1968 Factory Delco AM Radio Troubleshooting Guide?

[ShortCST]

I searched "Radio" and got 160 search results from the forums. Didn't find a troubleshooting guide. I ordered a new 8 ohm speaker from S&M Electro-Tech, and installed it.

No light on the radio, and zero sound. The sound went out a couple of years ago. Then the light.

I have a good digital multimeter, and I'm good at troubleshooting.

Is there a good troubleshooting guide available somewhere online for these radios?

Thanks in advance.