Mark V - Sound/tone fade issue

[fjk1138]

Update: The tech could not reproduce the problem, and the store supposedly tried it for 2 hours and also could not get it to fail. Neither tried replacing any preamp tubes since they heard no problems. Am I losing it, or is there some other factor at work here that would cause it fail at home and not the repair shop? I've exhausted every possibility as far as I can tell.

Also....Called Mesa and they suggested maybe V5, then V4, but I cannot pick it up until Saturday, so I cannot try this now. Will post results asap.

 

[BostonRedSox]

Update: The tech could not reproduce the problem, and the store supposedly tried it for 2 hours and also could not get it to fail. Neither tried replacing any preamp tubes since they heard no problems. Am I losing it, or is there some other factor at work here that would cause it fail at home and not the repair shop? I've exhausted every possibility as far as I can tell.

Also....Called Mesa and they suggested maybe V5, then V4, but I cannot pick it up until Saturday, so I cannot try this now. Will post results asap.

You aren't losing it man. I am sure that it is a preamp tube issue. I had a similar issue with my Roadster a long time ago that made me similarly insane. My problem was that I never owned a Mesa before and never had tube issues with my Fender amps (which have less tubes). Anyways, the techs should've detected something if anything else was causing the problems.

With tubes, as the amp heats up, if a tube has a weak connection within, the heat can cause things to separate and cause any number of audible issues. The key here is to find the bad tube. If you told Mesa the issues you were hearing, switch both V5 and V4 as directed and move on and play confidently. You could switch out each tube individually and wait, or switch out both. Keep the tubes in two separate bags and mark the bags by which V-slot the tubes originated from. If the issues persist, call back Mesa and ask them for some more troubleshooting tips. Intermittent issues are the most difficult to solve, but you've done the hard part. It may seem troubling that Mesa can't direct you exactly as to which tube to switch out, but this is the problem with intermittent tube issues. Chances are that you have a faulty tube. Like I stated before, your best bet would be to change out V4 AND V5, and if you have further issues, try other preamp slots. More or so likely, if issues persist, if wasn't one of the V4 or V5 tubes.

I would buy three preamp tubes -- two for V4 and V5, and one just in case. Play away and have fun. If the problem comes back, try the other slots. Be patient and enjoy your amp and stop thinking there is something more wrong with it that is going unnoticed.

Believe me, I've had maddening issues too. When I bought my Roadster (new), I had a weird reverb tank issue that was bewildering a Mesa tech. After a couple of appointments we found out the hard way that there was a weak wire connected to the reverb tank. Everytime the tech would reset connecting the reverb tank back to the amp, things would seem to be solved. Anyways, the issue was solved and believe me, that was a freak issue at best. Chances are good that you have a preamp tube that is going wacky and needs to be switched out. No biggie really.

Good luck!

 

[Rkorn]

Could this be electricity related?
With bad electric power Mesa Boogie suffers a lot... And it is quite noticeable in the tone and volume!

 

[Adambomb]

The amp would blow a fuse if it was electricity problem. Maybe them techs are stupid...? I have met plenty of them. Just chill and get ur amp, and troubleshoot all preamp tubes man....that simple.

 

[fjk1138]

Well, I give up. The tech had it, the store had it. Both claimed to have tested it extensively and could not replicate the fault. I was told by the store to bring it back in if it fails again and they would send it to Mesa. So far, I have played it for the past 3 nights for about 1-2 hours each and it has not failed. I really don't know what to make of this, but I am wondering if maybe they replaced something (tube or otherwise) and aren't fessing up. I did notice a slight melting plastic sort of smell FWIW the past two days, but it appears to be gone now. I checked the back, all appears to be fine.

Whatever....if it never happens again so be it. But I know what I heard.

 

[KH Guitar Freak]

I sure hope the voltage of the electricity from your wall socket isn't fluctuating badly...

 

[screamingdaisy]

I really don't know what to make of this, but I am wondering if maybe they replaced something (tube or otherwise) and aren't fessing up. I did notice a slight melting plastic sort of smell FWIW the past two days, but it appears to be gone now.

Since the tech already had it on his bench he probably cleaned everything up as a precaution. The smell is probably the tubes cooking off residue they aquired during the cleaning (this is normal and won't hurt the tubes).

 

[smooth55]

Did your problem ever re-occur? I'm having similar issues of volume fading out with my recently acquired used DC-5 combo.

 

[stevegit]

Can you help guys.... I'm finding I'm having to crank My Mesa Mark 5 head higher than normal at gigs. At home I tried comparing Mark V to my Mesa single rec 50. I had to mute my guitar strings and in turn turned each amp up to full blast. My Mesa single rec was twice as loud as Mesa mark v in 90watt mode channel 3 mk 4 mode. I've even turned the fx level full up too. Everything works great on mk 5 but at gig levels I've had to crank master vol at 4 o clock going through a mesa 2x12 cab or marshall mini 4x12
All four 6L6s have been replaced, could it be the rectifier valve or best to change all preamp valves. Help please.. Steve

 

[Adambomb]

Can you help guys.... I'm finding I'm having to crank My Mesa Mark 5 head higher than normal at gigs. At home I tried comparing Mark V to my Mesa single rec 50. I had to mute my guitar strings and in turn turned each amp up to full blast. My Mesa single rec was twice as loud as Mesa mark v in 90watt mode channel 3 mk 4 mode. I've even turned the fx level full up too. Everything works great on mk 5 but at gig levels I've had to crank master vol at 4 o clock going through a mesa 2x12 cab or marshall mini 4x12
All four 6L6s have been replaced, could it be the rectifier valve or best to change all preamp valves. Help please.. Steve

Could be Phase Inverter tube. Anytime you have fading or volume loss like that the PI tube, speaker cable, output tranny, and check all the obvious connections and try with differnt cabs and cables. Move the PI tube while on, and if volume jumps back up, it's either PI tube or tube socket gone bad. Good luck!

 

[Authorized Boogie]

Incoming voltage can definitely have an effect - and if you can't replicate the issue in different locations then it could definitely be the cause.

Another common problem, as stated above, is preamp tubes. Take a new/known good 12AX7 and swap it into EACH position, one position at a time.

To test power tubes, put the amp in the 45 watt mode and swap the inner pair with the outer pair. If there is any difference it could point towards a bad power tube.