Power or Volume drop in Express 5:50

[shendrie]

Hi All,

I have a 5:50 express and tonight when I fired up my amp at rehearsal the clean channel was much quieter than usual... to the point where it was not usable in a moderately loud band situation (normally it is fine). The tone also seemed to have lost some "umph". Channel two was fine, lots of volume but I primarily use channel one with pedals for my tones.

I double checked all the settings and switches and everything was fine. Any thoughts... I am thinking it may be tube related (who knows which one) but was not sure since channel two works fine.

thanks,
Stu

 

[Newysurfer]

Hi All,

I have a 5:50 express and tonight when I fired up my amp at rehearsal the clean channel was much quieter than usual... to the point where it was not usable in a moderately loud band situation (normally it is fine). The tone also seemed to have lost some "umph". Channel two was fine, lots of volume but I primarily use channel one with pedals for my tones.

I double checked all the settings and switches and everything was fine. Any thoughts... I am thinking it may be tube related (who knows which one) but was not sure since channel two works fine.

thanks,
Stu

inspect your tubes closely.
The Manual gives instructions for doing this

 

[Axxis]

Alright Ive been searching for basically the same question and I can't find the answer so here goes.
I'm getting basically the same problem as this guy except it's not the whole channel. I have an express 5/25 and my channel one is just fine. In channel 2 the burn is loud and sounding great but when i switch into blues mode the amp gets very soft and loses a lot of volume. Channel one clean or crunch either one is basically the same volume as the burn in channel 2, the ONLY setting that loses that much volume is the blues switch. Makes no sense to me. If it was a tube shouldnt the whole channel be losing volume? This just happened last night so I havne't had a chance to play with it much but any help would be much appreciated.

 

[MrMason]

It could be that the burn mode doesnt use the same tube as the blues mode. On some amps one mode will use one side of a single tube, and the other side on a different mode.

 

[Axxis]

well I swapped the power tubes out or rather exchanged one with the other and it's still doing it so should I try swapping some preamp tubes or could this be more of a serious problem?

 

[MrMason]

You should've swapped preamp tubes FIRST; one channel fine and another not is more an indicator of a bad preamp tube, not power amp tube.

 

[Axxis]

Well I can put the power tubes back in their original place and then swap preamp tubes but just to clarify the whole channel isn't acting up. Channel one is completely fine and channel two runs fine when the selector switch is in burn mode. But when i put it in blues mode the volume goes way down without adjustin knobs. Now I really dont know jack about tube amps with this being my first one so I had no clue that preamp tubes would be more likely to indicate the problem. THanks again for the input guys, i still haven't figured it out.

 

[Axxis]

Sorry to double post but I would just like to say I have no idea how this is wired up. It's the mesa express 5:25. Even though I'm in channel two, if i hit the switch from blues/burn does that change up what tubes i'm using? Thanks again.

 

[Don]

Yes. There's a tube task graphic in the manual that explains it all pretty well.
If you don't have the manual you can download a PDF of it on the MESA/Boogie website.

 

[Axxis]

Thanks a lot bro, ima go check it out.

 

[MattG]

I seem to be having the same problem as Axxis with my Express 5:50.

Channel 1, both modes (clean and crunch) is fine. Channel 2 Burn mode is fine. Only Channel 2, Blues Mode I'm getting a major lack of volume.

I've rotated a single new preamp tube into each slot with no change.

Anyone ever solve this problem?

Thanks!
MattG

 

[Skully]

I recently had this happen to my 5:50, it was a bad preamp tube. Also it might already be known but while swapping it did not like Chinese tubes. The tube that ended up being bad had the majority of the writing missing off of it, very noticable comparing it to the other 12ax7's, almost like it was burned off or rubbed off somehow.

 

[MattG]

I recently had this happen to my 5:50, it was a bad preamp tube. Also it might already be known but while swapping it did not like Chinese tubes. The tube that ended up being bad had the majority of the writing missing off of it, very noticable comparing it to the other 12ax7's, almost like it was burned off or rubbed off somehow.

Skully,
Do you remember which tube? It had to be V1, V2 or V3.
Was it only in Burn mode that you saw the problem?