Mark V 25 Problem

Hello!

I have a Mark V 25 that sounds very good, but now I have some problems with the amp.
It's so that after I have turn the power on (stand by mode) and after a couple of minutes I turn the stand by on and start to play.

After a while the volume drops and stays like this for some seconds and then the volume comes back.
This happens also when I go from channel 1 to channel 2.

I allways have the cabinet pluged in, if I don't used it, I switch it off by the switch on the rear panel.

So my question is, could the preamp or power tubes or both gone bad?

As the issue is in both channels the common is the power section but I think the Mark series do use some common tubes in the circuit for both channels. I had a preamp tube that was or went bad right out of the box (actually a Mesa set of tubes) it's electronics, it happens. When troubleshooting always do one thing at a time. Check the power tubes see if one is brighter that the other. You may be able to see a difference. If there is a difference, shut it down, unplug the amp, safety first! Try reseating that tube. If no change continue with all the tubes, one at a time. Repeat. Always unplug the amp, one hand at a time when reaching into the amp. Allow no direct path through your heart the capacitors in there are charged even when the amp is unplugged. If no change take it to Mesa for repair. I don't know where you are but the Mesa Hollywood guys are the best around.

Tidbit: when dealing with a bad tube but you cannot tell which tube is bad, replace one tube at a time. If no change put the old tube back in and replace the another. If your problem is fixed you have identified the bad tube. I always put tubes in as sets and keep the old tubes as spares but that is me. I actually have a tube tester so I spec them and keep the ones that test good. A tube tester is not necessary I usually test tubes when I am bored and have not specced a few that were replaced. Tubes usually don't but they can at anytime fail. Get a spare set.

At jobs I take a spare amp as it is much faster to switch amps than to try and troubleshoot on the job.

Was that me bloviating? Never, not me, can't happen.

Very possible a preamp tube (generally a 12ax7 type), or even the driver tube (also a 12ax7) for the output tubes.
As it's a new amp, it still is under warranty (even if you happened to buy it second hand...warranty is transferable) and Mesa has great service.

Give them a call and they will help you figure it out.
If they believe it is a tube issue, they will usually just send you a new one, no charge.

More than likely, that will fix it!

Good luck! :wink:

Thank you for the replies.

I have already sent a mail to Mesa Boogie and described the issue.

I think also that it could be 1 or more of the tubes that has gone bad, I has to wait and see what they are saying, before I do anything.

Oh it's a long way to Mesa Hoolywood, since I live in Sweden.

I have to use my Kemper Amp as long I am waiting, I have profiled the Mark V 25, it sounds as close as it can, but not as the real thing.

Sweden... That would be a little bit of a ways away.

But good luck. I am sure you will get it up and running.

Please keep us posted on the solution.

It is helpful for when people with similar issues search through these threads in the future when they can see what the final solution was.

Change all the tubes. You can rule out a tube problems and then you'll have a spare set, which you really need anyway. I believe Mesa will reimburse you if you find a bad one.

If the problem persists then you will know for sure that you have to send it to a tech.

Thank you all for ideas and thoghts.
I have sent a mail to Mesa Boogie about the problems I have with the amp.
I am waiting for spare tubes I have ordered and see if I can find if it's the tubes.

The problem don't comes right away, after a while when I have played the amp, then the volume drops and comes back after approx 1-2 sec, so I am sure that the problem could be one or more of tubes.

I will inform you all how the progress goes with the amp.

Thank you all.

One more thing you can try, assuming you have no spare tubes at all.....
Rotate all the 12ax7 preamp tubes down one position; move tube from the first socket to the second, second one to the third and so on.
Since different stages of the amp work under different parameters (plate voltage, amount of gain, cathode follower configuration or not, etc.) a tube that acts up in one position may work fine in another. If it starts working better than you are on the right track.

This procedure will at least tell you if it is a tube (though it may not immediately tell you which one).
At least you will know it is not a more serious problem in the amp.
Of course if you can find a spare good tube, swapping one at a time, as suggested earlier, would be the best way to know for sure.
Good luck!

Hello Everybody!

I have solved the problem with my Mark V 25 now.
I shifted around all the preamp tubes in different positions, but different other problems came.
Sometimes the reverb didn't work, sometimes the distortion where lower than it should.
After this I changed all the tubes, even the power tubes and then my amp was working again.

I sent a mail to Mesa Boogie and he suggested that I should do as I did and he also said that if this happen, the could be one or more of the tubes. It can also be that one relay inside the amp has gone bad.

So now I happy again

Thank you all for the feedback.

Excellent!

Thanks for letting us know what it was.

