Volume Problem

[mooseling]

Hello,

i'm not very well versed in any of this stuff, so forgive me if I don't fully understand what i've done.
I've been building a pair of iPod speakers out of an old boombox. I took the boom box apart and removed components until only the motherboard and speakers were left. I've wired a headphone jack onto the cables which used to connect the tape deck to the motherboard. I've also removed the power supply chip and wired batteries onto the cord that it used to use.
Now, I've been playing music on it fine, but now and then the volume jumps really loud. later it will jump back to its previous setting. it seems to do this repeatedly, but less frequently as its been playing for a while. i do not understand much of what the chip actually does, so I wouldnt know if there was a problem there.
Any ideas?