Fuse

[pivot]

I might have left the amp on for a couple of seconds while the guitar was unpluged. I heard the volume increase in the head then it cut out and a fuse blew. I replaced the fuse and started it back up with out any problems. We have a gig in front of allot of people this weekend wondering if I should replace the power tubes or if this was because the cable was unplugged from the guitar. Nothing changed in the tone on the head after I put the new fuse in and started playing again. Has anyone else seen this?

 

[jb's 52]

I might have left the amp on for a couple of seconds while the guitar was unpluged. I heard the volume increase in the head then it cut out and a fuse blew. I replaced the fuse and started it back up with out any problems. We have a gig in front of allot of people this weekend wondering if I should replace the power tubes or if this was because the cable was unplugged from the guitar. Nothing changed in the tone on the head after I put the new fuse in and started playing again. Has anyone else seen this?

Close to a big gig and the MV seemingly on the fringe. I feel for you!!!
I've never heard of an unplugged guitar causing a fuse to blow...that's weird.

I don't have any good advice other than cycling through some known good
power tubes and maybe getting some kind of back up.

Good luck!!

 

[pivot]

Im thinking it could be the wall outlet because I unplugged an outlet on the other side of the wall and immediately my fuse blew. I replaced it and the amp worked fine the rest of the night. Just my paranoia kickin in im bringing extra power tubes and fuses for this show :

 

[cradlefish]

Im thinking it could be the wall outlet because I unplugged an outlet on the other side of the wall and immediately my fuse blew. I replaced it and the amp worked fine the rest of the night. Just my paranoia kickin in im bringing extra power tubes and fuses for this show :

I've never had a problem with an amp not having a load for a few seconds or even longer, but it's a good idea have a fresh set of tubes regardless of the situation. You never know during crucial situations.

 

[xyrium]

This is odd. I just logged in to search on this subject, here it was on the front page. I had a problem a while ago with this. The amp would exhibit a very loud hum, frightening even. So, I would put it in bypass. It would cause the speakers to pop loudly when I did so.

So, I changed all of the preamp tubes. It happened again a week later. So, I changed all of the amp tubes. Here we are three months later and it just happened this evening. The amp was sitting idle, completely powered on, guitar plugged in with the volume off (on the guitar). I was upstairs, and heard the very loud hum, ran downstairs and as I was reaching for it, the amp powered off. The fuse doesn't have a split in it, but it has two weird tiny balls on it, and the glass is slightly burned. I'm going to let it cool down a bit, then put the fuse in and power it up, if it powers up. Then I'll order a rectifier tube and cross my fingers.

 

[Authorized Boogie]

This is odd. I just logged in to search on this subject, here it was on the front page. I had a problem a while ago with this. The amp would exhibit a very loud hum, frightening even. So, I would put it in bypass. It would cause the speakers to pop loudly when I did so.

So, I changed all of the preamp tubes. It happened again a week later. So, I changed all of the amp tubes. Here we are three months later and it just happened this evening. The amp was sitting idle, completely powered on, guitar plugged in with the volume off (on the guitar). I was upstairs, and heard the very loud hum, ran downstairs and as I was reaching for it, the amp powered off. The fuse doesn't have a split in it, but it has two weird tiny balls on it, and the glass is slightly burned. I'm going to let it cool down a bit, then put the fuse in and power it up, if it powers up. Then I'll order a rectifier tube and cross my fingers.

Sometimes you cannot tell a blown fuse simply by looking at it. By your description it sounds like you've experienced a shorting power or rectifier tube.

If you install a new fuse and it blows immediately upon powering up it would indicate a shorting rectifier tube - you can test this by putting the amp in the 45 watt (diodes in ch. 1 and 2) or 90 watt setting, pull the rectifier tube, and powering up again. If the fuse holds, its most likely the rectifier tube that was at fault. You can use the amp without the rectifier tube in the 45 watt mode with the selector set to diodes, or in the 90 watt mode - the 10 watt mode will not function without a rectifier tube.

If you install a new fuse and it holds, the rectifier tube may not be at fault - which would indicate a power tube caused the fuse to blow. If the fuse blows when switching from Standby to On - a power tube is shorted. Even a brand new tube may short - tube life is something that cannot be predicted or guaranteed - so don't assume that because the power tubes are new, they are not the issue. To figure out which tube is causing the problem, install a new fuse and power the amp on - when you switch from standby to on watch the power tubes carefully for any sign of arcing or red-plating. If its not evident immediately - I recommend running the amp in the 45 watt mode and testing the way the amp sounds, then swap the inner pair of tube with the outer pair of tubes. Since only the inner pair are in use in the 45 watt mode - if you notice a difference in output, tone, or hum - it will indicate which pair contains the faulty tube. That pair should be replaced. Thanks!

 

[xyrium]

Thanks, great info. I was reading through the manual and once I get a new fuse, I'll be looking at the tubes as I power on from standby. I'm hoping this is indeed the rectifier, as the power tubes are only a few months old with low use. I may order a rec tube anyway, can't really hurt since it's the only tube I didn't replace yet.

 

[pivot]

The problem was not the amp it was the outlet. The practice space isnt wired the best Played the gig and many more after that everything is solid. Thanks everyone for the responses. The fuse saved the amp from killing itself

 

[jb's 52]

The problem was not the amp it was the outlet. The practice space isnt wired the best Played the gig and many more after that everything is solid. Thanks everyone for the responses. The fuse saved the amp from killing itself

I think I have the same problem. Fuse blew last night, stuck another
fuse in and it came back up fine. Didn't have time to troubleshoot
because our rehearsal studio time was up.

The power tubes looked fine, but I'll double check 'em today and
I'll take a look at all the pre-amp tubes as well. I was in 90W so I
don't think it's the rectifier tube.

I do have a Friday the 13th gig and I don't wanna use my back up amp...hehe.

Wish me luck!!