Guitar wiring problem?

Question

I have just recently purchased a prewired pickgaurd for a strat. I finished attaching the input jack wires and I also attached the ground wire to the bridge (all with solder). The cavity of the strat is sheilded with copper tape, and the wire going to the bridge was too short so I attached another wire to it in order ti make it longer.

Now I get terrible feedback.

By chance is the extra wire causing interferenece?

Answer 1

the  solder is actting as a feed you may need to remove it and get some  solder for brass try it you may find it to inprove as the it will make some change look for the solder there are many out there

Answer 2

What you called feeback is actually 60 cycle hum.  The note you added to your question tells me the wires are probably reversed.

The shield, or braided wire to the amplifier is the ground wire.  It needs to be connected to the ground of the guitar, and the pickup ground, or body.  

The center wire for the amplifier cable is the hot wire and should go to the sound pickup output only, or to a volume control if you have one.

I think this should get it going for you.