My brother has an electric guitar which he has not played or even touched for at least fifteen years. It's a cheap strat-like guitar, equipped with three unknown (most likely stock) single coil pickups. Last weekend I was visiting him and he gave it to me.
When I got home, I plugged it into my amplifier and it started to make a very loud buzzing noise. I noticed that the noise is significantly reduced whenever I touch some metal parts, such as the bridge or the input jack. As suggested by this question and many other references that I have found during a quick research, this scenario suggests grounding issues.
A quick note: I have been playing guitar for many years now, but I never tried to fix the problems of any of my guitars - I have always handed them to professionals. Since this is a cheap and old guitar, I figured this would be a great opportunity to learn a bit of guitar electronics and maintenance.
So yesterday I opened the guitar and worked on it a bit. Many components were oxidized; so, apart from checking and resoldering the ground wiring, I replaced the following components with brand new ones:
- All three potentiometers
- The input jack
- Every wire except the ones that come from the pickups
Still, the guitar is making a loud noise when plugged into an amplifier. I really don't think it's just a single coil hum, since it is way too loud even if the volume on the amplifier is low. Also, from what I have read in the past few days, the fact that touching metal parts basically cuts off the noise seems to suggest this is indeed a grounding issue.
I took the time to analyze the guitar wiring and made this simple diagram:
Is the wiring correct? While searching on the internet, I didn't find a guitar wiring diagram that looks like this one. Since I don't know much of electronics, I'm not sure if this guitar was already wrongly wired/grounded.
And in case the wiring is correct, what else could be causing the loud noise?