[Hallicrafters] s48A with my safety mod

[Kirk Z Bailey]

All the parts arrived at last, and I sat down tonight to do it.

First, replace all the electrolytics. My, how they have shrunk over the 
years... The 22uF 50V unit for the PA cathode is like one of the 
RESISTORS in this thing. Pretty straightforward job thus far.

Now, gritting my teeth, GUT the old dangerous basic power loop and 
change it to something man rated. This goes slow as I puzzle out how 
they actually built it, as opposed to the theoretical circuit diagram. 
Turns out they were using a lot of unused socket pins as tie points, 
which creates confusion.

Then, smoke test #1, plug it in. OK, nothing. it passed stage one. Now 
stage 2, turn it on.

Cringing, I turn theknob with a terrifying -CLICK-.

No smoke, no pops, no BANG!, no sizzle, the lights stay on, and in 
seconds it is QUIETLY SOFTLY humming, and playing local stations on a 2 
foot wire for an antenna.


WOOHOO!

And now it is safe, with a decent power cord with polarized plug, and a 
PERMENANTLY GROUNDED chassis. It is speculated the makers of AC/DC sets 
would put the switch on the ground side of the circuit to minimize 
capacity coupling of hum to the volume control right next to it. Well, 
for the reward of staying alive, I will accept a little minor hum. Until 
i figure out a way to introduce counter hum to kill it... or change it 
to use one of the p[anel sqwitches to control power? NAH, that's not 
restoration.

It works, it is safe. It has a power cord THAT IS PERIOD, a 2 wire 
polarized plug with brown rubber insulation. Now to go polish up the 
instructions on the website.

IT turns out that in the S38A there is a single bare wire jumper at the 
switch to cut that goes down to ground, a black wire there to leave in 
place, and move AT THE OTHER END at the rectifier to pin 2 where the 
heater, the bulb's white wire, and the resistor shunting the lamp all 
come together, and move said black wire to THAT pin. Obviously the stubs 
of the old power cord are removed and given a decent burial along with 
the old capacitors removed.

There are a number of convenient places to ground the neutral wire to 
chassis, I picked on on a 2 terminal strip that has a wire come to it 
from one of the front panel switches.

Tommorow, into the case, and mount new grommets in it, and set it up 
here in the home office/radio shack/COMP SCI LAB, and carry the S38 
original in the kitchen for it's dose of surgery.

-- 
end
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        - Kirk Bailey

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