So a few months ago I bought a used Fender Hot Rod Deluxe. Not the greatest amp in the world, but it gets the job done. Anyway, about 2 weeks ago, I was practicing at home when the amp made a horrible horrible sound and then went dead. I checked and sure enough ... blown fuse. So I replaced the fuse and went on my merry way. I thought it was a little odd that the fuse blew at such a low volume (I had it on like 2), but it was easy enough to get a new fuse so I didn't really worry about it. The amp has been working fine for the last couple of weeks. Until a few days ago. When I fire it up, it works great for about 30 minutes to an hour ... Then it starts making a nasty crackling, rumbling, hissing sound. I'm new to all this wired up, electrofied stuff, so I'm not sure what's going on, and some help would be appreciated.
When the crackling starts, if I put the amp into standby, the problem goes away. That leads me to believe it could just be a case of a worn out tube(s). However, (and this is where my lack of knowledge and experience may come shinning through) the blown fuse from a few weeks ago concerns me, and makes me wonder if the problem I'm having isn't something else .. something electrical.
Finally, some tube questions, in case it does turn out to be just a case of bad tubes. If I change out the preamp tubes, should I (or do I have to) replace both of them, or is it acceptable to just replace the one offending tube? I know changing out the main tubes requires re-biasing and such, which is a task that I'm not up to myself. But if I understand correctly, I can just change out the pre-amp tubes on my own with no further work required. Is that right?
Thanks in advance for all your help!