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My favorite tube amp started humming. Why?


Barry Wuthrich

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I haven't played my mesa or peavey 10 minutes since I bought a new Laney lionheart L5T 112.

It has all the tone I could ask for and the celestian greenback is awesome. Especially versatile with my mostly boutique pedalboard.

 

I flipped it on a couple of days ago, took it off standby, and it started humming.

I unplugged the guitar and pedalboard to see if it was picking up something outside the amp, and it still was humming.

 

It only has one power tube and one preamp tube, which I drive pretty hard much of the time. About 6 months old.

 

I'm wondering if it's a tube issue, but before I buy new tubes, I thought I'd check with the HC brain trust.

 

Anyone else had this problem? If so, how did you fix it? The amp was dead quiet up till now.

 

Thanks,

Barry

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It's in the same room. I rent a farm house out in the country that has crap for wiring. (2 prong outlets). I have electric heater and fans etc on the circuit, but that was the case before it started humming as well. I cut off the other stuff in the room, and the hum is still there.

 

Black Blade, what do you mean a bad cap? How can I check that?

 

Thanks

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It's in the same room. I rent a farm house out in the country that has crap for wiring. (2 prong outlets). I have electric heater and fans etc on the circuit, but that was the case before it started humming as well. I cut off the other stuff in the room, and the hum is still there.


Black Blade, what do you mean a bad cap? How can I check that?



Thanks

 

 

It sounds like you may have had a capacitor go bad.

They filter the A.C. (60Hz) out.

 

WARNING - Don't mess with Caps unless you know what you are doing!!!

They can hurt you.

 

I recently had a Marshall start humming loud...nothing plugged in...the culprit was a bad cap.

 

Easy fix for a qualified technician.

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It sounds like you may have had a capacitor go bad.

They filter the A.C. (60Hz) out.


WARNING - Don't mess with Caps unless you know what you are doing!!!

They can hurt you.


I recently had a Marshall start humming loud...nothing plugged in...the culprit was a bad cap.


Easy fix for a qualified technician.

And if it's big enough an easy way to lose a finger for an unqualified technician. Heck even a qualified, but hungover technician can get hurt pretty bad.

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I have a buddy with 15w & 30w Laney tube amps. One of each. With bigger tube sets of course. He has his problems too.

 

You've got one power tube and one pre-amp tube and you've been running this "Hot Running" amp, hard for the past 6 months.

I say "Hot Running" because, isn't that what Laney and Vox tube amps are about. Class A

 

This one?

http://www.musicforall.biz/p-333-laney-l5t-112-tube-amp-blues-guitar-harmonica-harp-class-a.aspx

 

The amp was'nt humming and now it is? The cheap fix might be trying a new pre-amp tube. Get the same type for similar tone. I think Hot Running means that the tubes burn bright and hot and I wouldn't expect them to last like in a Fender class AB.

 

Class A amps operate at higher voltages than others amps, which means more heat generated, which can also mean a bit more maintenance and a somewhat shorter lifespan for the tubes involved.

 

Check your tubes from the cheapest one first. Get each. You'll eventually need them anyways.

 

Some tips for fussy VOX and Laney amps from my buddy.

 

Give them time to warm up.

Give them time to cool down before you go and put them away in your cold vehicle after the gig.

Store them up-right so the tubes are standing straight up or hanging down vertically.

This is so that when you go over speed bumps in your vehicle, the tubes aren't bruising side-ways, bending pins/posts and the actual tube's innards. They just can't take the punishment.

And I think, hard working capacitors all die sooner too.

 

This all just goes with the territory of a hot running class A amp.

 

And if you can't fix it yourself,...

 

(Where's the Laney?

It's in the shop!)

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And in a lot of the smaller Class A amps, there's no Bias controls. They say it's self Biasing.

Well, that sounds lame doesn't it?

But, in their design, they weren't expected to last if they were pushed hard?

 

Like a car engine with a nitrous oxide booster. How many led foot stomps can that engine take? 8 maybe?

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Okay. I had a capacitor go out on my water well a couple of times. I changed it myself. I discharged the stored electricity by holding a screwdriver (wooden or rubber handle) across it and grounding it. I think, after that it is safe to handle it as long as you don't plug in the amp and recharge it.

Just to keep it simple, I'll change out the tubes first. I have 8 EL84's in my Mesa Boogies, so I'll just borrow one. If that doesn't work, I'll have someone Ohm the capacitor.

 

Thanks to all,

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It sounds like you may have had a capacitor go bad.

They filter the A.C. (60Hz) out.


WARNING - Don't mess with Caps unless you know what you are doing!!!

They can hurt you.


I recently had a Marshall start humming loud...nothing plugged in...the culprit was a bad cap.


Easy fix for a qualified technician.

 

 

This sounds exactly like a problem I had with my Vox AC15 about a month ago. Switched out the caps and everything was gravy. Suggest you do the same.

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Yes, that's it. I noticed from the spec sheet that it has 3 preamp 12AX7's, so I was wrong in thinking it had only one of each. I'm thinking if it's a tube, it'll be the power tube. That's the one that I drive to breakup. In my Mesa's , you will break your ear drums before the power tubes break up. So all I get is pre-amp distortion, which isn't nearly as warm. The power tube break up on the Laney catches all the voices and harmonics over a wider tonal range. I guess my Mesa probably would too, but I'd be deaf in a couple weeks.

 

Interestingly, the mesa has no bias controls either. They claim that their tubes have a very narrow tolerance, and are therefore closer to specs. This eliminates the need for biasing.

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It's in the same room. I rent a farm house out in the country that has crap for wiring. (2 prong outlets). I have electric heater and fans etc on the circuit, but that was the case before it started humming as well. I cut off the other stuff in the room, and the hum is still there.

 

 

If your signal is buzzing at 60hz, but otherwise unaffected, I'm placing my money on the ungrounded outlets and the {censored}ty wiring. Something else might have gotten plugged into the same circuit, but not the same room.

 

Start by plugging in one of your other amps into the same circuit. Does it buzz? Then it's very likely the circuit. Call an electrician. The place should be brought up to code anyway. In the meantime, don't play barefoot, don't touch anything metal, don't play while wet, etc. You're an accident waiting to happen.

 

If the other amps don't buzz, then perhaps it is a tube or cap in your Laney. Try reseating the tubes first, then replace them (as said, never hurts to have spares). If that doesn't work, I'd be off to the tech with it,

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depending on the type of hum its giving you, it could be a tube too.

tap on the tubes while its humming. see if it changes or goes away.

but yeah as others have said try swapping out tubes before you get into the amp. preamp tubes will do this too.

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How much did it cost?

 

 

Well, I had no clue where any reasonable shops were when I had to take it in, so I had to take it in to some mom and pop place in Atlanta, GA and it ended up being almost $75. Don't know if that's reasonable or not. Never had to do it before or since.

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