Blows fuse

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OddvarR
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Blows fuse

Post by OddvarR » Thu Aug 21, 2014 2:13 pm

Hi. I have a Metro JMP 50 w plexi which I bought seceond hand this summer. It's been working great till it suddenly started to blow the mains fuse, right when I turn it on. Any suggestions: I have tried to change the El84 and the rest of the tubes, but same thing happens?

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Norway.

stef
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Re: Blows fuse

Post by stef » Thu Aug 21, 2014 11:04 pm

Did you check the bias, PT?

OddvarR
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Re: Blows fuse

Post by OddvarR » Fri Aug 22, 2014 3:15 am

Hi and thanks, but I don't know how to do that?

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VelvetGeorge
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Re: Blows fuse

Post by VelvetGeorge » Fri Aug 22, 2014 10:33 am

Your Metro 50 should have EL34 tubes, not EL84. Please double check that.

To troubleshoot:

Pull the output tubes and replace the fuse. Does it still blow?

Remove the HT fuse. Still blow the mains?

Most common reasons a working amp will start to blow the mains fuse are:

an output tube shorts

a diode in the power supply shorts


george
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OddvarR
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Re: Blows fuse

Post by OddvarR » Fri Aug 22, 2014 10:36 am

El34's offcourse, but I'll check testing you suggest.

The two speakeroutputs by the way, are they f x 16ohm when using both or do the change the ohming?

OddvarR
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Re: Blows fuse

Post by OddvarR » Fri Aug 22, 2014 11:25 am

Whatever I do according to your suggestions the fuse blows.

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