# tube amp sounding very bad



## Rick31797 (Apr 20, 2007)

i suspect there is a bad tube maybe more then one, but they all light up, can a tube still be bad, i have no tube tester, would i just replace one at a time and try the amp each, time to eliminate the bad one, there are 6 tubes,


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## StevieMac (Mar 4, 2006)

Suggestion: you really need to be more specific, especially about what "sounding very bad" means, sonically speaking. Crackles? Noise/Hiss? Ringing/Microphonic sounds? This will help narrow down the usual suspects.

Briefly, a tube can definitely "light up" and still have serious functional issues. Assuming you're talking preamp tubes only, wiggle each of them, one at a time, when the amp is on and volume is up some. One of them may stand out as being obviously noisy when wiggled. Be aware, that could also be caused by a poor/dirty connection between the tube and socket however. You can also tap on each of them with a pencil when the volume is up, to check for microphonic tubes. 

I'm sure others can chime in here...

Steve


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## Rick31797 (Apr 20, 2007)

well is far as the sound, it sounds like a very bad distortion pedal., or blown speaker, i did change the small tubes one at a time with no luck, there are two big tubes , but i dont have any at the moment so will try them when i get one.


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## keto (May 23, 2006)

wear gloves if you wiggle them when amp is on. Them suckers is hot.

You know that there is a big difference between power tubes and preamp tubes? The preamps being most commonly 12AX7's (you didnt say what type of amp you have), smaller than the power tubes. Generally speaking, they are more prone to failure than power tubes, which (again, generalizing) get weaker over time on a very long and gradual slope but don't nearly as often just crash on you.


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## StevieMac (Mar 4, 2006)

Are you sure it's not your speaker? If possible, plug into another cab to check.

If you want to rule out a bad preamp tube however, you can substitute a new or known-to-be-good preamp tube in each slot, one at a time, and see if the distortion goes away when one particular tube has been substituted.


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## Rick31797 (Apr 20, 2007)

the amp is a mesa ta-15 so it has 4 -12AX7 and 2-EL 84.. I tried another amp with the speaker cabinet and it sounded fine.


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## keto (May 23, 2006)

Yeah, do you have spare tubes around?

EL84's have (again, so many generalizations) the shortest lifespan of the common power tubes, so it could be one or both of them. Most Mesa's are self biasing, so if you have a spare you should be able to just pop it right in there with no issues, replace each in turn to test. And, as Stevie suggested, if you have a spare 12AX7 around, try putting it in each preamp slot in turn to see if you can eliminate a bad one. If you use a known good tube to do this and don't eliminate the problem, you may have deeper problems in need of a tech's eyes and tools.


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## Rick31797 (Apr 20, 2007)

i went to the mesa site and went through the steps to check the tubes they told me to take all the tubes out and check fuse , and then turn on amp..if it shuts down, then there is a more serious problem, mine stayed on. and i checked each tube and i have it narrowed down too one EL -84 TUBE.. IT has a couple small rectangular holes and i can see a purple glow,and some discolouration around the hole, from heat.. the other tube has the same rectangular holes but does not glow....... so it looks like i need to buy a matched set . any thought on a make to try, instead of replacing with mesa.


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## StevieMac (Mar 4, 2006)

I have a matched quad of JJs if you need some. They're actually "used" but were only in the amp for a month or two. Anyway, I'm around Kingston and you'd be welcome to them.


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## Rick31797 (Apr 20, 2007)

I am near Napanee, should be coming to Kingston within a week or so,Thanks for the offer, will let you know.


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## keto (May 23, 2006)

Yeah, JJ's for current production EL84's pretty much have the best overall reputation.


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## StevieMac (Mar 4, 2006)

Agreed, and considering these ones are offered up for free, you also can't beat the price. *;^)*


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## Rick31797 (Apr 20, 2007)

> Agreed, and considering these ones are offered up for free, you also can't beat the price.


Santa just keeps on giving..lol


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## Wild Bill (May 3, 2006)

Just a caution! Tubes are indeed the most common suspects but there are LOTS of resistors, capacitors and stuff inside the amp that can also fail. Checking tubes is always the first step but you may need a tech. The Mesa advice about taking out all the tubes and trying the amp is only a VERY general test! It's like running your car while it's parked. It can sound great but if you take it out on the street a wheel could still fall off!

Tubes are wearable devices. They gradually wear out. Preamp tubes are voltage amplifiers. They can go screwy like anything else but other than that they usually last for years and years. I have pulled them out of old equipment when they are 50 years old and most of the time they still work! Modern tubes are not made to the same quality level but still, they give great life!

Power tubes deal with big gobs of current. If the amp is played a lot you can expect a few years of life, maybe a bit more.

If certain parts fail a tube might be stressed and burn out quickly. You can replace the tube but if it failed from such a situation you will lose the new one soon too! When you replace output tubes, look through the glass at the dark outside shell - that's called the plate. If something is wrong in the circuit you will probably see an orange or red "hot spot" on the plate. This is bad, VERY bad! You need to then get your amp to a tech.

If there are no signs of hot spots after replacing the output tubes and the amp sounds fine, then crank her up to 11 and wail!:rockon:

Wild Bill/Busen Amps


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## Rick31797 (Apr 20, 2007)

The amp was used when i got it not sure how much it was used before that, but i dont use it much at all.. i see one tube really glows red down the tube , also when i turn it on and let it warm up, and flipped the standby switch on,.... there was a spark at the bottom of the tube, and then it started to glow red down the side.....the other tube looks fine., here a picture...


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## Wild Bill (May 3, 2006)

That tube is definitely snackered! The question is, did the tube just fail or did something else MAKE it fail?

You will have to replace the tube anyway and best replace both with a matched pair. Tubes are tough so they likely won't be harmed if you turn on the amp and watch to see if the new tube makes the same overheating spots. I wouldn't play the amp for hours with such a problem but if you simply watch to make sure that the problem is gone and turn things off if the problem starts up with the new tube you should be fine.

If the new tube still shows the same problem make sure that you note which position it's in. That sort of thing makes it easier for the tech!


Wild Bill/Busen Amps


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## Rick31797 (Apr 20, 2007)

Just an update on this Mesa TA-15, i did change the tubes and it worked for 5 mins then it started to get really distorted and make crackling sounds, much more going on, the good news is this amp is suppose to be still under warranty, the bad news is, it looks like it will either have to go to Kitchener ,London, or Sebright were ever that is.Wish Mesa had more repair centres then 3 in Ontario, going to have to pay for shipping there and back.


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## nonreverb (Sep 19, 2006)

I'm a mesa warranty depot if you want to drive to Ottawa...


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## Rick31797 (Apr 20, 2007)

i may consider this as we have family in Ottawa..i wonder why they dont list you on there web site, there is only 3 listed


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## nonreverb (Sep 19, 2006)

I don't know, I'm the best kept secret...considering I've been one for about 4 years and have excellent references....
Either way, I'm off the 416 in Bell's Corners which would make it easy for you.


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## Rick31797 (Apr 20, 2007)

Thanks for contacting me, if i don't make it there, my brother-in law, should be coming here in the near future, i will just send the amp with him, he doesn't live very far from you and could drop it off..


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## nonreverb (Sep 19, 2006)

No problem. Just make sure you have your proof of purchase and you're good to go!


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