While browsing a thrift store in Boulder, I found a great deal on a shower radio. I picked it up, figuring any problems with it could be fixed. The model is SR-25.
I got home and put in four AA's, and nothing happened. Time to open it up! It was closed via six screws under pads on the back.
Inside the radio. Note the clear plastic speaker.
After some testing, I determined the problem was with the clock/timer module on the front. This also controls the power to the radio but the whole thing was not working for some reason.
The clock/timer was connected to the main radio board with a ribbon cable. Luckily the pinout was labeled and I discovered that the radio turns on when the battery voltage is applied to the power pin.
Clock ribbon cable pinout
Now I just needed a way to control the power. The default power button is a momentary tactile switch, so something new is needed. First I tried to use the volume control knob, but I couldn't get that to work. Then I looked at the AM/FM/TV tuner selector switch and notice that only half of it was used.
AM/FM/TV tuner switch
I decided to use the unused half of this switch, although it would limit the radio to FM only.
Switch wired in
Now when the switch is set to the middle position (FM) the power is given to the power pin from the batteries.
As a bonus, the TUNE light still works because it is separate from the clock board.