Jeff Seal
New member
Allright guys and gals, I feel compelled to discuss a subject that has been the death of many a fine amp........ fuses!
As most of you know, I am an amp tech and I've seen my fair share of senseless destruction.... But this week alone has triggered me into action to inform the general public about these apparently misunderstood devices...
Fuses are current rated "circuit breakers" specifically designed to protect both you and your gear from unsafe operating conditions. Which means if you should blow a fuse, chances are something bad has happened that caused an excessive amount of current to be drawn. Half the time this can be attributed to external factors that you, the user, have no control over....(power surges, improper wiring at facilities.....and most notably, for those on tour, generators!!) In 95% of these cases, simply replacing the fuse with the correct replacement will get you back up and running with no damage done. (Assuming the external problem has been solved).
However, replacing a fuse with one that is not the same amp rating is DUMB!
The people who engineered your amp (or any other device) know what the maximum current rating is, and specified a rating to ensure proper operation without burning anything up....(most of the time!).....Especially for tube amps!
If your amp has an externally accesible fuse, do yourself a favor and go get some spares now that you don't need them, instead of "panicking" when you do need one. They will have an ampere rating (ex. 3amp) and usually will specify "fast blow" or "Slow blow"....SB for short.
If your amp ever blows a fuse, simply replace it with the same value fuse and if it blows again.....do not keep trying, and take it to a tech.....No one has ever succesfully "powered" their way through an amp problem...EVER!!!!!
No, I haven't just bought stock in a large fuse company, and the "beer can" story (among others) is as follows:
Got a Mesa 400+ Bass Amp in for repair, this baby runs 12....that's right 12....6L6's for output tubes! Amp didn't power up, and a quick check of the fuse revealed the 8amp fuse had been replaced by a small curled up section of a Bud Light can! (amp rating unknown.... :alcoholic ) Further analysis indicated two diodes in the rectifier circuit were shorted, which was the original problem....diodes = $0.65 each, so what would have been a $90 max repair bill now has jumped to almost $500 because the Power Transformer is fried....and it is one massive transformer!...
why????... because apparently a replacement fuse was not readily available, even though it would have blown too, it would not have destroyed the tranny or fried the traces off the PCB. Just would have let the owner know there's a bigger problem.
Although that was the first one this week, I've been getting way too many amps in with incorrect value fuses. Trust me, I am all for a more thorough exploration of amps and more and more people are trying differing tube setups and pushing amps harder and harder....but be wary, fuses are often your only safeguard against meltdown.....unfortunately amp "victim" number two was a priceless piece of history!!!!!...(those with a weak stomach may want to leave now.)
1964 Fender Blackface Super Reverb...... :blackeye: originally blew fuses because the owner was unaware that the "spkr out" jack has to be used before the "ext spkr" will do anything......simple enough....
His solution was a 15 amp fuse which promptly annihilated the power tranny, one of the 70uf filter caps and worst of all......because the transformer didn't burn up fast enough, it fried all 4 original speakers!!!!..........(chain succession failure!)
...the 30 cent fuse never blew!
all he had to do was plug the speaker's into the spkr out jack instead of ext. spkr......... :smack:
Just Fwiw..........
Jeff Seal
As most of you know, I am an amp tech and I've seen my fair share of senseless destruction.... But this week alone has triggered me into action to inform the general public about these apparently misunderstood devices...
Fuses are current rated "circuit breakers" specifically designed to protect both you and your gear from unsafe operating conditions. Which means if you should blow a fuse, chances are something bad has happened that caused an excessive amount of current to be drawn. Half the time this can be attributed to external factors that you, the user, have no control over....(power surges, improper wiring at facilities.....and most notably, for those on tour, generators!!) In 95% of these cases, simply replacing the fuse with the correct replacement will get you back up and running with no damage done. (Assuming the external problem has been solved).
However, replacing a fuse with one that is not the same amp rating is DUMB!
The people who engineered your amp (or any other device) know what the maximum current rating is, and specified a rating to ensure proper operation without burning anything up....(most of the time!).....Especially for tube amps!
If your amp has an externally accesible fuse, do yourself a favor and go get some spares now that you don't need them, instead of "panicking" when you do need one. They will have an ampere rating (ex. 3amp) and usually will specify "fast blow" or "Slow blow"....SB for short.
If your amp ever blows a fuse, simply replace it with the same value fuse and if it blows again.....do not keep trying, and take it to a tech.....No one has ever succesfully "powered" their way through an amp problem...EVER!!!!!
No, I haven't just bought stock in a large fuse company, and the "beer can" story (among others) is as follows:
Got a Mesa 400+ Bass Amp in for repair, this baby runs 12....that's right 12....6L6's for output tubes! Amp didn't power up, and a quick check of the fuse revealed the 8amp fuse had been replaced by a small curled up section of a Bud Light can! (amp rating unknown.... :alcoholic ) Further analysis indicated two diodes in the rectifier circuit were shorted, which was the original problem....diodes = $0.65 each, so what would have been a $90 max repair bill now has jumped to almost $500 because the Power Transformer is fried....and it is one massive transformer!...
why????... because apparently a replacement fuse was not readily available, even though it would have blown too, it would not have destroyed the tranny or fried the traces off the PCB. Just would have let the owner know there's a bigger problem.
Although that was the first one this week, I've been getting way too many amps in with incorrect value fuses. Trust me, I am all for a more thorough exploration of amps and more and more people are trying differing tube setups and pushing amps harder and harder....but be wary, fuses are often your only safeguard against meltdown.....unfortunately amp "victim" number two was a priceless piece of history!!!!!...(those with a weak stomach may want to leave now.)
1964 Fender Blackface Super Reverb...... :blackeye: originally blew fuses because the owner was unaware that the "spkr out" jack has to be used before the "ext spkr" will do anything......simple enough....
His solution was a 15 amp fuse which promptly annihilated the power tranny, one of the 70uf filter caps and worst of all......because the transformer didn't burn up fast enough, it fried all 4 original speakers!!!!..........(chain succession failure!)
...the 30 cent fuse never blew!
all he had to do was plug the speaker's into the spkr out jack instead of ext. spkr......... :smack:
Just Fwiw..........
Jeff Seal
