Reply to this topicStart new topic
> Amp Smoking, Then Crackling... Not Cool!
Zephyr
post Oct 18 2008, 01:38 AM
Post #1


GMC:er
*

Group: Members
Posts: 535
Joined: 23-August 07
Member No.: 2.595



So, let's see if I can explain this in a way that makes sense to anyone. Okay, first of all, I have a Mesa Boogie Mark III. It's got four power tubes, with a switch from Class A (outer 2 tubes on, 60 watts) to Simul-Class (all four, 100 watts). It had JJ 6L6's in the middle (simul-class) spots, and Mesa El-34's (ancient tubes, the originals the amp came with in 1987!) in the outer 2.

I recently got a new set of Tung-Sol preamp tubes and two Mullard EL-34's from my guitar teacher. I put them in, (the EL-34's replacing the Mesa ones, 6L6's still the JJ's). and it instantly sounded better than it ever has before. Pretty neat. He also gave me two Ruby 6L6's that another student had switched out; I guess just a preference thing; free of charge. One of them was missing the 'guiding pin,' the black bit with the notch in the middle. He assured me that it would still work fine without it, I've read that online as well. Sweet.

So I switched the EL-34's for the Ruby's, turned the amp on, let the tubes warm, switched off standby, and about 5 seconds it, the amp started crackling horribly and smoking. I switched it off and unplugged it as fast as I could. Now, the amp should work fine with 6L6's in all four positions, at least from everything I've read about it. Both tubes were in the right way, I checked the one without the guide against the one that had it.

After I let it cool down for a long time, I switched the Ruby's back out for the Mullard's, and turned it on. It worked fine, no smoke or anything, but when I played hard enough for it to clip, there was a very bad sounding crackling noise. It was much more noticeable in the Class A mode than the Simul-Class. My guess is, one of the tubes was somehow bad, and screwed up the slot it was in. I've decided to leave it off until I find out what's wrong.

Anyone have any ideas what happened or what to do? Thank you!
Go to the top of the page
 
+Quote Post
bladzerok
post Oct 18 2008, 02:18 AM
Post #2


Learning Guitar Hero
*

Group: Members
Posts: 355
Joined: 25-January 08
Member No.: 3.977



wow... thats weird blink.gif
i think you should bring your amp to a tech, making sur not to completely break your amp by trying to repair it alone. plus it sounds like a cool amp.

btw you should have freaked out when your amp smoked, uh?

sorry if im not being really helpful, im new to tube amps, but there is one thing that im sure: you should get it examinated by a professionnal.

good luck with that mate


--------------------
My gears are:
guitars:
-simon and patrick accoustic guitar
-ovation accoustic guitar
-Ibanez S320 electric guitar
-Ibanez RG7321 electric guitar
amp:
-Peavey valveking 112
effects:
-Boss SD-1
-Dunlop crybaby from hell
-Boss GE-7 7-Band Equaliser
-Boss NS-2 Noise Supressor
Go to the top of the page
 
+Quote Post
Zephyr
post Oct 18 2008, 03:13 AM
Post #3


GMC:er
*

Group: Members
Posts: 535
Joined: 23-August 07
Member No.: 2.595



P.S. I just got a response from my teacher, he says that 6L6's shouldn't be used in the outer 2 slots unless you have a mod done to it. He said to check the fuse (which is fine) and the preamp tubes, one might have fried when the tube freaked out. I guess I'll do that, let me know if someone has another idea!
Go to the top of the page
 
+Quote Post
Fullmetal_Tmd
post Oct 18 2008, 03:40 AM
Post #4


GMC:er
*

Group: Members
Posts: 173
Joined: 26-April 08
From: Kansas :/
Member No.: 4.986



I heard somewhere that when you switch tubes, you have to do something called "Biasing" the new tubes to work properly. Thats probably what you're teacher was talking about, if I'm not mistaken. I'm not sure on the process, because I don't have a tube amp (just a hybrid), so I can't help you there.

