Author Topic: adding fuse to tube radios  (Read 71 times)

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Offline kinkydoints

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adding fuse to tube radios
« on: January 28, 2019, 09:38:57 AM »
in my rebuild of a hallicrafters s120 I would like to add a slow blow fuse to the " hot" side of the main ac line in. what are the factors I need to think about in choosing the correct amp fuse? Should this fuse be the first thing the line in powers up on it's way through the unit.
KN4SNM

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Re: adding fuse to tube radios
« Reply #1 on: January 30, 2019, 08:22:28 PM »
Good question. If you pull of the specs you can maximum current draw.
The filaments will draw about 150ma when first powered up, and total will be around 30 watts of power. this is near 4 amps. So a 5 amp fuse should be ok.  I like the fuse before the switch. Remember switches and short also.
Buddy kc4umo

Offline kinkydoints

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Re: adding fuse to tube radios
« Reply #2 on: January 31, 2019, 01:07:50 PM »
without doing more investigating , seen a video that stated the unit runs at about 30 watts. in my study guide for my tech ticket , going sat. for exam here in KY. I noticed a  ...P-I-E ... circle , to help in calculating the different answers , were P is power in watts, E = voltage  dividing to get I = amperes .  called it 130 VAC / 30 =4.34 or so... and ya I did work out that same rated fuse. I will post some pics in the other forum to update this S120. thanks 
KN4SNM

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Re: adding fuse to tube radios
« Reply #3 on: January 31, 2019, 10:45:41 PM »
If it were me I would put the fuse first thing.  Looks like you have already worked out the rating. :)
Michael, KE4EST