electric guitar hum

i know very little about electricity, or electric guitars in particular, so naturally, i bought an electric guitar that needed a new pickup assembly. i bought it, put it together and plugged it in. i can get sound,but i get a horrendous hum. the hum goes away when i touch the assembly for the jack on the guitar where the cord goes in.
it is an ‘arbor’ brand guitar, so i don’t want to spend any money taking it to get it fixed. so far it has only cost me 30 bucks, and for an arbor, that is enough.
what can i do to fix it?

Sounds like a grounding problem. Did the new pickup have a ground wire? Did you solder it to a ground contact on the guitar. Also what kind of pick up; single or double coil?

Sounds like you have a floating ground. Check to be sure the ground pin on the amp’s power cord is there, if it’s broken off, you’ll need to replace the plug. If you’re got it plugged in using a three-prong-to-two-prong grond adaptor, be sure to remove the screw in the wall plate and pass it through the grounding tab on the adaptor and screw it down tightly. If none of thses things fixes the problem, then the float is inside the amp.

You said you “bought and put together” a pickup assembly. To me it seems something might have gone wrong there too - unless it was pre-wired. I’d like more of a description of what the pickup assembly consists of and what you had to do to install it.
As others have said it seems the ground connection on the guitar is faulty.

(I’ve been playing and rewiring guitars for decades now - and boy are my arms tired).

oops…just back from work.
just sort of answering you all helter skelter…
it was prewired…i just meant that i hooked 2 wires on. one that i thot was the ground and the one to the to the jack.
i think it is a single coil.
i shall try out all of this good info tomorrow and will get back with you all.
(good one, wolf)

Single coil guitars do suffer some inherent hum. However they should have a ground wire that goes to the bridge of the guitar, that way when you touch the strings the hum should go away (mostly). You can also put aluminium tape around the pickup cavity and underneath the pick guard, this should help cut down on the amount of radio interference the electrics pickup.

skogcat, yes single coils do have a hum problem but handsomeharry says the hum is “horrendous”. Again, the wiring might be messed up. How’s the connection at the guitar output jack ? Are both leads well-soldered and is the polarity correct?