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Nasty Amp Hum
Posted: Sun Aug 13, 2023 12:43 pm
by 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!
Re: Nasty Amp Hum
Posted: Sun Aug 13, 2023 12:45 pm
by jeremyb
Tried a different guitar and lead? or is this with no guitar plugged in?
Re: Nasty Amp Hum
Posted: Sun Aug 13, 2023 12:46 pm
by Slowy
jeremyb wrote: ↑Sun Aug 13, 2023 12:45 pm
Tried a different guitar and lead? or is this with no guitar plugged in?
Unplugged. Power up and off it goes.
Re: Nasty Amp Hum
Posted: Sun Aug 13, 2023 1:43 pm
by jeremyb
Slowy wrote: ↑Sun Aug 13, 2023 12:46 pm
jeremyb wrote: ↑Sun Aug 13, 2023 12:45 pm
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?
Re: Nasty Amp Hum
Posted: Sun Aug 13, 2023 1:52 pm
by Slowy
jeremyb wrote: ↑Sun Aug 13, 2023 1:43 pm
Slowy wrote: ↑Sun Aug 13, 2023 12:46 pm
jeremyb wrote: ↑Sun Aug 13, 2023 12:45 pm
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.
Re: Nasty Amp Hum
Posted: Sun Aug 13, 2023 2:08 pm
by 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.
Re: Nasty Amp Hum
Posted: Sun Aug 13, 2023 2:10 pm
by Slowy
NippleWrestler wrote: ↑Sun Aug 13, 2023 2:08 pm
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.....
Re: Nasty Amp Hum
Posted: Sun Aug 13, 2023 2:34 pm
by NippleWrestler
Slowy wrote: ↑Sun Aug 13, 2023 2:10 pm
NippleWrestler wrote: ↑Sun Aug 13, 2023 2:08 pm
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).
Re: Nasty Amp Hum
Posted: Sun Aug 13, 2023 2:34 pm
by sizzlingbadger
Try a different set of power tubes, maybe one has gone bad.
Re: Nasty Amp Hum
Posted: Sun Aug 13, 2023 2:56 pm
by Slowy
NippleWrestler wrote: ↑Sun Aug 13, 2023 2:34 pm
Slowy wrote: ↑Sun Aug 13, 2023 2:10 pm
NippleWrestler wrote: ↑Sun Aug 13, 2023 2:08 pm
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.
Re: Nasty Amp Hum
Posted: Sun Aug 13, 2023 3:03 pm
by 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.
Re: Nasty Amp Hum
Posted: Mon Aug 14, 2023 8:29 am
by murky
Reflow the solder joints on the tube socket? Check the socket is tight? Might have disturbed something when installing the tube?
Re: Nasty Amp Hum
Posted: Mon Aug 14, 2023 8:32 am
by MikeC
murky wrote: ↑Mon Aug 14, 2023 8:29 am
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.
Re: Nasty Amp Hum
Posted: Mon Aug 14, 2023 9:23 am
by Bg
murky wrote: ↑Mon Aug 14, 2023 8:29 am
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
Re: Nasty Amp Hum
Posted: Mon Aug 14, 2023 10:11 am
by NippleWrestler
Slowy wrote: ↑Sun Aug 13, 2023 3:03 pm
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.