> On Jul 12, 2019, at 8:50 AM, Bill Notfaded <[email protected]> wrote: > > Phil is right. > > This true about 400 Hz... you know the reason that frequency is used in > aircraft? For those that don't know... it doesn't require transformers or > motors that are as large for higher frequency so thus it weighs less.
I don't know about frequency or if it was even AC but trains used a lower voltage, something like 60V. I have a passenger car light bulb that I can't get to it right now to check. The bulb is screwed into a socket with a large spring between it and a male Edison screw at the end. I guess it absorbed vibrations and kept the filaments from breaking more often. Cable TV line amplifiers used 30V or 60V, 60Hz square wave AC back in the '80s when I worked at ComSonics. I don't know if that's changed since then or not but the power supplies had special transformers designed to handle square wave AC. The reason they didn't use sine wave was because the battery backup power supplies could only produce square. There was one line extender made by a well-known company that had an alarming tendency to fry its (expensive) transformer. The cause was simple. Some genius put the fuse between the bridge rectifier and the filter caps, not between the transformer and the diodes. A few surges and zap, a diode shorted out and overheated the transformer until a winding melted open. If the customer paid extra for a one or two year warranty we put surge protectors on them and that solved the problem. We hardly ever had to repair an amp after we put one in it. After a few months an engineer from the well-konwn company called us to ask what the hell we were doing to their product to keep it from burning up. True story, can't make stuff like this up. In 1983 the need for surge protection was not well understood even with commercial electronics. Lightening arrestors, yes (we replaced a lot of them). In fact, the surge protectors we used were designed by the owner of the company and custom manufactured in-house. There was one ancient power supply (no PC board, just point-to-point wiring) that had a failure mode where it kicked back a voltage so high the arrestor on the input would ionize and light up. Terry Bowman, KA4HJH "The Mac Doctor" Male voice: "That accident over in Red Sector L destroyed another 63 personnel, giving them a total of 242 lost to our 195. Keep up the good work and prevent accidents. This shift is concluded."—THX 1138 -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/B6A1C63B-4369-4227-A805-ABFE16C28547%40gmail.com. For more options, visit https://groups.google.com/d/optout.
