120hz buzz from Fender reverb footswitch - only when on floor?!

[Pixel]

Hey everyone, I got a really strange problem with my BF Deluxe Reverb.

I get some nasty 120hz buzz (spikes at 120hz) coming through the reverb - but only when I have the footswitch laying on the ground.

I know the footswitch is a terrible design, sending the low-voltage signal through the shielded cable to the switch itself. I tested the shield, checked the wiring in the switch (outside metal is tied to shield), checked the amp inside - no issues. I even tried it in different parts of the house.

If I hold the switch in the air the buzz is reduced massively (even with rubber gloves, so not grounding the footswitch through my body) and gets worse the more cable is laid on the ground.

This is with the original fender footswitch, but I also tried a few aftermarket switches with TRS jacks and cables - those were even worse (probably because the TRS cables were way longer than the original fender footswitch).

This is with no guitar attached, dead silent amp otherwise - 3 prong connector, new house with proper wiring. Tried multiple tubes in the reverb recovery circuit, tube already has shield.

Any guesses?

Is this a new problem?

Does the amp have this problem anywhere other than your house?

[g1]

Does the amp have this problem anywhere other than your house?

See posts #5 and #7.

[Chuck H]

Wow! Somehow I totally missed post 7 in my last couple of posts. So, since changing anything about the house that might be causing the problem would probably be more costly,.. Yeah, try shielding the bottom of the pedal.

[Pixel]

See posts #5 and #7.

Sorry, my question was poorly worded. Was trying to see if there was a problem if the amp was plugged into a completely different power source, ie at another house/venue.

[waspclothes]

So last night I tried a few more experiments:

1. I turned off every breaker in the house off, except for a single plug. The buzz was still happening with the reverb pedal on the floor, and anywhere in the house.

2. Instead of the reverb switch, I can also use a single-coil guitar and laying that down on the floor results in the exact same buzz.

3. I also tried a different amp, same buzz if I lay the guitar on the floor.

4. I can also just use an oscilloscope probe and see the buzz if I put the probe against the floor.


I know I can add shielding to the bottom of the footswitch to reduce this, but at this point I'm way more confused than anything!

We just moved into this house, it has an insulated poured concrete slab with electric heating elements inside. I don't live in a city, the next house is 300 feet away, overhead power lines are 120 feet away. there are high voltage overhead power lines about 1200 feet away. My friend had a theory that maybe the loops of wiring in the underfloor heating were inductively picking up RF from the high voltage power lines, and he spoke with an engineer at the hydro company - who said they're much too far away to cause a problem.

[Helmholtz]

Induction would require a magnetic field caused by current.
As the problem remains with the heater current turned off, I would exclude magnetic induction from the heater.
But neither concrete nor the ground below are perfect electrical insulators, so they the will carry and spread electric fields due to voltage.

BTW, shielding does not help with magnetic fields.

[Pixel]

So last night I tried a few more experiments:

1. I turned off every breaker in the house off, except for a single plug. The buzz was still happening with the reverb pedal on the floor, and anywhere in the house.

That reminds me of when I used to help a friend with his home automation business. Often there were problems due to electrosmog or dirty power. So troubleshooting usually involved turning breakers on and off to isolate problem areas. The most interesting problem I found was after tracing a power line to a garage. I saw the line go from the house to an underground conduit, into the garage, and hold on...out of the garage again, under the ground, into the neighbour's garage. Turns out the neighbour had been stealing power for quite a while. The neighbour tried to say it was done before he was the owner, but the wire manufacturer provided info that the cable wasn't made before he was the owner.

I'd still be interested to see if the amp is okay when used with another power source like a different house or a UPS.

[loudthud]

I lived in a rental house that was built with Aluminum wiring. Most of the outlets had three wire receptacles with the ground not connected to anything.

[Chuck H]

I lived in a rental house that was built with Aluminum wiring. Most of the outlets had three wire receptacles with the ground not connected to anything.

Charming. I'll just bet it wasn't code for the year it was built. Though I suppose the three wire recepticles could have been newer and replaced older two wire units.?. But with aluminum wiring that seems unlikely. Hard to say but I get the impression it must have been the owners DIY handywork or done by some hack they hired for cheap.

[Tom Phillips]

I lived in a rental house that was built with Aluminum wiring. Most of the outlets had three wire receptacles with the ground not connected to anything.

wow. Does that mean that there were aluminum wires connected to copper push-in or copper screw contacts?

[nosaj]

Charming. I'll just bet it wasn't code for the year it was built. Though I suppose the three wire recepticles could have been newer and replaced older two wire units.?. But with aluminum wiring that seems unlikely. Hard to say but I get the impression it must have been the owners DIY handywork or done by some hack they hired for cheap.

During the 70's aluminum was tried out for a while in the builder category(copper inflation?? IDK I was still a kid).
Our first house was wired aluminum when i replaced outlets I has to make sure to buy the correct ones for al/cu so you didn't end up with a galvanic reaction an start a fire.
nosaj

[Chuck H]

During the 70's aluminum was tried out for a while...

Well I knew that I never saw it in really old houses and I knew that grounded AC regulations were already in effect by that time. So it seems whomever wired LT's old digs was skirting safety regulations.

And I too would be interested if the recepticles had copper connectors. It seems likely since, well, screw the regulations already, right?