Would like to add an in-line fuse to my 38-4. The switched leg of the power cord travels thru a .015 bakelite cap on its way to the on off switch. Would it be ok to attach the fuse between the bakelite cap and the switch or does it need to be inline before the cap. Thanks, Gary
When I add a fuse to my restored radios, I always put it before any line capacitors or the on/off switch. If anything fails in the radio the fuse will blow.
I agree with mandh.
The line supply is capable of near infinite amounts of current.
If anything shorts before the fuse, the fuse can't offer protection.
If the line condenser is ahead of the power switch I would seriously consider rewiring it so it is on the other side of the switch, I'm surprised that Philco would design a set this way, that's more of a Zenith trick which I hate. You could add a fuse on the primary side, on either leg or both, or add one on the filament/cathode leg of the rectifier where it heads to the filter condensers.
Best Regards
Arran
I've been thinking about fuses lately and I'm wondering if you would use a slow blow fuse and how you would go about sizing the fuse properly.
I use a 2A fast blow fuse on both the 5 and 6 tube receivers I have restored. I want to make sure that the fuse blows before anything else in these old radios and the surge current is not that high, so the fast blow fuse is OK.
I'm a fast blow man too! Usually 1.5A for 5-6 toobers. In spite of what is said about nuisance blowing I've never had it happen. A decent fault should take out a 1.5 or 2 amp fast blow just as fast.
Some slow blow fuses will allow up to 400% for a second or two? and 200% for even longer.
I'd have to agree with fast blow for all tube applications. They are easy to come by too. 1 amp is ususally sufficient for small AC-DC sets. It's not a bad idea to put another fuse in the B+ circuit. This can be a 1/2 amp or smaller depending on the draw. Beats scouring Epay for yet another obscure tube.