These are some of the common faults I have found over the years.
1. No Sound:
Look for open coupling cap to volume control. Also check the earphone jack. The switching contacts get dirty or bent. plus dead battery or it has come out of the holder and contacts not making.
2. Battery dies quickly or gets VERY hot: There is a cap across the battery leads (decoupling) after the power switch. They short. (This is true even in remote controls, and I have seen it in car radios also).
3. Motorboating: See
[You must be registered and logged in to see this link.], same solution. Also can be main filter caps.
4. Volume control very scratchy: Clean or replace control.
5. Volume won't turn down: Look for bad ground off the volume pot.
6. Dead: See
[You must be registered and logged in to see this link.].
Look for bad batteries or leaking batteries that have corroded the battery contacts. If alkaline batteries, clean contacts with white vinegar, clean water, & dry.
Note: Don't always believe the customer when they say " I just put new batteries in the radio a couple of weeks ago". 95% of the time the batteries were put in there months/years ago, and are dead/leaking.
Also some brands of batteries are just plain crap. I saw brand new batteries for flashlights that only worked for 1-
2 minutes before failing, being sold to the State of Washington back in the 70's . Purchasing for the agency refused to get good quality ones. Test all "New batteries" before installing. New does not in any way mean they are good batteries.