Good luck getting your Mesa back into working condition, it'd be a shame to lose such a valuable gem =/


--------------------
Go to the top of the page
 
+Quote Post
timmy
post Oct 18 2008, 04:30 AM
Post #5


GMC:er
*

Group: Members
Posts: 5
Joined: 2-October 08
From: South Carolina
Member No.: 6.016



blink.gif
Guys....biasing is setting the optimum operating voltage for a tube type that is designed to be used in an amp or amp section. I am not a Mesa Expert but in general the voltages between 6L6 tube and EL34s are different. Using the wrong power tube can damage your transformer. The rule of thumb is

6L6 in an EL34 = yes
EL34 in a 6L6 = no

A mod to be able to run this, is to change the resistance in the circuit it's self, and then you can run both tube types, but they must be biased to operate properly because of the difference in voltage between the tube types. This should not be done by a non-technical person.

Checking the preamp tubes is a good idea and also try replacing the the 6L6 tubes that were in the correct slots when you made the switch. They may have suffered some damage. If tube swapping does not work then take it to a tech!
Tube amps pack lots of voltage, even when they are turned off and unplugged. They store electricity and if you cross the right conections, it can deliver enough energy to kill you. Leave this to an amp tech.
Go to the top of the page
 
+Quote Post
MickeM
post Oct 18 2008, 10:48 AM
Post #6


Born of NWOBHM, Moderation Team Leader
*

Group: Members
Posts: 8.562
Joined: 9-January 07
From: Stockholm, Sweden
Member No.: 1.062



Maybe a bias issue to start with. Since you replaced EL34's with 6L6's which require a different bias. You said it happened when you put it to standby and sure, the amp lets current through in stanby but that's less that when it on. So I don't know what could have fried though.
And I don't know about the bias current but like timmy describes it it seem like EL34's has a lower bias current.

The cackling you hear is typical for a tube gone bad. Check if any is luminated oddly or sings when you pat it with a pen.
And btw when changing tubes one should also add some electric spray to clean the sockets up bit.

EDIT: I's suggest you have a tech take a look at it.

This post has been edited by MickeM: Oct 18 2008, 10:49 AM


--------------------
Go to the top of the page
 
+Quote Post
Ian Bushell
post Oct 18 2008, 11:09 AM
Post #7


Instructor
Group Icon

Group: GMC Instructor
Posts: 956
Joined: 21-June 08
From: Johannesburg, South Africa
Member No.: 5.345



QUOTE (timmy @ Oct 18 2008, 05:30 AM) *
blink.gif
Guys....biasing is setting the optimum operating voltage for a tube type that is designed to be used in an amp or amp section. I am not a Mesa Expert but in general the voltages between 6L6 tube and EL34s are different. Using the wrong power tube can damage your transformer. The rule of thumb is

6L6 in an EL34 = yes
EL34 in a 6L6 = no

A mod to be able to run this, is to change the resistance in the circuit it's self, and then you can run both tube types, but they must be biased to operate properly because of the difference in voltage between the tube types. This should not be done by a non-technical person.

Checking the preamp tubes is a good idea and also try replacing the the 6L6 tubes that were in the correct slots when you made the switch. They may have suffered some damage. If tube swapping does not work then take it to a tech!
Tube amps pack lots of voltage, even when they are turned off and unplugged. They store electricity and if you cross the right conections, it can deliver enough energy to kill you. Leave this to an amp tech.

To my knowledge of tube amps this sounds right. You have to be really careful with the type of valves you put in your head.
Definately agree take it in to an amp tech to check out.
Just out of interest where the smoke is concerned you didn't spill something on the amp while it was on?


--------------------
I use D'addario and Planet Waves
Video Lessons
Myspace
Go to the top of the page
 
+Quote Post
Muris Varajic
post Oct 18 2008, 11:39 AM
Post #8


Instructor
Group Icon

Group: GMC Instructor
Posts: 15.459
Joined: 22-June 07
From: Sarajevo,Bosnia
Member No.: 2.159



I never had similar problems
tho I never experimented a lot with tubes either.
I guess bias is the issue,take it to the tech to be sure. smile.gif


--------------------
Youtube
MySpace
Website



Album "Let It Out" on
iTunes
and CD Baby

Check out my video lessons and instructor board!

