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gemeinsch: DAF1011 (DAF 1011); What is "Pruefspannung"?

Martin Renz Ernst Erb Vincent de Franco Martin Bösch Mark Hippenstiel Bernhard Nagel Dietmar Rudolph Otmar Jung Heribert Jung Eilert Menke 
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Forum » Radios and other type of sets (Physics) etc. » MODELS DISPLAYED » gemeinsch: DAF1011 (DAF 1011); What is "Pruefspannung"?
Michele Denber
Michele Denber
USA  Articles: 129
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30.Aug.09 19:24

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I'm selecting new capacitors to replace the block electrolytics in my DAF.  One of the schematics I have lists two separate voltage ratings for them: Arbeitspannung (which I assume means "working voltage") and "Pruefspannung" which is much higher.  For example, the 0.5 uF preamp coupling capacitor no. 97 on the AC2 plate has a listed working voltage of 400 v. but a Pruefspannung of 1500 v.!  I can't even find capacitors rated that high.  What does this number mean?  I have a 0.47 uF capacitor rated 630 v.  Is there some reason I should not use that?  Thanks!

Torbjörn Forsman
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30.Aug.09 21:58

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"Pruefspannung" means test voltage. For paper capacitors of old days, the factory test was always performed at a much higher voltage than the capacitor's rated operating voltage. At least in Europe, it was common practice to mark the capacitors with the test voltage and then it was up to the radio design engineer to apply a suitable de-rating. When using modern polyester or polypropylene capacitors, there is no need for de-rating, so 400 V or 630 V capacitors can be used in all positions in old radios. The only exception is RFI filtering capacitors across the mains input or across the anode voltage winding of the mains transformer, those should be replaced by capacitors designed for such use. Such capacitors are marked X1 or X2 and have a lot of approval marks from various safety authorities. Capacitors for connection from either side of the mains to ground should be marked Y1 or Y2, this is also valid for, for instance, the protection capacitors for the antenna and ground terminals of transformerless AC/DC sets.