I've just whipped up a schematic using some fancy CAD software.....
I am wondering if my problem lies with the "-" speaker input - does this need to go to the earth for the potentiometer?
Yes, did some mucking around with an old radio 1st.
Currently i am using a 12v battery sponsored by work as a power supply, but intend to use the 12v source at the coin door interface board (from an Indiana Jones - some other guy has done this (http://www.edcheung.com/album/album06/Pinball/ij2.htm - at the end of the page).
**Just looked at my diagram and the pot numbers should be reversed ie: 3 at the top and 1 at the bottom**....dodgy software!!
first try disconecting the ground from the pot to the cab earth: if this solves your problem then try hooking the pin you had from your pot to cab earth to the spk -
make sure that you have the 100k resistor in line because if you dont when you turn the pot to the volume low side you will be shorting the output of your pin amp to ground and will probably fry some components on the sound board.
Remember electronic components are like a genie in a lantern, once the smoke has escaped neither of them will work
