Nasty Amp Hum

[Slowy]

I just put a 12ax7 back in the Jansens's V1. Switching on, I'm met with what sounds like a loud earth hum. It's not affected by preamp knobs.
Changed out the valve and it's still there.

The amp was last turned on Tuesday and worked fine.

Advice welcome please!

[jeremyb]

Tried a different guitar and lead? or is this with no guitar plugged in?

[Slowy]

Tried a different guitar and lead? or is this with no guitar plugged in?

Unplugged. Power up and off it goes.

[jeremyb]

Tried a different guitar and lead? or is this with no guitar plugged in?

Unplugged. Power up and off it goes.

Any change with anything plugged in?

[Slowy]

Tried a different guitar and lead? or is this with no guitar plugged in?

Unplugged. Power up and off it goes.

Any change with anything plugged in?

Nope.

[NippleWrestler]

Have you replaced the filter caps on the amp ever? They have a lifespan of 15-20 years with regular use, less than that if the power isn't cycled frequently. When those begin to die hum and flub start to creep in.

[Slowy]

Have you replaced the filter caps on the amp ever? They have a lifespan of 15-20 years with regular use, less than that if the power isn't cycled frequently. When those begin to die hum and flub start to creep in.

I can sense a journey to Clarry's house in my near future.....

[NippleWrestler]

Have you replaced the filter caps on the amp ever? They have a lifespan of 15-20 years with regular use, less than that if the power isn't cycled frequently. When those begin to die hum and flub start to creep in.

I can sense a journey to Clarry's house in my near future.....

If they haven't been changed out it's worth doing anyway as preventative maintenance, especially if they're over 15 yrs old. It's a simple job of changing them yourself too, no need for a tech if you can competently handle a soldering iron and discharge caps (takes about 30 seconds).

[sizzlingbadger]

Try a different set of power tubes, maybe one has gone bad.

[Slowy]

Have you replaced the filter caps on the amp ever? They have a lifespan of 15-20 years with regular use, less than that if the power isn't cycled frequently. When those begin to die hum and flub start to creep in.

I can sense a journey to Clarry's house in my near future.....

If they haven't been changed out it's worth doing anyway as preventative maintenance, especially if they're over 15 yrs old. It's a simple job of changing them yourself too, no need for a tech if you can competently handle a soldering iron and discharge caps (takes about 30 seconds).

I can visualise that and you're right, it's well within my skillset. But Clarry knows this amp, he's maintained it for me and it's time he had another wander through it.

[Slowy]

The only change was in swapping V1 this morning and that's when the hum started. I never got to hear the replacement.
I took out a 12au7 and replaced it with a 12ax7.

The hum is there regardless and it gets to a volume that makes me very concerned for the speaker so mercifully, it's a brief experience.

[murky]

Reflow the solder joints on the tube socket? Check the socket is tight? Might have disturbed something when installing the tube?

[MikeC]

Reflow the solder joints on the tube socket? Check the socket is tight? Might have disturbed something when installing the tube?

So often a change or a fault is due to the last thing that occurred before the change or fault occurred. Even if it seems unrelated.

[Bg]

Reflow the solder joints on the tube socket? Check the socket is tight? Might have disturbed something when installing the tube?

wouldn't hurt to use a bit of contact cleaner in the valve socket too

[NippleWrestler]

The only change was in swapping V1 this morning and that's when the hum started. I never got to hear the replacement.
I took out a 12au7 and replaced it with a 12ax7.

The hum is there regardless and it gets to a volume that makes me very concerned for the speaker so mercifully, it's a brief experience.

So what happens when you put the old tube back in? Could well be a crappy tube.