Road King 2 channels 3 and 4 have no volume

I'm not sure what happened but after switching V3 and V4 and a few days of playing all of the sudden I have super low volume on channels 3 and 4. Its not V3 as I have swapped it with V2 to see if it makes a difference and channels 1 and 2 sill work and channels 3 and 4 have no volume. I tried dropping in another tube i had laying around and its still the same. One thing I did notice is that the filament is not orange just dark and V2 and V3. I'm not sure if thats normal or not for them tubes but V2 must still work as its the tube for ch 1 and 2.

I want to clarify so as not to confuse, Loop Solo switch is bypassed, I'm in diode mode for all prees, 2x6l6 for all pres,speaker A for all pres, reverb all the way down for all pres, loops switch is off for all pres, all knobs are set at 12 oclock for all pres and i have tried all positions for channels 3 and 4 for voicing and i still have no volume there. I have swapped 3 known to work tubes and still no change.

So i swapped out V2 and it fixed it, odd that it went bad after I swapped out V3 and V1 but meh. After dropping the old tube into V2 the only issue I have is some microphonics at extreme gain settings. It squeals even with guitar volume turned down. Need to find out what best tubes for each slot is but it works now.

I had this very thing happen and it like you found was a blown preamp tube. It has happened twice and both time it was that the cap I think was too tight because it was hard to put down and i swapped it with another and both times my Mullard NOS blew up. I was pissed as ****. Now I just leave them uncovered. Since amp is mostly in my home studio its not really an issue but I dont know why that metal can is so hard to put on. Beware of that.

So from what I have read V3 and V5 of the RK2 need to be tougher tubes, I have read, Chinese, Ruby or most short plat or non coiled heater elements. I am also reading this is an even bigger problem when in spongy mode, I am always in this mode myself. I dropped a new Mesa tube, they don't seam to be labeled Chinese or Russian anymore and its part number 750150F. My amp has never sounded this smooth. I'm gona get a Ruby RUBY 12AX7AC7 HG+ For V1 and a RUBY 12AX7AC5 HG+ for V2 also. Gona look around and see whats best for RK2 PI tube. I don't think it was the cans on the tubes that did it to ya from what I am reading. I wish I would have known about all this back when I bought it, good thing i never had to change tubes till now.

It was V1 the first time. Then I moved that can to a different one same thing. I have not had any problems since I left em off. Who knows.