amp blowing fuse

  • Powered up my tube amp this a:m  and almost immediately the fuse blew. It happened so quickly I don’t even think any voltage was reaching the tubes  Put the fuse from the other mono in and got the same result.   Going to buy some more fuses now and my question is could a bad power tube cause this?  Or does it seem there’s some other internal issue  ?  The tubes are brand new so I don’t think that’s the case but I guess it’s always possible   The amps have been in hibernation for almost two years 
Yes, bad tubes could cause this. Pull the speaker cables off before you do any more experiments.

Swap out the tubes and you'll know. :)

which fuse what is?  Was it the AC line fuse in the IEC connector?  If so, a bad tube shouldn't blow that. That's more likely a switching surge issue.  Now if one of the tube fuses blew then yes, sounds like a bad tube.
There’s only one fuse externally on the amp. Pretty sure it’s for the tubes. There’s a jewel power indicator lamp that glows for about one second before the fuse blows.  I’m not hearing any noise through the speakers when this happens. You’re saying I should disconnect the speaker wires while experimenting?  I thought that was bad  don’t the amps want to see a load?  There’s also a 6sny7 tube. Could that also cause this?  
Try powering up without the power tubes, if it stays on, then tubes, if not, something else.
With a tube amp you should always keep the speakers hooked up. You are correct, tube amps need a load or else they can be damaged!
  • Very strange. Just picked up some fuses at Lowe’s and swapped the tubes from the amp that powered up and now it powered up. So I’m thinking it was the tubes. So just for the heck of it I put what I thought were the offending tubes in the other amp and that powered up as well. I’m thinking that the shorting jumper was loose on the one speaker and tightened that up. Could that have been the issue. Thanks for all who chimed in. Now I’m out $2.00 for fuses LOL
Just an update,  Problem was a bad rectifier tube  swapped it out and all seems well. now breaking in my new Tung soul 7581 tubes