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September 13th 03, 03:43 AM
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Dick Carroll; wrote:
W7TI wrote: On 3 Sep 2003 10:13:00 -0700, (Mike Silva) wrote: Another question resulting from too much time on my hands. Why do we have rectifier diodes (e.g. 1N4xxx, 1N54xx) with different voltage ratings? Other than the voltage rating I don't see any differences on the data sheets I've looked at. Why not just make and use 1kv diodes alone? 73, Mike, KK6GM __________________________________________________ _______ $$$ -- Bill, W7TI Yep. And I'd wager if one did breakdown tests on a variety of diodes many would show the same specs regardless of their different markings. Another pet peeve- Several times I've seen failure of low voltage capacitors which were run too close to their ratings for comfort, IMO. Like 16 vdc rated on a 13.8 DC line in mobile gear. Spikes are sure to take 'em out eventually, it would seem. Why designers do that I've never understood, and I never replace them as rated, but use 25 or 30 volt caps. Never had a problem from doing that, and no repeats. I remember years ago troubleshooting a dead board in an Atlas 210 transciever that had a shorted - leaky 16 volt rated electrolytic across a 13.8 dc line on the board. But it still had enough internal resistance that it didn't smoke anything, just killed the operation of the board. I cussed the (unknown) designer of that thing for awhile! /:-D)) Dick, Electrolytics should be run near their rated voltage to "form" properly. The spikes should be taken out by a parallel 100nF cap, or clipped by a zener. Rob |
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