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The Wireless Connection
Your
Test Bench: Variable by Peter J. Bertini |
Photo B. This is the ceramic-cased wax-paper capacitor responsible for the unit’s shifting output voltages. |
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Like most hobbyists, I have a “wish list.” There are items I covet more than others, and there are those things I can live without, but would buy if the price were right. So it was when I found a Hickok variable DC power supply being offered on a well-known Internet auction site.
The unit’s specs were strikingly similar to
the Heathkit IP-27 bench supply: 0 to 400 VDC at 100 mA continuous, 0 to
-100 volts at 1 mA for the C bias supply, and a 12-VAC center-tapped
output with a generous four-amp rating. The PS-501A is an odd duck. I couldn’t find out much about it, and the “Hickok Teaching Systems, Inc.” silk-screened on the front panel led me to believe the unit was produced for the educational field: colleges, technical schools, etc. Perhaps the limited market is the reason so few are evident today. An Internet newsgroup plea for help garnered a well-worn and much recopied manual for the Stark PS-501A power supply, Stark being the Canadian manufacturing facility for Hickok. Indeed, the gentleman who provided the manual owned the same unit, but his bore the Stark brand name. The tubes in my unit were branded with either Stark or Hickok labels, so the connection appears correct. The manual copy was very poor and faded and appeared to be a third or fourth generation hand-me-down made from of the original manual. I took the liberty to redraw the schematic as shown in Figure 1. I’m pretty sure it’s correct, but I can’t promise complete accuracy due to the poor quality of the print I was given. I suspect other supplies, by other manufacturers, will bear a striking resemblance to the Hickok circuit. |
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