grundig: 80U (80 U); Rectifier / Gleichrichter |
Joe Sousa
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What kind of solid state rectifier is in the Grundig 80U? The part number in the original Grundig schematic is E 250 C50N. The schematic shows a single diode. The shape is unusual: The model 88 has a full wave bridge rectifier type B250C75. The Sams schematic classifies the bridge as Selenium: The Grundig model 85 has a single diode rectifier of the type E 250 C85: If these are all selenium rectifiers, are they more reliable than the kind where the diode plates are exposed? Regards, -Joe Dieser Beitrag wurde am 05.Jun.09 18:46 von Joe Sousa editiert. |
Georg Beckmann
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Hi Joe, this is a selenium rectifier. E stands for 'Einweg' what means one way or single diode. Opposite you find B for Brücke what means bridge. Georg Dieser Beitrag wurde am 05.Jun.09 20:13 von Georg Beckmann editiert. |
Emilio Ciardiello
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Dear Joe, |
Hans M. Knoll
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Hello Friends. For technical Information, see here
regards Hans Anlagen:
Dieser Beitrag wurde am 07.Jun.09 18:43 von Hans M. Knoll editiert. |
Emilio Ciardiello
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The documentation on AEG rectifiers kindly loaded by Mr. Knoll gives an idea of their size. By the way, the based models may be considered forerunners of the silicon solid-state tube replacements from the late ‘950s. Regards, Emilio |
Joe Sousa
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Dear Hans and Emilio, Thank you for the excellent information. I also followed the excellent article threads that Hans shared. This will be useful as I attempt a restoration on Grundig 1045W, which has a full wave bridge. I am currently on vacation in the Azores. Last year I offered a neighbor in the Azores to restore his 1045w. I have a couple of pictures that I could contribute to the model, but the radio is still quite dirty. One point stands out on Emilio's recommendations, and that is that a selenium rectifier may need some reforming if it has not been used for a long time. This long term degradation suggests to me that the rectifier is always in some state of flux. Perhaps occasional use keeps it in good shape, as is the case with electrolytic caps. Another point is that many natural processes, that involve particle flows, tend to double every 10oC. This brings forth the importance of keeping a low temperature to stabilize the chemistry of the selenium rectifier. I have replaced only two selenium rectifiers in several Grundig AM-FM three tube radios that I own, and I use them regularly, without any trouble. So reliability seems good, but don't exceed the limits. One of the radios that I replaced the selenium rectifier was the Grundig 80. The other rectifier was perhaps in a model 85 with the thin chassis mounted kind shown above. Regards, -Joe |