powering a spring reverb

[dylar]

This is an odd issue...
I'm building a super lo-fi spring reverb unit, and I'm using the innards of an old boombox to power it.  So far it works great--the spring is attached to the speaker with hot glue and you can already hear the reverb loud and clear when the radio is playing thru it (going to use piezo transducers to pick up the signal--waiting for them in mail).  My problem is with how to get a signal going into the boombox amp.
The boombox does not have power switch.  Instead, there is a switch that allows you to select tuner or tape.  When the tuner is selected the amp is on, but the tape selector doubles as a power off (the switch to select tape or tuner is right in the lower-middle of the second pic).  I assume that when one of the buttons on the cassette is engaged it closes the circuit and sends power to the amp.  However, I can't see where this happens.  Would it be better to send my signal through the tuner in, or is there a way to permanently close the circuit so that when I select the tape option the power is always on?  

whole thing


closeup of boombox board


cassette module front


cassette module back

[JKowalski]

Ahhh

Confusing

Trace the power voltage into the switch and find out what lead it connects/disconnects to when the switch is hit. Bridge it. We can't see the bottom of the board, so we have no idea what that switch does. You are your best bet here.