strange noise in my amp, please help!!

[sufick]

I have a guitar tube amplifier 60W (fender devile 410), connected to the guitar, lately I hear the sound of constant frequency electric pulse of approximately every 0.85 sec
Tests I have made and nothing helped:
1. I changed - a new amplifier, cable, guitar
2. I hooked up the neighbor's electricity
3. I ordered an electrician and inspected the ground and found no problem
4. I added a voltage stabilizer
5. I hooked it to a neighbor and still there was noise
6. I took the amp 20 meters from the house with an extension cord and it did not help
7. when the cable is not connected to the amp - there no noise
• I turned on the amp with the guitar somewhere else and there is no problem (in another place of residence)
I made all attempts I concluded that this noise is received from outside, from something a transmitter, when I stand with the guitar and I turn around there is only two quiet spots 180 degrees away from each other) But I have no idea what that means, I do not know which direction to look for - mobile, a magnetic field ... I do not know who to turn to, if anyone has any idea I would love very much, I can not play please help me ...

[Gibsonman63]

On number 7, I presume you mean the instrument cable. If that is the case, the problem is probably in your guitar and not the amp. Try a different guitar with humbuckers. Some single coil equipped guitars are hard to get the hum out of, but there are lots of threads here on grounding and shielding schemes for guitars.

[Jazz P Bass]

Yeah, if the guitar is single coil, you will "pickup" (pun intended) all sorts of extraneous stuff.
Turning 180 degrees just verifies the "null" point of the pickup field.
Push comes to shove you could try a noise gate pedal.
When there is no signal from the guitar, it turns off the output from the guitar.
As soon as you strike a note, the gate will turn on.

[J M Fahey]

Stand on a corner of the "haunted" room, turn 360º and mark both nulls, then trace a line in the floor (or use a broomstick or similar) to point 90º from nulls.
Repeat in 2 or 3 corners.
All lines should cross somewhere, maybe outside of that room.
That's where the noise comes from.
It might come from another room, in that case repeat the experiment there.
I once had a zzzt zzzzzttttt ZZZZTTTT TICK TICK TICK ZZZZTTTT zzzztttt zzt ... silence for 15 seconds ... repeating the sequence on and on.
I heard it *everywhere*: amplifiers, TV, radio, even the telephone.
They were testing full power (illegally) the radar from a Spanish fishing boat, 100 meters from my house.
I live in La Boca, the ancient Buenos Aires Port, today a touristic attraction.

[Enzo]

And when you are playing this guitar, do you have a cell phone on your person? Try turning that OFF just to see.

[Ronsonic]

7. when the cable is not connected to the amp - there no noise

Then it is probably not an amp problem. Plug a short cable and guitar in, turn the guitar volumes to zero. If still no noise, it isn't the amp.

[Jag]

In addition to what Enzo said, take your watch off.