Yeah, the moment the problem started to move when you moved the tubes around was a clear indication. Well, that and when you replaced them the problem went away

Hey guys, quick question: In the last rehearsal whenever I tried to run the gain at 4'o clock, treble at 2 o'clock, mids at 11 o'clock,bass at 10 o'clock, presence at 2 o'clock and the master at 12 o'clock, plus graphic eq with a V, but without completly cutting the mids, If I pushed the presence or the master volume any further (just for the sake of testing to see how much louder it would get, it was already loud enough to keep up with the drummer with the master at 11 o'clock), the amp would start to give a high pitched noise but not like feedback. I read in the manual that pushing to much presence could cause something like that, but can you guys confirm it? Or is it some other issue?This happened even with the guitar muted. Since I've seen some mesa boogie mark v postd talking of a high pitched squeal I wanted to know if it is normal.

Besta regards,
Ricardo

Hello Sawyer!

That sounds no good. May I ask why do you have both gain and presence that high?

I have my gain between 11:00-12:00, master at 10:00 and presence about 10:00-10:30 on channel 2 and it sounds very good.

I think you could have problems with your power tubes, they became microphonic so they amplify the vibrations inside them and it's similar to feedback.
There could also be a issue with the output transformer.

Is the amp near fluorescent lights?
Is the amp grounded in the right way?
You don't have the issue when you play the amp lower?
Is the high pitched noise a continous tone? or is like ping-ping-ping...?
It would be good if you could record something, so I can hear how it sounds.

Hope that this will help you.

sawyer said:

Hey guys, quick question: In the last rehearsal whenever I tried to run the gain at 4'o clock, treble at 2 o'clock, mids at 11 o'clock,bass at 10 o'clock, presence at 2 o'clock and the master at 12 o'clock, plus graphic eq with a V, but without completly cutting the mids, If I pushed the presence or the master volume any further (just for the sake of testing to see how much louder it would get, it was already loud enough to keep up with the drummer with the master at 11 o'clock), the amp would start to give a high pitched noise but not like feedback. I read in the manual that pushing to much presence could cause something like that, but can you guys confirm it? Or is it some other issue?This happened even with the guitar muted. Since I've seen some mesa boogie mark v postd talking of a high pitched squeal I wanted to know if it is normal.

Besta regards,
Ricardo

Click to expand...

Extreme settings in most controls on any Mark amp will throw in unwanted noise, squeals etc, particularly at higher gain settings. As you have stated, Mesa point this out in their well written manuals, so your issue is probably normal

It could point to a tube starting to fail, but it's unlikely if the amp sounds good when the EQ is more in balance

My MKV is the most sensitive amp I own, and through trial and LOTS of error, I found the balance that works for what I do lies between 10 - 3 oclock in almost all settings

Have fun!

Hey guys!

Thanks for your responses.

@2 Boogie:

I'm currently trying to find the best settings for "my sound" , so I was experimenting to see what the amp could do. Either way:

Is the amp near fluorescent lights? No.
Is the amp grounded in the right way? Yes.
You don't have the issue when you play the amp lower? I don't even need for it to be turned lower, if instead of having the presence at 2 o'clock I turn it down to 1 o'clock the issue disappears. Or if I turn down the master a little bit it disappears, it only happens when I cross those levels.
Is the high pitched noise a continous tone? or is like ping-ping-ping...? It was continuous.

The rehearsal was recorded , so I might have that sound in there, when I have the recording I'll try to post it here.

@Chester

I think so too since in more balanced situations the issue does not happen,and from what I've been experiencing , since it's my first MB, this is a very very sensitive amp, but just wanted too check. Either way, I'm gonna order a set of power and pre-amp tubes just in case I have to switch anything out. Can you guys tell me what's the color code of the mark v 25 el84 power tubes? Grey? (I'm not at home, nor will be until monday so I can't take a look at the amp to check )

Hello Sawyer!

It sounds like that if you have too extrem setting, the power tubes start to bee too saturated and becomes too sensitive for external interference.

One thing you can do is change the power tubes (both) and see if this will solved the problem.
Power tubes are very sensitive and if you push them too hard too many times, they go more and more bad and tubes is like light bulbs, if you turn them on and off too many times, they break.

Yes the color code for the power tubes is grey, with a yellow ribbon printed around them.
You can read about this more here:

http://forum.grailtone.com/viewtopic.php?f=16&t=30932
http://mesaboogie.com/news/2012/03/mesa-tube-color-codes-by-randall-smith/

Best luck too you!

99% sure this is normal.

Like you pointed out, it is documented in the manual.

My guess is even a brand new set of tubes would exhibit that with extreme settings like that.

One thing is for sure, if it is a high pitched squeal that comes and goes when at loud volumes when you gain treble and presence are all at extreme settings, and is not impacted by you turning the guitar volume knob on your guitar down, it's a tube that is microphonic.