Hello all.What is the best kind (fast/slow blow) and amp rating fuse to use for the B+ just in case of short etc.. (to protect rectifier /transformer etc..)....for 7- 9 tube Push/pull radio ..or how do you figure this out.Do you add the maximum current output of all the tubes ,including eye tube(6U5 etc.), (except the rectifier) for maximum current ???

Chris:

I like to use a slo blo fuse. If you know the rated power that the receiver takes ( sometimes listed as the number of watts on the back of the receiver), you can figure the amps. P = IE, P (watts) = I (amps) X V ( volts). The I would rate the fuse at appx 2x higher that, for example for a 2 amp radio draw use a 4 amp fuse.

Lou

:Hello all.What is the best kind (fast/slow blow) and amp rating fuse to use for the B+ just in case of short etc.. (to protect rectifier /transformer etc..)....for 7- 9 tube Push/pull radio ..or how do you figure this out.Do you add the maximum current output of all the tubes ,including eye tube(6U5 etc.), (except the rectifier) for maximum current ???
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:Chris:
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:I like to use a slo blo fuse. If you know the rated power that the receiver takes ( sometimes listed as the number of watts on the back of the receiver), you can figure the amps. P = IE, P (watts) = I (amps) X V ( volts). The I would rate the fuse at appx 2x higher that, for example for a 2 amp radio draw use a 4 amp fuse.
:Thankyou,.. but is this for the B+ /HT fuse that would be on the rectifier b+ leg and not the main fuse?
:Lou
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::Hello all.What is the best kind (fast/slow blow) and amp rating fuse to use for the B+ just in case of short etc.. (to protect rectifier /transformer etc..)....for 7- 9 tube Push/pull radio ..or how do you figure this out.Do you add the maximum current output of all the tubes ,including eye tube(6U5 etc.), (except the rectifier) for maximum current ???
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I can understand your thinking about a B+ fuse. However there are other things to consider. If the rectifier shorts out, this would be before the fuse. A short in the filament circuit would also be before the fuse. The transformer itself shorts out, this again before the fuse. It’s best to fuse the primary of the transformer. Any excess current draw anywhere should blow the fuse.

:I can understand your thinking about a B+ fuse. However there are other things to consider. If the rectifier shorts out, this would be before the fuse. A short in the filament circuit would also be before the fuse. The transformer itself shorts out, this again before the fuse. It’s best to fuse the primary of the transformer. Any excess current draw anywhere should blow the fuse.
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Thankyou Gentlemen

::I can understand your thinking about a B+ fuse. However there are other things to consider. If the rectifier shorts out, this would be before the fuse. A short in the filament circuit would also be before the fuse. The transformer itself shorts out, this again before the fuse. It’s best to fuse the primary of the transformer. Any excess current draw anywhere should blow the fuse.
::
:Thank you Gentlemen
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Here's an idea. Install a 1 or 2 amp slo-blo fuse in a power bar. It will then protect any radio you plug in to it. Use the switch on the power bar to reduce wear and tear on the radio switch. I leave most of my radios switched permanently on.