Jaguar buzzing/humming and microphonic selector switch - normal?

Philtre

Just started playing my AV 65 Jaguar again and noticed a louder than normal electrical buzz when not touching any metal guitar parts or strings. Also, when the bridge pickup switch is turned on, the selector unit and the three switches are microphonic if I tap them with a pick.

Is this normal and I just haven't noticed it before, or does it indicate an earthing problem inside the guitar's electrics? The guitar was brought new last year.

thermionic

I had a similar problem on mine, but at the rhythm circuit. One of the rollers was microphonic in the exact way you describe. I can’t remember exactly what the cause, but some terminal was bent and shorting to something else. All I did to fix it was open it up and bend it back.

Philtre

I've opened up both switch units and can't see anything unusual. Also tested ground continuity between all metal parts with a meter.

@thermionic if you engage just the bridge pickup switch and tap the switch do you get any noise?

ICBM

I have come to the conclusion that this is definitely the month for buzzing guitars. Probably something to do with Dry January not allowing the static to drain away naturally or something...

Philtre

Hmmm...actually it's not the switch or switch unit that is microphonic. I lifted the switch unit out of the guitar and tapped it and no noise. However, tapping on the pickguard gives the microphonic sound. So I guess it must be the bridge pickup. Strange thing is that tapping on the pickup body itself doesn't give the noise.

ICBM

Philtre said:

Hmmm...actually it's not the switch or switch unit that is microphonic. I lifted the switch unit out of the guitar and tapped it and no noise. However, tapping on the pickguard gives the microphonic sound. So I guess it must be the bridge pickup. Strange thing is that tapping on the pickup body itself doesn't give the noise.

Not if tapping on the pickup doesn't do it - assuming you have definitely got the pickup selected!

Tap everything else until you find it - the tone cap is actually a possibility, surprisingly.

Philtre

OK, tapping on the tremolo arm and tremolo plate gives the sound.

thermionic

No, never had any problem with the lower switch panel. My problem was confined to the volume (or tone, I forget) roller, no other parts were microphonic and I was able to narrow down the problem area. If all three of your switches are microphonic maybe it's something common to all three - ground, or something touching the metal plate?

Philtre

@octatonic Thanks. If you turn off all three selector switches and don't touch the guitar do you get hum?

Philtre

Right, I know the cause of the microphonic sound when tapping parts of the guitar when the bridge pickup is on. I took the pickguard off and it cured it. So I saw that when the pickguard is on it fits tightly on and touches the bridge pickup. So tapping on the various parts of the guitar was indirectly tapping the pickup. The neck pickup has a gap around it and the pickguard so that's why it wasn't affected.

At least I now know how a Jaguar is constructed.

ICBM

Philtre said:

Right, I know the cause of the microphonic sound when tapping parts of the guitar when the bridge pickup is on. I took the pickguard off and it cured it. So I saw that when the pickguard is on it fits tightly on and touches the bridge pickup. So tapping on the various parts of the guitar was indirectly tapping the pickup. The neck pickup has a gap around it and the pickguard so that's why it wasn't affected.

At least I now know how a Jaguar is constructed.

If the guard is touching the metal 'claw' on the pickup then it may be that the claw is loose on the bottom of the pickup - they're notorious for this. I thought that you'd eliminated the pickup if tapping the top of the cover didn't do it, but it may just be the claw. To fix it, you need to heat the claw so that it re-melts the wax that's supposed to stick it to the pickup. Do it with the pickup cover removed so you don't overheat it.

Philtre

@ICBM I don't think it's that, but rather that the pickguard is a tight fit around the bridge pickup. I just nudged it a bit to give it an air gap.

All I need to do now is figure out if there should be a hum (unless you touch a ground point) when all three switches are off, or the mid-tone switch is up.

All three switches down - hum.

Any pickup switch up and tone switch up - hum.

ICBM

There is always a little hum (or more accurately buzz) from any passive electric guitar when you're not touching something grounded on it, even when it's thoroughly shielded.

Philtre

ICBM said:

There is always a little hum (or more accurately buzz) from any passive electric guitar when you're not touching something grounded on it, even when it's thoroughly shielded.

Right. But I just wonder why it really hums/buzzes when all pickups are disengaged and a bit when the tone switch is engaged. Maybe I've just not noticed it so much before.

ICBM

Philtre said:

Right. But I just wonder why it really hums/buzzes when all pickups are disengaged and a bit when the tone switch is engaged. Maybe I've just not noticed it so much before.

It buzzes more when both pickups are off because it's then an open circuit at the volume control input - this is a design fault with the Jaguar. (And Mustang.)

The tone switch is a cap which partially isolates the pickups from the volume control so the same happens, but less.

Philtre

@ICBM Thanks. I think that explains it. I guess I noticed it more today because next door were out and I had the amp wound up for a change. ;-)