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Power Tube Popping

TheSeagoats

TheSeagoats

May 21, 2015
530
708
Maryland
#1
I know this is a bass forum but I'm hoping someone here can help me out. I just bought a new 15w guitar amp and after it's turned on it's silent for about 20 seconds, then starts making loud popping noises. This is with the volume all the way down and the cable unplugged. After about a minute of this it stops making the sound and behaves as expected. I've noticed that one of the two power amps flashes blue in time with the popping. Why does is this happening and is there anything I can do to fix it or should I just return it?
 
#2
Needs a new tube is all, I would think. Blue flashes bad. Return for another or get the dealer to simply replace one tube (if they will).
 
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#4
Yes, new tube for sure. Swapping a tube is very easy. Just line the pins up to the holes. There's a spot where a pin should be but isn't. Line that up to the socket and press in firmly. You can pull it out and push in a few times to make sure it has a good connection or clean the tube pins with some deoxit if they are new old stock.

For power tubes I would go with JJs, a matched pair can go for like 24 bucks online. New old stock can go for crazy amounts so I would only do preamp tubes like 12ax7s which you should rarely if ever have to change.

I go through a set of power tubes like once a year or so in an amp with moderate use. Never had to change my preamp tubes.
 
#5
Wait a minute, el84 tubes will commonly make popping sounds as they warm up, mostly mechanical but sometimes the noise may also be electrical as the elements shift. The blue visuals may simply be from the effects of changing electron glow and the surrounding "plasma" field.

Is the amp still under warranty?
 
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#6
agedhorse said:
Wait a minute, el84 tubes will commonly make popping sounds as they warm up, mostly mechanical but sometimes the noise may also be electrical as the elements shift. The blue visuals may simply be from the effects of changing electron glow and the surrounding "plasma" field.

Is the amp still under warranty?
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This is a phone recording I did with my phone last night, does this sound normal to you? There was nothing plugged in while it was doing this. It's my first time with a real tube amp but I don't remember any of my guitarists having issues like this, though they also had standby switches. I also wasn't sure if this was just something like a breaking in period for the tubes or something since the sound disappears after a minute or so. [Invalid or Expired Link Removed]

The amp has a 30 day return policy from the day it was delivered, which was yesterday, so as far as I know I can get a replacement if necessary. I figured if it was a simple fix then I wouldn't go through the hassle. It's a Monoprice 15w tube amp and they sell them dirt cheap so I didn't really expect anything high quality but I did expect it to work.
 
#7
TheSeagoats said:
This is a phone recording I did with my phone last night, does this sound normal to you? There was nothing plugged in while it was doing this. It's my first time with a real tube amp but I don't remember any of my guitarists having issues like this, though they also had standby switches. I also wasn't sure if this was just something like a breaking in period for the tubes or something since the sound disappears after a minute or so. [Invalid or Expired Link Removed]

The amp has a 30 day return policy from the day it was delivered, which was yesterday, so as far as I know I can get a replacement if necessary. I figured if it was a simple fix then I wouldn't go through the hassle. It's a Monoprice 15w tube amp and they sell them dirt cheap so I didn't really expect anything high quality but I did expect it to work.
Click to expand...
yech, that's just nasty... ...don't think that's normal
 
#9
TheSeagoats said:
This is a phone recording I did with my phone last night, does this sound normal to you? There was nothing plugged in while it was doing this. It's my first time with a real tube amp but I don't remember any of my guitarists having issues like this, though they also had standby switches. I also wasn't sure if this was just something like a breaking in period for the tubes or something since the sound disappears after a minute or so. [Invalid or Expired Link Removed]

The amp has a 30 day return policy from the day it was delivered, which was yesterday, so as far as I know I can get a replacement if necessary. I figured if it was a simple fix then I wouldn't go through the hassle. It's a Monoprice 15w tube amp and they sell them dirt cheap so I didn't really expect anything high quality but I did expect it to work.
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I know it may be a hassle, but what if it isn't because of something as simple as a tube?
Get it swapped out for another and see what the next one does.
 
#10
TheSeagoats said:
The amp has a 30 day return policy from the day it was delivered, which was yesterday, so as far as I know I can get a replacement if necessary. I figured if it was a simple fix then I wouldn't go through the hassle. It's a Monoprice 15w tube amp and they sell them dirt cheap so I didn't really expect anything high quality but I did expect it to work.
Click to expand...

Could be a flaky small signal tube. The phase inverter (PI) is normally located after the volume control. So if the PI is noisy, you will hear it even when all controls are at zero. If you have a spare 12AX7, try it in V3. You could also pull V1 and put it in the V3 position if you don't have a spare tube. How does the amp sound after the noise settles down?

Since these amps are so cheap, I would be inclined to ask for a refund or exchange rather than paying for a new tube(s) or repair out of pocket. If you determine only V3 is bad, contact Monoprice to see if they will replace the tube or want you to return the entire amp.
 
#15
TheSeagoats said:
It's in a finished basement but I live in Maryland which tends to be pretty humid. So not really but maybe comparatively speaking?
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I was looking for oppressive humidity and an unairconditioned space.
It was just a thought when you mentioned the changes in the popping.

Are you sure the popping is coming from the tube and not something else?
 
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