more VT40 fun

[methodofcontrol]

so, i solved the mysterious ext. speaker jack issue i was having. (see other thread for details),
the only other issue this amp had was at high volumes i would get a popping/cracking sound if i really dug into the strings. when i plug in a master volume pot in the ext. amp jack, i can crank the pre-section as hard as i want without getting any popping/cracking noises. so i decided that i might need new power tubes. granted, i didn't want to play the amp super loud to test my theory so i thought, "hey...why i don't plug in a pair of EL84 adaptors so i can try new power tubes at more reasonable volumes! the amp should be respond the same, right?"
i plug in a pair of GT Substi-tubes and turn the amp on, the white noise of the amp being on sounded louder than i remembered, but i thought it was just because i probably had the volume up further than usual due to the EL84's not being as loud. i start playing a little bit and immediately i know something is wrong. everything i play is coming through, but at volumes barely above speaking level and with almost no break up. similar to how it sounds when i plug the master volume pedal in. makes me think the power amp is somehow not doing what it's supposed to, because that's where all the break up occurs on these amps. you have to play them loud to get it because the pre amp is so clean.
i turned the amp off within 30 seconds of checking out the EL84's, and i smell something burning. it doesn't seem like it's coming from the Substi-tubes or the EL84's, but they're quite hot and the smell goes away very quickly so my nose isn't helping me track it down any more. i figure i blew an EL84 or Substi-tube w/ the crazy voltages in the VT40 and to check i put the 7027's back in to see if i still have a problem. the amp has the same output volume problems it had with the EL84's. w/ the amp volume set to about 5, it should be blowing me out of the room. but as it was i could probably hold a loud conversation over it.
i'm about to open it up to visually inspect for a burnt component. but are there any suggestions as to where i should be looking first?
why would EL84 adaptors cause this issue? or did they aggravate and progress a likely existing issue?
i've been playing the amp regularly (an hour or so every other night) for the last two weeks w/ the master volume pedal plugged in and i haven't had any problems. i only decided to troubleshoot the popping/cracking noise because i plan to run the amp at full volumes in the studio next month. hopefully i can get it back up and running. i pray it's not the OT.
thanks in advance for the help!

[methodofcontrol]

i looked into the amp more last night. i see no evidence of any burnt components or anything wrong at all, so i plug it in and turn it on w/ the 7027's in place. everything works like a champ. no volume issues. i didn't crank it up because it was late, but i did notice a sort of static-y ghost note when i play certain notes. dissident notes in particular, it almost sounded like a speaker farting out, but it was linked the amp itself vibrating. i could replicate the noise by tapping on the chassis or boards, this seems like a new thing. or perhaps it's linked to the volume issue that was created the other night?