Author Topic: amp keeps blowing fuses?  (Read 3431 times)

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Offline cosmic erosion

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amp keeps blowing fuses?
« on: October 19, 2009, 08:45:57 am »
my sunn studio pa is giving me trouble for the first time after 2 years of no trouble whatsoever. any help on this would be much appreciated. we have a few dates out of town two weekends ago, so i send both my amps into my tech to get looked over. nothing worse than them shitting out on the road. mind you, i've done business with the guy for almost 6 years now and he's always done an amazing job. i've recommended him to others and same thing. awesome guy.

so i send them in. he rebiases the studio pa bc it's drifted a little off over the two years i've had it. understandable. other one needs a new rectifier tube. they come out with a clean bill of health. i'm pumped.

first show, we play, but when i go to turn the amps off after the set, i notice the studio pa isn't on. hmmm. weird. it's late, so i say i'll just mess with it tomorrow. i pull the fuse and it's blown. awesome. nothing big. just a fluke. call my tech and explain to him what happened. i put a new fuse in. powers up. sweet.

2nd night. warming them up, probally ten minutes on standby, studio pa turns off. i go wtf? kinda pissed now. but at least i have the other head. halfway through the first song, the volume starts fading and it shuts off. now i'm really pissed. one of the bands was cool enough to let me borrow a vtm to finish our set. we play 3 songs and call it a night.

monday comes(last week). i call him and tell him what happened. he's flabbergasted. like said, no probs ever with his work. he says bring em in. i tell him, i need at least one of them back by friday bc we have shows this weekend as well. no prob.

studio pa blew an output tube he says. i say cool, if you can get what i had in there, that would rule bc i love its tone. coliseum pa had a filter cap go out. now i know old amps, or any, will have things like this happen, but these were in a week before and given a clean bill of health.

he doesn't have the tubes in stock, but will order them. he says he'll lend me a pair of his own personal 6550's to use till mine come in so we can play. that's very awesome of him. so i go pick up the studio pa on friday. i ask him, well, what'd you put in there? he says some nos ge 6550's i've had since the early 80's. i say omg, i've been wanting to try those in there, but can't swing the price. he says i'll cut ya a deal on em if ya want em. i say let me try em out. i speed home and plug it in. o man. sorry, off topic. amps fine. sounds great. excited for our show on saturday.

get to the show, plug the amp in to warm it up. ten minutes in. same thing. turns off. WTF? now i'm real pissed. first bc my amps messed up again and second i'm worried i just blew up those tubes. luckily, i had a spare fuse he gave me. put it in and cross my fingers. makes it through the set. i played it a bit yesterday, no probs.

any suggestions on how to handle the situation and any thoughts on what could be the culprit? my band wants me to sell the heads and get something else. mind you, up till the studio pa went into the shop two weeks ago, no trouble for two years. i've changed nothing in my rig. i def don't wanna sell them, i finally am happy with my tone except for this dumb stuff. thanks!!!! sorry for the long winded post, i just wanted to make sure i covered everything.

Offline mckinnon audio

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Re: amp keeps blowing fuses?
« Reply #1 on: October 19, 2009, 12:32:41 pm »
   Hi there,it's taking out the main fuse,so it's drawing a lot of current whatever it is.If you have replaced just one filter,I'd replace them all,even the one in the bias circuit,check tube sockets for arcing,look for bad connections on the transforme leads,you'll find it eventually,goodluck Mel.

Offline cosmic erosion

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Re: amp keeps blowing fuses?
« Reply #2 on: October 20, 2009, 09:09:25 am »
thanks!

Offline Isaac

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Re: amp keeps blowing fuses?
« Reply #3 on: October 21, 2009, 11:26:54 am »
Also, make sure that the replacement fuses are of the slo-blo type. That caused me some issues a year or two ago.
Isaac

Offline scotzoid

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Re: amp keeps blowing fuses?
« Reply #4 on: October 22, 2009, 02:20:30 pm »
+1 for Isaac. I think most fused Sunns specify Slo-Blo; I'm pretty sure my Sorado does.

Offline cosmic erosion

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Re: amp keeps blowing fuses?
« Reply #5 on: October 22, 2009, 03:30:54 pm »
well i think between my tech and i we've figure it out. the fuses were def the right ones. we determined one of my cabs has a messed up speaker causing it to blow the fuses. also, after changing the rectifier tube all is good so far. tho, i did score a pair of a pair of nos ge 6550 tubes for $120 outta of this from my tech. he rules so hard. he def has gone above and beyond on this.