So I'm having a problem with my recently acquired Vox AC15HTV1 amp. It's on of the heritage handwired series from a couple a' years back. I've had it for a month now and it's been working well, and sounding great, until a few days ago. I turned it on as normal, and a few seconds later there was a light crackle, and the whole thing turned off. The mains fuse had blown, so I replaced it with the correct one, started it up and the same thing happened again. I did some research and saw that the rectifier or power tubes could be the cause so I took the rectifier out, put a brand new fuse in, started the amp and it was fine... no fuse was blown. So, happily, I assumed it must've been the EZ81 rectifier, so I went and ordered a replacement. Recieved that yesterday, (brand new JJ EZ81), popped it in, started the amp, everything was fine for maybe 30 seconds, the tubes were all glowing, and then a slight crackle along with blue sparks inside the recifier tube happened for maybe 3 seconds and the power died again! Again, it had also blown the mains fuse. Any idea in what could be up with this? I'm out of my depth with this, and am on the verge on taking it to a tech, but just wanted to check in with you knowledgable folks first incase I've missed something obvious, or something cheap to repair. Thanks in advance, Xan P.S: I should also point out that although the amp was running well before this, it did have some moments of odd behaviour. ie, the power light would go off randomly even though the amp was still running and performing perfectly. And, in pentode mode there was always a loud hum, loud enough that it seemed odd to me. But switching to triode mode made this disappear completely and the amp was as quiet as a mouse!