# Amp won't turn on (blown fuse?)



## Hybrid138 (Oct 3, 2011)

I did a quick search and couldn't find what I was looking for. I turned my amp on today and went away for a second and when I went back the power light wasn't on. I remember it turning on at first, but I'm not 100% sure. I haven't changed tubes or done anything drastic. I check all cables and power sources with no help. I checked the fuse and it had some brown marks on it. I'm hoping it's the fuse. I'm taking it to Guitar Center tomorrow. Any suggestions as to what may be wrong?


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## asher (Oct 3, 2011)

That does indeed sound like a blown fuse, which is usually caused by a tube on its way out.


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## Rampage (Oct 4, 2011)

More than likely a power tube issue. If a power tube has failed or is about to fail, a fuse should pop to protect the amp from further damage. The first thing I would do is check the fuse(s) with a multimeter to see if it is indeed open, and if it is, I would replace the fuse(s) and tubes and re-bias the amplifier.


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## Hybrid138 (Oct 4, 2011)

The fuse had brownish spots but the filament was still going from top to bottom....


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## Mordacain (Oct 4, 2011)

Hybrid138 said:


> The fuse had brownish spots but the filament was still going from top to bottom....



Brownish spots = blown. Fuse don't necessarily have the filaments broken as, say, a light bulb would.


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## Hybrid138 (Oct 4, 2011)

So if it turns on after I change the fuse, the fuse was obviously blown. My next step would be to check the tubes to see if any were the cause of the blown fuse? How I would check for that?

The amp is my Roadster by the way if it makes a difference.


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## asher (Oct 4, 2011)

Hybrid138 said:


> The fuse had brownish spots but the filament was still going from top to bottom....



Amps use a slow-blow fuse, which is more than just a single filament. This lets them deal with the voltage spike caused by warming up the tubes, which would trip a regular fuse.


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## Hybrid138 (Oct 4, 2011)

Where can I buy the fuses at? They don't sell them at Guitar Center... Apparently I need a 4 amp Slo-Blo fuse?


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## Wookieslayer (Oct 4, 2011)

any hardware / electronics store should carry em. buy 2 for an extra


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## Hybrid138 (Oct 4, 2011)

There are several here

Slow-blow fuses - Fuses - RadioShack.com

Is there a wrong one to pick?


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## yingmin (Oct 4, 2011)

Hybrid138 said:


> There are several here
> 
> Slow-blow fuses - Fuses - RadioShack.com
> 
> Is there a wrong one to pick?



Look at the fuse that you pulled out of the amp. It should list the voltage and amperage on the end, and you can measure it to make sure you're getting the right size.


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## Hybrid138 (Oct 5, 2011)

I found this in case someone searches and finds this topic. 

Fuses: What do they do, why do they blow and what you need to know.


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## dunno (Oct 7, 2011)

Definetely failed power or rectifier tube. Happened to me few months ago. I blew power tube and rectifier tube at once and my amp kept blowing fuses. Tech told me that i fried the tranny. I didn`t want to believe and tried troubleshooting recto myself. Basically what i did is in this awesome video:
Mesa Boogie Tube Troubleshooting 101 Video


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## BabUShka (Oct 7, 2011)

I also think it might be the power amp tubes. Hopefully a retube and a new fuse will solve your problem. Take that as a positive thing, fresh tubes can give you a more organic sound and you'll know that it'll be a long time till next retube =) 

One thing is for sure, that there's always a reason for a fuse to blow. I had a simular problem with one of my tube amps, and it turned out the rectifier was broken. 
The amp doctor knows what to do, dont worry


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## GuitaristOfHell (Oct 7, 2011)

Check power tubes and fuse. Could be either.


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## Hybrid138 (Oct 8, 2011)

I can use any brand of power tubes right? As long as they are the same type I don't have to bias


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## asher (Oct 8, 2011)

Hybrid138 said:


> I can use any brand of power tubes right? As long as they are the same type I don't have to bias



I'm pretty sure different brands run at (somewhat) different voltages, which means a small bias tweak might be optimal, but it's very likely not necessary, and you should just make sure some new tubes work first.


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## Hybrid138 (Oct 22, 2011)

I also have to change the other tube in the pair correct? Like if tube 1 is blown I have change 1 and 4?


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