Yeah, I've had ( and still do) crappy experiences with 5150's
I've had 3 all over the years and all of them ( the last one 2 weeks ago, still being serviced) broke in the same way. Noise buildup, you put the amp on standby because of fear and then the amp blows the fuse, you change it, it makes a really big spark on the 4th power tube and it's blown up.
I love the sound but it's unreliable in my experience.
I wish I could go buy another amp that wasn't giving me those chills whenever something weird comes out of the guitar cab, but when I bought it, it was the only thing I could reach in terms of budget, this last time was because I love the sound and boom again
I keep telling myself "you should have bought the engl/laboga/krank instead" quite often
P.S. I'm using it for band practice/rehearshal duties, running from a furman pl8 so the power doesn't have spikes, or it shouldn't