Fender Prosonic pop when something like a fan is turned on in my shop...

[tim]

This is a new one for me...

Customer dropped off a Fender Prosonic combo and said reverb was dead and that it intermittently popped, sometimes fairly loudly. Reverb problem will be cured by a new cable.

While the amp was on and turned up a bit, I just happened to turn the fan off in my shop and I heard a fairly loud pop come out of the speaker. I have repaired hundreds of amps in this shop and never have I heard this. I am beginning to wonder if he has something in his home that is causing the same thing that I heard.

Where does one start troubleshooting something like this? Pretty sure this is being caused by line voltage transients.

[TomCarlos]

A few things to consider....

It could be a near faulty switch in the fan that is arching when you turn it on and off. So, if you leave the switch in the "on" position and unplug the fan from the outlet, do you get the same result?

Next, I would check to make sure the outlet is wired correctly. I read somewhere about plugs being wired backwards and it created some type of noise issue (in amps, stereos, etc) when turning things on and off at that outlet.

What else is on that circuit? If you take the amp, run it through a LONG but adequate extension cord to another outlet on another circuit, then turn the fan on and off, do you get the same result?

Does this happen with other amps plugged into the same outlet?

If this is a new problem, something must have happened recently to cause this issue.

[Chuck H]

Can we assume you didn't have a guitar plugged into the amp and that the reverb cable is properly shielded?

[Enzo]

It is either coming in through the mains, or it is being radiated and picked up by sensitive circuits. SPikes can ride the mains. Switches on things like fans or furnaces or sump pumps or even the bedroom ceiling light can spark, and a spark radiates energy in the electronic bands.

Get a battery operated AM radio, tuned to between stations, and set it nearby. Does it pick up the fan switch?

Filtered outlet strips used to be real common for plugging in computers. Plug the amp into one of those to see if the line filter makes the difference.

[nosaj]

Can we assume you didn't have a guitar plugged into the amp and that the reverb cable is properly shielded?

One amp I was working on you could hear the Local BibleThumpers Am radio station coming in through the reverb pan and through the amp. Shield had broken at plug.
nosaj

[Enzo]

Well, the lord does work in mysterious ways...

[Justin Thomas]

Funny, my Prosonic once started blasting Neal Boortz in the middle of the sermon. Another reason to use the Standby switch instead of just rolling down your guitar volume.

Jusrin

[drewl]

My lab is on the same circuit as the son's massive sound system.

You can hear and see on a scope the voltage surging along to the beat.