Amps Hum in Blues Junior

[JPsuff]

When I turn on my Blues Junior IV all I get is a low-level hum.

No signal from the guitar and it's happening whether the guitar is plugged in or not.

I was playing through it the other night and I got sidetracked and put my guitar down with the amp still on and the guitar volume up (very low level, just noodling).

I came back a while later and heard the hum but I just chalked it up to sympathetic vibration from the live guitar.
So I turned everything off and went to bed. I turned on the amp this morning and all I get is the hum.

Turning knobs makes no difference except when I turn either the volume or master completely off. Plugging in the guitar makes no difference at any setting.

The amp is less than a few months old (bought new from Sweetwater earlier this year).

Any idea what's going on?
Any help would be greatly appreciated!

 

[tommytubetone]

I looked over a couple of old invoices from when I had mine in the shop over the years. One common thread on both repairs was bad solder joints on the power tube sockets. It could obviously be a thousand things. Regardless, I would contact your Sweetwater rep on Friday and let him know what's going on. They are known for their great customer service. I suspect they will make ir right somehow.

 

[sdbrit68]

yeah, I was gonna go with bad power supply.................................another easy quick check, plug into a different outlet or put a quality power conditioner in front, just to verify not the house electricity

 

[JPsuff]

Ok, this is weird.

Because a room air conditioner has been plugged into the nearest outlet, the amp has been plugged into an extension cord to a different outlet for months.

So I'm looking at the amp and I decide to unplug it from the extension cord and go directly into the outlet the AC has been plugged into.

Now it works fine.

So what the hell was THAT all about?

How could simply changing the outlet fix the problem?

I guess I'll just have to chalk it up to just another crazy aspect of what has to be the craziest year I've ever lived through.

And it's not over yet!

 

[tommytubetone]

It sounds like that extension cord has issues. Try another one and see what happens.

 

[sdbrit68]

multiple reasons besides ground loop..............could be an outlet, too many volts on that particular outlet, electrical interference.

I had a friend waste a ton of money on buzzing and hum, I went over to his house with my Monster cable power conditioner, and monster cables

AS soon as I put the better quality shielded cable on, everything was perfect

electrical impulses (probably bad terminology) can screw with other electrical impulses

 

[CapnDenny1]

Even I can’t fix an amp that ain’t broke. Not that I haven’t tried.

Put it back on the extension cord. If the noise comes back, toss the extension cord.

If it stays quiet, even with the old connection, then it is an intermittent. It may or may not return. I usually have really good luck having the problem return, after I give up trying to get it to fail, and give it back to the customer. I don’t clean jack or pots or tube sockets.

But a new amp should not be having corrosion issues. Hopefully it was the extension cord.

If the noise went away by turning down the volume or the master, then I would suspect the input jack, or the guitar cord.

 

[dvs]

If it's not the cord, take a look at the outlets, too. Are they on the same circuit? If not you may have a problem with a breaker.