Mark IV volume drop issue

[Force]

just put in all new power and preamp tubes (Mesa), but still have same issue of volume dropping off suddenly to nearly nothing after I have been playing throught it for a couple of hours. It also does this instantly or after a few minutes if I plug anything into the effect loop (either one). again, i just replaced ALL tubes w/ Mesa tubes (new), and it did not remedy the problem. if i put the amp to standby for a few seconds or more, and then back to play it, it is fine for awhile. ...or if I plug anything back into the effect loop, it will also trigger the volume drop problem again.

any ideas what needs to be fixed?

thanks!

 

[jazzin335]

that is very similar to the problem i have with my 5/50 express. mesa checked the amp found nothing so i played the speakers only thru my peavy ,it did it. so mesa and i figured it was a speaker. wrong new speaker dide it too. nothing left i know of other than the speaker cord to speaker.
any idea. this is crazy. did you find your problem?

 

[Force]

that is very similar to the problem i have with my 5/50 express. mesa checked the amp found nothing so i played the speakers only thru my peavy ,it did it. so mesa and i figured it was a speaker. wrong new speaker dide it too. nothing left i know of other than the speaker cord to speaker.
any idea. this is crazy. did you find your problem?

I re-tubed the entire amp, & then i also tried plugging in a patch cord from the send jack straight into the return jack after receiving that suggestion when I recently called out to the Mesa folks in Petaluma and explaining it on the phone to Michael Taylor at Mesa. He said if there is no volume drop after plugging in a patch cord to both ends of the loop, then the loop is not the problem. He said it could be a tune, probably V2. I later realized it may have been an inferior cable with a jack that was not a snug enough fit, or it could have been the tube. He also said a lot of effects pedals to not have a good signal to be heard in the loop, and that could have been an issue as well.

 

[Boogie'sFrenchLover]

You can start by cleaning the pots, tubes sockets and all the jack !

In the past, I have a similar problem with my Mark2A. I have re-tube the amp with no result. The volume decrease to zero and increase randomly. After cleaning all the contact, all was ok !

Ludo