Mark IV - what happens if you put the EL-34s on the inside?
- Thread starter Lution
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ANIMATED SUSPENSION
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Don't do it, yes something bad would happen !!! What's the point anyway ?
I'm looking at a used Mark IV combo for sale. The pictures the person sent me clearly show EL34s in the inside slots and 6L6s in the outside slots. Not sure how long it's been running this way.
Just wondering if running the amp this way could damage it? Also, if so, how?
Thanks
Just wondering if running the amp this way could damage it? Also, if so, how?
Thanks
Shep
Well-known member
It can knock out grid resistor's..but if it's still working might be ok..
jerseydrew
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It's not meant to be run that way. Could definitely pose a problem.
Shep said:
He's been using it weekly only running the clean channel. He's going to test out the rest of the channels with the footswitch so I assume it is still working.
Would this cause any wear at all? I'm just trying to foresee some costly repairs due to undue wear or damage on the amp from running it this way.
Also, if there is damage would it be cut and dry - amp don't work - or would it be hard to tell if the amp still supposedly works?
It will mean your EL34's would run a little colder and the 6L6's will run a little hotter.Would only be a problem if the 6L6's ran so hot that they fried.If they are Mesa tubes,they are biased so cold,there isnt much chance they will run too hot.Those EL34's on the inner sockets would run so cold they would likely sound like ****.
LithiumZero
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I saw that amp for sale as well. Hard to say, it could be a great deal or you could get boned. I don't like to gamble. :wink:
I would stay away from it if he's been using it weekly. That's just my opinion though. I would be worried about long term effects on down the road, and I will always have in the back of my mind that the amp was used improperly.
Just my opinion.
Just my opinion.
I'm sort of thinking the same thing here. The Mesa's are biased so cold that you can get away with goof-ups like this without damaging the amp.
Anyways, I got pictures of the guts... real close-up pictures. Everything looks right inside. The owner performed a thorough tone-test cranking the amp and trying all the features and the channels (with the correct tubes in the correct spots, haha) and no problems, no hissing, no noise, no pops, no humming.
So I'm going for it. I will likely take it into Lord Valve to have him check it over when it gets in and have him retube it up.
Thanks for the advice. 8)
Anyways, I got pictures of the guts... real close-up pictures. Everything looks right inside. The owner performed a thorough tone-test cranking the amp and trying all the features and the channels (with the correct tubes in the correct spots, haha) and no problems, no hissing, no noise, no pops, no humming.
So I'm going for it. I will likely take it into Lord Valve to have him check it over when it gets in and have him retube it up.
Thanks for the advice. 8)
In an effort to make you feel better Lution I wanted to chime in. This amp belongs to a good friend of mine.
So you know - I have been working on Tube Amps for over 30 years and I know my way around them. I'm no expert but was Biasing them when I was 10 years old.
First off like everyone said Boogies are Biased Cold so on that fact alone no worries.
#2 Ben's band will not let him play louder than a whisper and I'm not exagerating in the least so his amp isnt working very hard at all.
#3 Boogie has allways put in wayyyyyy over sized Transformers in its Mark Amps and these babys wont go without a fight.
OK now let me go to how he could damage it. Playing it really loud, like dimed for about an hour (he hasnt). With the wrong Bias setting or wrong tubes in the wrong sockets one can fry an amp real quick like that if its dimed and one tube redplates and shorts. Then you get Poof. This hasnt been done with this amp.
There is no I repeat no such thing as it having some damage and still working. If it works for him now it works.
Lution I think your getting this amp at a pretty decent price and once its tweaked and working properly it should do you a great service.
I would recomend you take it straight out of the UPS box and straight to a Mesa Qualified Tech. I would ask it be checked from one end to the other. I would make sure it has good tubes in it and the Bias is properly set.
Good Luck with your new amp!
So you know - I have been working on Tube Amps for over 30 years and I know my way around them. I'm no expert but was Biasing them when I was 10 years old.
First off like everyone said Boogies are Biased Cold so on that fact alone no worries.
#2 Ben's band will not let him play louder than a whisper and I'm not exagerating in the least so his amp isnt working very hard at all.
#3 Boogie has allways put in wayyyyyy over sized Transformers in its Mark Amps and these babys wont go without a fight.
OK now let me go to how he could damage it. Playing it really loud, like dimed for about an hour (he hasnt). With the wrong Bias setting or wrong tubes in the wrong sockets one can fry an amp real quick like that if its dimed and one tube redplates and shorts. Then you get Poof. This hasnt been done with this amp.
There is no I repeat no such thing as it having some damage and still working. If it works for him now it works.
Lution I think your getting this amp at a pretty decent price and once its tweaked and working properly it should do you a great service.
I would recomend you take it straight out of the UPS box and straight to a Mesa Qualified Tech. I would ask it be checked from one end to the other. I would make sure it has good tubes in it and the Bias is properly set.
Good Luck with your new amp!
Boogiebabies
Well-known member
It's heat, high natural plate current or a screen failure that makes the grid resistor either brown or blow up. Even if the bias is as you say "Cold", there is always a chance that you will stick a tube in there that will naturally draw a bias that could be 90+% of max plate dissipation. Different tube types react differently to the same plate voltage and bias so while the screen grid is being used to control plate dissipation, if it's running 90-100%, it's going to take a beating and eventually give up due to heat. Any internal shorts can pose the possibility that they will simply blow up from over voltage.
The old lightning in a bottle or red plating can just wear the resistor out until it blows. I caught an amp red plating and in the course of 30 seconds or so, it lowered the resistance of a 470 Ohm screen grid to 200 Ohms. I'm sure it was just before the resistor was going to go or the fuse was going to pop. In retrospect, Mesa moved away from the vintage style 470 Ohm resistors. On some MK III's they used a diode and later at least a larger 2.7K resistor. On the IV, some early ones have the vintage style 2.7K and then they finally used a ceramic flame proof 2.7K. These both seem to handle EL-34's quite well and rarely fail. The old style would catch on fire and made quite a stink.
If you wanted to run EL-34's in your amp, it's not too much of a problem to upgrade the inner sockets screen grid resistors to at least 1K 2W to be safe. That's what Mesa has been running in the Rectifiers and they handle EL-34's and 6L6's just fine.
The old lightning in a bottle or red plating can just wear the resistor out until it blows. I caught an amp red plating and in the course of 30 seconds or so, it lowered the resistance of a 470 Ohm screen grid to 200 Ohms. I'm sure it was just before the resistor was going to go or the fuse was going to pop. In retrospect, Mesa moved away from the vintage style 470 Ohm resistors. On some MK III's they used a diode and later at least a larger 2.7K resistor. On the IV, some early ones have the vintage style 2.7K and then they finally used a ceramic flame proof 2.7K. These both seem to handle EL-34's quite well and rarely fail. The old style would catch on fire and made quite a stink.
If you wanted to run EL-34's in your amp, it's not too much of a problem to upgrade the inner sockets screen grid resistors to at least 1K 2W to be safe. That's what Mesa has been running in the Rectifiers and they handle EL-34's and 6L6's just fine.
