Don't over-look the simple stuff

Have a "dead" transistor radio (no sound)?? Before you get too crazy pouring over schematics and disassembling everything to make voltage checks--check this first--does the radio have a earphone jack????

Many times dirt and corrosion upset the tiny make/break contacts inside the earphone jack. This prevents audio from reaching the speaker. Carefully use some plastic-safe electronic cleaner and work the contacts back and forth with a earphone connector. You may even have to scrape the contacts with a sewing needle to get some conductivity back.

Just a hint.

I have had that happen on a Toshiba.

I have found this to be the case on several radios and is one of the first things to check right after the battery.

I've put a post up about jack maintenance on the tips forum also.

Back in the 70's i used to buy hundreds of transistor radios through thrift shops and flea markets to fix resell & collect . Many of the pocket radios , they put the earphone jack right next to the battery . If that arm on the jack was installed up it was pretty easy for heavy handed people to push the battery against it in a rush to get the battery replaced and slightly bend that arm down disabling the speaker .
Many radios i fixed in the back seat on the way home ( i was a wee lad )