Bugera 333xl blowing mains fuse

[Danglin' Fury]

So I had a problem with my Bugera recently. The PSU6 board smoked a couple of thermistors. No worries, I took one off of a dead Bugera 1960 I have laying around. Turned the amp on and it sounded awesome! No bad smoke smells. Lol! Played amazing. I've been using E34L tubes in the power section. I was wanting to do a comparison with JJ EL34s... put those in and after I turned the standby off, there was this humming noise and a zzzzzip! sound. Blew the mains and there is now that ozone smell around the power switch/ power transformer area. I'm going to troubleshoot it very soon as I'm itching to play but work, kids, etc. IF I do need another power transformer, is there a cheaper option out there than the Mercury Magnetics $200 transformer? Can I just swap the transformer from the dead 1960 and use it? Thank you for looking. I'm looking forward to your replies!

[Enzo]

Wait. You fixed the amp, and it worked fine, right? Then you put different tubes in it and it went PFFT. Why oh why would you then think it needed a transformer instead of thinking the new tubes were faulty?

[Danglin' Fury]

Well, I took the tubes out and there is a very strong smell, you know, that burnt electronics smell, emanating from the area of the power transformer/power switches. So something smoked bigtime in that area. The tubes were actually what I suspected at first. Then the smell hit me. After I had changed the psu6 board, there was absolutely zero smell in the amp. As soon as the mains fuse blew, there it is. I'm sooooo hoping it's the new tubes. But that distinctive smell is only in the area of the PT...

[Jon Snell]

Remove the valves, (EL34s) fit a new fuse of the correct value, switch on ... what happens.

[Danglin' Fury]

I will do exactly that when I get home. And it wasnt that I just immediately jumped to the PT, a whole slew of other ideas came to me. But I was trying to prepare for worst case scenario and how much it would cost me

[Enzo]

Bad power tubes VERY often burn up a screen resistor.

Do you know that the various components have characteristic smells when they burn up? Oh, not 100%, but mostly. An experienced nose can tell the difference between a burnt transistor, and a burnt resistor by the smell. And yes transformers too. And of course any old timer can tell instantly when a selenium rectifier burns. NOTHING else smells like that.

[g1]

I would think the power switch may have fried. Just bypass it (for test purposes) and use the AC plug to connect/disconnect power.

[Danglin' Fury]

I was kind of thinking the power switch too...that was one of the other things I thought of.. thank you guys! I will bypass it when I get home after I fire it up with the power tubes pulled. The smell was very strong by the switch. Fingers crossed!

[g1]

In this unit the power switch is after the fuse, so it is a possible cause of the fuse blowing.

[Danglin' Fury]

Hey all... so I found my issue. Apparently in my house, it is actually multi-family dwelling... I live in a very large basement (2000 sq.ft) a family lives above me, and there are 4 apartments built onto the backside of said house... the owner is too cheap to hire an actual electrician so he works his maintenance guy to death. The guy is certified but dude has 30 properties....anyway. point is, the wiring is shite. A very large surge hit the thermistor board and took the power and standby switches with it. I replaced all 3 components and voila! Amp works great!