I recently came into possession of a nearly new Fender Stratocaster Acoustasonic. When this guitar is jacked into my amplifier if the strings are touched it gives a loud unpleasant hum. I know there is nothing wrong with the amplifier as other guitars plugged into my amplifier work without any hum. Can someone please explain to me what the cause is, and how to solve the problem?
Has anyone been poking around the guts of the guitar? Swapping the wires to the output jack by accident will cause this very condition.

Also wouldn't hurt to make sure the bridge is grounded. You can do this with an ohm meter by looking for continuity between the jack nut and bridge. If you get a high resistance then the bridge isn't properly grounded and/or the jack wires have been swapped.
Last edited by Invader Jim at Apr 30, 2014,
Thanks alot for your prompt reply. I will get myself an ohm meter asap and check as you said. What exactly do you mean by jack nut though? I am unsure which wire connects to tip and which connects to sleeve, but is that relevant? Sorry, I'm very much a noob at this. And apologies if I started this thread in the wrong section.
If pictures will help please let me know.
I forgot to mention - the loud hum when touching the strings almost completely disappears when I also touch the volume knob or tone knob, both of which are positioned on the saddle. Does this mean it's the bridge not being grounded properly?
And as for anyone meddling with the guitar, I wouldn't know who did what to it before I got it. It looks new and undamaged, but that's all I know.
I meant the nut that holds the Jack to the guitar. The nut is in contact with the sleeve (ground connection) so you can measure continuity between the ground lug of the jack and other parts that should be grounded without having to take apart the guitar.

What do you mean the pots are on the saddle?

If you touch grounded metal parts and the noise goes away or is reduced, that's normal and indicates the jack is wired correctly. Sounds like the bridge isn't properly grounded. An ohm meter will tell for sure.