[GreenKeys] Teletype REC 10 power supply available

[airrelic at juno.com]

Bill,   A year or two ago I had the same question about Selenium rectifiers bouncing around in my head and I started looking for why they go bad. Here is an excerpt from Army TM 11-473 dated 1944 on Central Office Maintenance.   “Rectifying Elements, sub-paragraph c. Aging. A rapid decrease in the amount of current which the disks will pass occurs during the first 3 months of service. This aging also takes place, but not as rapidly, if the rectifier is placed in storage and not used. The decrease in initial output does not generally amount to more than 25 percent of the rated output, and is provided for in the design of the rectifier by the addition of taps in the secondary winding of the transformer, to increase the current output as the deterioration increases. These transformer taps vary the ratio of turns in the secondary winding from those in the primary winding. Aging of the rectifier elements is brought about by internal changes and temperature. The speed with which aging occurs depends also upon the operating temperature; thus, the aging is more rapid when the rectifier operates under heavier current loads.”   In short, if it works at all, it won’t for long. The designers knew it wouldn’t last for long but Selenium was cheap and plentiful, and so was the labor to replace it regularly.   Kevin KD8QGX
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