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Blows fuse
Posted: Thu Aug 21, 2014 2:13 pm
by OddvarR
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?
Best from
Norway.
Re: Blows fuse
Posted: Thu Aug 21, 2014 11:04 pm
by stef
Did you check the bias, PT?
Re: Blows fuse
Posted: Fri Aug 22, 2014 3:15 am
by OddvarR
Hi and thanks, but I don't know how to do that?
Re: Blows fuse
Posted: Fri Aug 22, 2014 10:33 am
by VelvetGeorge
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
Re: Blows fuse
Posted: Fri Aug 22, 2014 10:36 am
by OddvarR
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?
Re: Blows fuse
Posted: Fri Aug 22, 2014 11:25 am
by OddvarR
Whatever I do according to your suggestions the fuse blows.