The Pianist
tune is progress,check it out!

"ok.. it is great.. :P

have you myspace? Can i to personalize this for you guy?"
Go to the top of the page
 
+Quote Post
Zephyr
post Oct 21 2008, 05:28 AM
Post #9


GMC:er
*

Group: Members
Posts: 535
Joined: 23-August 07
Member No.: 2.595



Hey, sorry for never getting back to anyone. Thanks for the advice, but the problem is somewhat solved. Long story short, it turns out that one of the power tubes was bad anyways, all the other tubes are fine, and you can use 6L6s in the outer slots.

The only problem is the crackling in the Class A mode is still there, not sure what it is. All the preamp tubes are fine, tested them one by one. Electrical problem, maybe? Do you think it's safe to run it? The crackling isn't there in the Simul-Class mode, which I always use anyways.

Anyways, thanks guys!

P.S. I've heard that Mesa amps don't need to be biased, at least the Mark series. Is this not true?

This post has been edited by Zephyr: Oct 21 2008, 05:29 AM
Go to the top of the page
 
+Quote Post
MickeM
post Oct 21 2008, 07:19 AM
Post #10


Born of NWOBHM, Moderation Team Leader
*

Group: Members
Posts: 8.562
Joined: 9-January 07
From: Stockholm, Sweden
Member No.: 1.062



QUOTE (Zephyr @ Oct 21 2008, 06:28 AM) *
Hey, sorry for never getting back to anyone. Thanks for the advice, but the problem is somewhat solved. Long story short, it turns out that one of the power tubes was bad anyways, all the other tubes are fine, and you can use 6L6s in the outer slots.

The only problem is the crackling in the Class A mode is still there, not sure what it is. All the preamp tubes are fine, tested them one by one. Electrical problem, maybe? Do you think it's safe to run it? The crackling isn't there in the Simul-Class mode, which I always use anyways.

Anyways, thanks guys!

P.S. I've heard that Mesa amps don't need to be biased, at least the Mark series. Is this not true?

But still, I never had a poweramp go up in smoke before so I don't think that's right. I'm still suggesting you leave it for service.
There are self biasing amps and the manual should say if yours is or isn't.


--------------------
Go to the top of the page
 
+Quote Post
Ivan Milenkovic
post Oct 21 2008, 12:26 PM
Post #11


Instructor
Group Icon

Group: GMC Instructor
Posts: 25.396
Joined: 20-November 07
From: Belgrade, Serbia
Member No.: 3.341



I agree with everyone here, if you have crackling in Class A mode, it is best to go and check it out now, then later mate.


--------------------
- Ivan's Video Chat Lesson Notes HERE
- Check out my GMC Profile and Lessons
- (Please subscribe to my) YouTube Official Channel
- Let's be connected through ! Facebook! :)
Go to the top of the page
 
+Quote Post
OrganisedConfusi...
post Oct 21 2008, 01:17 PM
Post #12


GMC:er
*

Group: Members
Posts: 5.635
Joined: 29-November 07
From: Nottingham, UK
Member No.: 3.401



QUOTE (MickeM @ Oct 21 2008, 07:19 AM) *
But still, I never had a poweramp go up in smoke before so I don't think that's right. I'm still suggesting you leave it for service.
There are self biasing amps and the manual should say if yours is or isn't.

I'm pretty sure that the MESA amp he has is a self biasing amp but it will say in the manual if you check it out.


--------------------
Gear
Guitars:- Caparison Horus Snowcloud, Parker Nitefly M, Parker Nitefly SA, Gibson SG, Parker P10e, 40 Year Old Spanish Acoustic
Amps:- Framus Ruby Riot 2x12" stack
Go to the top of the page
 
+Quote Post

Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

 


RSS Lo-Fi Version Time is now: 22nd January 2017 - 12:39 AM