I need some help I recently bought a Peavey 5150 ii second hand and it was in good condition in the parts I knew to check for example it played fine and all the tubes were glowing the same non of them were brighter than the others. I haven't had any problems with it since I bought it which was about 3 weeks ago but now it randomly makes a noise that I can only compare to the intruder deterrents old people have outside their front door. If you know the object I'm talking about then you will understand my concern. I am quite new to this music gear stuff all I know is that it's not feedback I've been to enough gigs and helped out at enough gigs to know what causes interference and how to stop it. Please help me out I'm lost
Tubes are always the first thing to suspect, and you should have a spare set anyway. At the very least, get a new preamp tube and swap it with the old ones one at a time to diagnose.

Tube glow is not a sign that a tube is working properly.
These amps are kinda noise prone but I'd look at tubes in this case. Keep it away from cell phones, that might be also the cause - at least my friend's 5150 was very particular at picking cell phone antennas at 2-3 feet distance around it
How do I find out what exact tubes are in it so that I can buy the same ones? I also keep all types of electronics well away from it. It's at the other side of my room to my PC and I leave all my electronic products on my PC desk, also when I play I stand back from the head. I'd say I'm a good 2 or 3 feet away if not more
I am not sure what you have but my buddy used JJs throughout and it sounded great.
You can start by getting one 12ax7 from a local music store, any brand will do but JJ, EH are usually good choices and just swap all the preamp tubes one by one. If noise doesn't disappear then it it time to look at power tubes and that might need a tech to rebias them.

This video might be able to point you to where the preamp and poweramp tubes are on the amp:
The preamp tubes will be 12ax7's and maybe a 12at7 in the phase drive position, think the power tubes are 6l6's, but a quick Google search will answer that.

Also sounds like it could be a faulty volume, treble or gain pot. I recently had a similar problem that ended up being a faulty master volume.

Defiantly check the tubes first anything else you may need an amp tech.