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PostPosted: Sat Jul 17, 2010 3:10 pm 
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Joined: Tue May 10, 2005 3:39 am
Posts: 2504
Location: Birmingham, AL
chateauneuf wrote:
Any amp with 84s is going to have that problem. Espcially a $450 Chinese vox...if you want more reliable 84s, you can spend more money on NOS tubes, but EL84s are designed to be pushed hard and as a result they have always been the shortest lived of the guitar amp power tubes.

If you're gigging a $1000 amp, you ought to have a $25 pair of tubes and a fuse for a backup anyway.

Thanks. Money for the tubes wasn't really an issue. I've already gone through 3 pairs in less than 2 months. I've got to admit this is my first amp using 84s. I got this amp because of the size convenience, I've got a Mark V for any 'bigger' gigs. But popping in new tubes in-between sets doesn't strike me as being convenient. I'll see if I can find any NOS around here and see if that remedies the problem. Does Mesa make them (for warranty reasons)? Thanks for your advice, I'll give it a try.


Popping a new set of tubes in between sets seems more convenient to me than shuttin down a gig ;)

NOS means New Old Stock. Mesa doesn't make any tubes, but of the tubes they do currently sell, only the STR 450 EL34 is an NOS tube.

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PostPosted: Sat Jul 17, 2010 8:19 pm 
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Bottle Rocket

Joined: Thu Jun 24, 2010 12:30 pm
Posts: 7
I've had the same problem with my transatlantic as well. So far in my reading the solutions are to swap in new Ax7 or replacing the power tubes. If I call Mesa will these fall under warranty? Also what is the general life span of the EL84? I rehearse with my band everyday for about 2 hours. What is a suitable power tube replacement? forgive my tube ignorance but what are JJ tubes and their price? Still I haven't loved a lunch box this much since my star trek 4 lunch box I got from universal studios when I was 6. (looks up reflectively) I loved that freakin Lunch Box : )


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PostPosted: Sun Aug 01, 2010 8:40 am 
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Bottle Rocket

Joined: Sun Aug 30, 2009 7:50 am
Posts: 6
Location: USA
I have the same trouble after one week with this amp.
I will call mesa for replacement tubes this week.

Can I put JJ EL84's or 12ax7's until I receive the mesa ones?
Will it damage to amp? Does it void the warranty?

If you had the same problem and replaced tubes did
it happen again? Any real problem with the amp?

Thanks.


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PostPosted: Mon Aug 02, 2010 2:02 pm 
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Mark I

Joined: Sun Oct 19, 2008 4:48 pm
Posts: 49
Location: England
kbaird wrote:
I have the same trouble after one week with this amp.
I will call mesa for replacement tubes this week.

Can I put JJ EL84's or 12ax7's until I receive the mesa ones?
Will it damage to amp? Does it void the warranty?

If you had the same problem and replaced tubes did
it happen again? Any real problem with the amp?

Thanks.


I've had the TA for about 2 weeks now and 'fingers crossed' I've not had any problems with the tubes. But this thread is starting to worry me! Is it possible that modern EL84s are so unreliable? My only other experiennce of an EL84 amp is the Peavey Classic 30 which I ran with the same tubes for over 10 years! When I eventually did change them Iused JJs with no problems.

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PostPosted: Tue Aug 03, 2010 3:33 pm 
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Bottle Rocket

Joined: Tue Jul 13, 2010 7:29 pm
Posts: 4
Rich at Mesa Boogie was kind enough to send me a new set of EL84s and one 12AX7 to put in the V1 slot.
So far so good, I've used it for two weeks now and it hasn't cut out on me yet (touch wood). This would be my
third set of EL84s, so it MIGHT have been the 12AX7 in the V1 slot, I'm not sure since I put the
new EL84s and 12AX7 in at the same time. But I don't care, as long as it works, I'm happy.
I'll keep you posted if I have any more troubles.


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PostPosted: Sun Dec 04, 2016 4:49 pm 
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Bottle Rocket

Joined: Sun Dec 04, 2016 4:34 pm
Posts: 2
I have a Ta-15 with this problem, the volume drops after some time playing. It happens on the two channels. If I put it in standby mode and turn it on again the problem goes away, but if I continue playing, the problem happens again.

I've changed all the preamp and power tubes, but the problem continues. Does anyone know what can be happening?

Thanks.


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PostPosted: Thu Apr 06, 2017 6:45 am 
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Bottle Rocket

Joined: Sun Dec 04, 2016 4:34 pm
Posts: 2
Well, this is an update to my previous post.

I've noticed that the problem only happens in Class AB mode, 25W. I think it can be a BIAS problem. I have two sets of Mesa Boggie el84 tubes.

The one I bought new to put in the TA-15 causes this problem in 25w mode, but if I put them in a Mini Rectifier which I also own, It works perfectly. These are grey coded.

If I take the tube set that came with the Mini Rectifier (grey code too), and put them into the TA 15, it works well.

So it seems that it is very sensible to the tube set you put in it.


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