Semi acoustic guitar help, please.
 

When my son tries to play his guitar through an amp (a known working amp, with a working lead), it doesn't, err .... amplify! I unscrewed the little equaliser bit and replaced the battery. 'still didn't work.
I checked the wires that ran from that item to where the lead from the guitar (to the amp) gets attached, and they seem OK.
Does anyone know how I can test this bit? Can a replacement be readily sourced? What is the correct name for the bit/s about which I'm talking?
He wants to replace the guitar - I said that I don't replace my car everytime it needs a bit of TLC! (He's an end-of-1st-year university student, and is secretly hoping (as I see it) that the bank of mum and dad will spring to the rescue).
So any advice will be gratefully received. TIA.
Stephen

It's possible that the Piezoelectric pickup isn't piezoelectricing.

I assume it's turned on?

Start with the Instrument cord, then the cord plug in the guitar. They are the first to go. Especially if it was a used guitar, with drinking players stepping on the cord will in use. A little solder if bad. Check pick up wiring and signal.

Are the strings nylon (gut).

Now THAT'S funny.

My "guess" would be the cable or the jack on the amp or guitar.

I think son may have disabled it so you can buy that new Gibson ES 335 for him.

Thanks for the replies, folks. I'll try to sort it.
Stephen