[Hallicrafters] S-40A question and info

[Edward B Richards]

Hi Scott;

It is a good idea to add a fuse to the old radios that don't have one. I
do it too. It is also a good idea to change to a 3-wire power cord and
plug for any equipment with a metal housing. May save your life.

A fuse is usually rated for 1-1/2 times the rated current draw. The S-40B
is rated for 75 watts. I imagine the S-40A is similar. At 122 VAC*, this
would be about .6 amperes. A 1 Amp fuse would be appropriate. Put it in
line with the switch. Make certain this wire goes to the hot side of the
line. i,e. the narrow pin or black wire.

A 3-wire cord and plug should be connected so the black (hot) wire goes
to the fuse, then the switch. The neutral (white) wire goes to the other
side of the power transformer. The safety ground (green) wire goes to the
metal cabinet. 

*I don't recommend running these old boat anchors directly off the 122
VAC line, as that is 5-10 volts higher than the radio was designed for.
Use a voltage reducer to protect your power transformer. See BAMA home
page about 1/2 way down for instructions for making or buying a voltage
reducer, by K6UUZ (me). Good luck/

73, Ed Richards K6UUZ



Hello, my name is Scott. I'm working on restoring an S-40A. I have a 
question and some info on my restoration.

Question: I want to add a fuse to the power cord inside the unit. I have
an 
old style bakelite and copper fuse holder that will look nice inside but 
what amperage do I use (2 amp?) and which side of the transformer do I
put 
the fuse on? The heavy black line coming out of the transformer or the 
smaller one running to the power switch?

I figure adding a fuse is good insurance to at least have some form of
line 
protection. I have much common sense in working on circuits and
electrical 
stuff but I lack the in-depth technical skills. I can solder and test and

clean and everything else no problem but when it comes to figuring
technical 
electrical equations out: forget it. So I thought I would ask one of you
for 
help.