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PostPosted: Sat May 12, 2018 9:44 am 
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Mark I

Joined: Sat Jul 30, 2016 1:17 pm
Posts: 24
When I first power on my Mark V, I get some crackling and whooshing. It's still there with input cable removed, so not external source. It's present on all channels, more noticiable as power settings go up from 10->45->90W. Seems to be on all modes, at least in channel 1 - didn't try them all on channel 2 and 3. I usually ignore it and start playing and within a few minutes it's gone and stays gone....maybe 5 min at most. Maybe I just need to warm up powered on in standby longer?

Or should I suspect pre-amp tube failing, and more specifically V1?

Anyone have experience with a similar problem?

I noticed those preamp tubes are a pain to get to without pulling the amp out of the cab...guess I have to move it to a workbench or table where I can get at it a little better :) I haven't had the amp that long and it's only a couple years old, so this is the first time actually really thinking about changing tubes in it...first time I pulled the cage off.


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PostPosted: Sat May 12, 2018 1:07 pm 
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Mark I

Joined: Fri May 06, 2016 10:25 am
Posts: 47
This could be a sign of power tubes starting to show signs of wear. How old are they?


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PostPosted: Mon May 14, 2018 9:56 am 
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Mark III

Joined: Mon Sep 21, 2009 11:03 am
Posts: 235
I always gotten a little buzz noise through the speaker when powering on (in standby). I can recreate the noise when switching power modes on the amp (still on standby).


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PostPosted: Mon May 14, 2018 2:54 pm 
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Bottle Rocket

Joined: Tue Feb 10, 2009 5:30 pm
Posts: 16
This may be too simplistic but but I'll throw it out there: are you taking the amp off standby at the same time as you you flip the power switch on? If so, you may just be hearing the capacitors "spooling up" with power. Leaving the standby switch engaged while powering up will keep that noise from coming through to the speakers. That was something I was doing with a Carr Rambler I have, heard a kind of white noise swell, up and down then it would be gone - I was just getting lazy and throwing both power and standby switches at the same time. Once I did power, wait 20 sec. then standby off, everything stayed quiet.


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PostPosted: Mon May 21, 2018 11:19 am 
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Mark I

Joined: Sat Jul 30, 2016 1:17 pm
Posts: 24
Thanks for the replies.

The power tubes are 2 years old or less. The head is a 2016, not sure what month. And they have not seen very much use. It was shipped across country once, and it has been moved around a few times. So possible a tube got jarred and damaged.

I don't have any noise in standby mode. Just when I turn the amp fully on.

I normally wait about 30 seconds after powering on before coming out of standby.


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PostPosted: Mon May 21, 2018 4:05 pm 
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Mark I

Joined: Fri May 06, 2016 10:25 am
Posts: 47
I play 5 to 10 hrs a week and start getting crackles after about a year. Put in a new set and see if it helps. Even if it doesn’t, you will have a spare set ready to go.


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