First time posting. A little background to my question: I picked up a Scott 299C a couple of years ago without really knowing what I was doing. I heard they were a good amp to try out that tube sound for not too much $, so I figured why not, I've been curious for a long time. The amp played well, but with quite a bit of hum and crackle on one side. Some "expert" told me to change out the original 7591 tubes with new ones and that would solve the problem. So I got some brand new (Russian I think) 7591s and put them in, then fired up the amp. After about a minute there's a really BIG POP and the amp goes dead - no sound at all! This freaked me out so much I immediately unplugged it, wondering what kind of god-awful damage I unwittingly inflicted. I just couldn't deal with it and put the poor thing away for probably a year and half and just went back to this Yamaha solid-state amp that I have. The Yamaha is big and loud, but not amazing. Anyway, to make a long story longer, eventually I decided to take the Scott somewhere that knows this stuff and find out what the problem was. I looked on the web and called around for someone/place local (I'm in the SF bay area). So there's just not a lot nearby except for some guitar amp guys (I wasn't sure if they would really know how to treat this old hi-fi stuff and didn't want to make another mistake). Since it seemed this was going to be more of a process than I thought and since it had been so long since I last tried it, I decided to clean the pins and reseat the original tubes (about all I know how to do), then try the old Scott once more before just taking it SOMEWHERE. I hooked up my JBL Century 100s (more vintage!) and pulled the power knob, expecting nothing, or for it to blow up! Now I have no idea how or why, but the Scott powered up and worked! Not only worked, it sounded great! I mean so bizarre I can't even believe it myself. I've been using it now for about 3 months and it sounds amazing. The hum/crackle problem is not there now. The sound really does live up to what others have said. Hopefully I'll never have to go back to solid-state again. Here's the question: Should I just never mess with the tubes in this amp again? Was it that it just didn't like those Russian tubes, or... ?

I'm very curious how long I expect this old (not sure how old) totally original amp to play well if I just leave it alone.

Any insight much appreciated!

theo