .
Some times you can immediately spot bad ones because the top is swelled out, or leaking goo.

If the cap looks normal it still can be bad,
and here a great time saver is the
ESR Meter (equivalent series resistance)
which can good/bad test an Electrolytic Capacitor in place with no de-soldering.

Some experienced repairers advise: First thing replace all Electrolytic Capacitors, period.

If you want to go with the pioneer of such testers, higher $ and still highly respected:

https://www.amazon.com/Peak-Electro...ee2c297&pd_rd_i=B005NIBEYU&psc=1

These ESR have become very cheap from China and most have added digital features,
such as the widely sold GM328 (or similar number)
which you can scroll down and read about here:

https://childhoodradio.com/test-equipment/