Did you ever change a battery and then the preamp didn't work after that?
I bought an Aria Elecord FET 500 a month ago because it has a volume & tone controls. I didn't realize if you leave a cord plugged in it runs down the battery. Then I noticed there is no on or off switch, just a little unidentified button which I guess is to test the battery. There is a battery test light but it doesn't light.
So, I put in a new 9v battery and now it doesn't work. Hard to figure out how I could have possibly damaged it because the battery goes in a little case which you slip into the preamp housing. There is no way to put the battery in improperly because the slots for the + and - are different sizes. I tried contact spray, but it isn't corroded. This is practically a new guitar.
I guess the next step would be to unscrew the whole preamp and have a look at it? I'm just wondering if anyone has any experience with this model and I'm missing something basic.