2. amps-preamps
  3. 147413-57

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 
metman
three_easy_payments's avatar
three_easy_payments
2,097 posts
 
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.
metman OP
233 posts
 
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?  
stevecham
3,340 posts
 
Try powering up without the power tubes, if it stays on, then tubes, if not, something else.
yogiboy's avatar
yogiboy
5,482 posts
 
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!
metman OP
233 posts
 
  • 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
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