This provides two functions - isolation from the AC source, and reduction of the line voltage via the taps. The local line voltage is 122 vac. This is within the Hallicrafters stated operating range of 105 - 125 vac. Some comments from other restorers mentioned that the power transformer in the radio runs hot with the higher voltage. Waste heat is not kind to any electronics, and since this features 50+ year old electrical bits, I want to give it a break. The radio 'starts up' around 90 vac, runs perfectly at this lower range, so I chose the 105 vac taps on the isolation transformer. The assembly is much smaller than the Powerstat (which does not provide line voltage isolation).
Isolation/voltage reduction transformer.
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Initially, I was going to put it inside an enclosure. Since it was going to generate heat, I tried to find a ventilated box. To limit size, I decided that the transformer would be fine outside the box, so to speak...
The chassis is also made by Hammond, about 6 by 4 by 2 inches. Since I do not have the proper metal working tools to cut a neat hole for the line output, I simply used the mouse-tail method. A power switch was added, as there is no need to consume electricity when the Halli is powered off. Total current draw with the radio powered on is .58 amps, with an input line voltage of 121 vac and output of 102 vac.
Under the hood...
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I wanted to preserve the ability to change the line voltage, so all of the taps are available on this connector.
Standoff detail
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For easiest access to the connections, I mounted the barrier strip on 1/2 inch nylon standoffs. While scrounging through the materials at the local hardware store, I found nylon standoffs that fit into the mounting holes of the 10 position Cinch barrier strip. This illustration is with a different barrier and standoffs that I did not use - in the finished box the standoffs fit perfectly in the mounting holes, providing excellent stability.
The Cinch 8-position barrier picture above will be used for an impedance matching enclosure for my older battery radios.
I will soon add a line fuse for this box - just waiting on a part. The radio runs well on the reduced voltage, perhaps lasting a little bit longer.
Next - I'll scan the entire manual in PDF format for amusement.
