Do I need new preamps on my Mark IV??????????

Recently when I was playing my Mark IV the gain just depleted a lot and it sounds like clankey crap. When i have the volume nob of the guitar closed off it makes weird hissing noises and feed backs like crazy. I'm almost positive the preamps haven't been replaced because the power tubes that came with it were the late 1990s when it was made (1998). I dont think its the power tubes becaue i replaced those at christmas. I'm thinking all these things are the cause of the preamps. But i was thinking some expertise opinions would help me make the decision.

did you try lightly tapping on the preamp tubes with a pencil while its running?

you should hear a crackly kind of sound, almost reminds me of having water stuck in your ear.....if so, bad tube(s).

I did the pencil thing and it didn't do anything but what explains the low gain. I also noticed that when i turn my lead gain around it makes a fuzzing popping, mabye my pot is dirty?
thanks

not sure man, I'd say take it to a Mesa tech. My Mark IV hasnt run 100% since the day I got it. My dumb-***.....now that my band isnt playing any shows, and I have a backup, I should have sent it to mesa a long time ago. :?

The pencil test doesn't always work. Start swapping out preamp tubes one by one. If all else fails then take it t a tech.

I just ordered new preamps so hopefully taht will solve my problems im 95 percent sure its my preamps