Selenium rectifier testing ?
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From: N Cook on 20 Nov 2007 10:08 Tim Schwartz <timhhk(a)verizon.net> wrote in message news:4742E41C.3010304(a)verizon.net... > N Cook wrote: > > In a valve Dansette Bermuda of early 60s > > Been in a loft for years. > > The mains wiring is perished and other wiring looks dodgy so testing some > > things cold first. > > Using 9V battery and 300 ohm dropper shows near enough 9V over the > > rectifier, how high V do you have to go with a good one to check it ? > > Are there safety grounds anyway for changing to a 1N4007 or so ? > > Single element rectifier > > Siemens lazy S logo > > Made in Germany > > 2250c50 > > Kc 0.6e 11/16 > > > > > > -- > > Diverse Devices, Southampton, England > > electronic hints and repair briefs , schematics/manuals list on > > http://home.graffiti.net/diverse:graffiti.net/ > > > > > > > Nigel, > > Take another look at the number. Might it be "B250C50"? Many European > rectifiers used to give you the voltage (B, in this case 250 volts) and > current rating (C, in this case 50mA) of the device. > > I agree with the other posters that you can replace the selenium with a > silicon diode, but may need to ad a dropping resistor as the B+ may be > higher because of less loss in the rectifier. I usually bring the item > up slowly on a variac and make sure that I don't exceed the voltage > of the filter caps. Better still if you have a factory diagram telling > you what the B+ is supposed to be. Then you can choose an appropriate > resistor, and you might need quite a few watts worth too. > > Unfortunately, I can't suggest how you might test the selenium. > > Regards, > Tim Schwartz > Bristol Electronics I have a1979 Siemens databook and E250C50 were still listed, rating only 200V, 20mA I removed and tried on a bench supply thru 330 ohms. Took to 25V and read over the rectifier 25V, powered either way So will replace with silicon -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/
From: James Sweet on 20 Nov 2007 13:10 >> > Nigel, > > Take another look at the number. Might it be "B250C50"? Many European > rectifiers used to give you the voltage (B, in this case 250 volts) and > current rating (C, in this case 50mA) of the device. > > I agree with the other posters that you can replace the selenium with a > silicon diode, but may need to ad a dropping resistor as the B+ may be > higher because of less loss in the rectifier. I usually bring the item up > slowly on a variac and make sure that I don't exceed the voltage > of the filter caps. Better still if you have a factory diagram telling you > what the B+ is supposed to be. Then you can choose an appropriate > resistor, and you might need quite a few watts worth too. > > Unfortunately, I can't suggest how you might test the selenium. > There isn't realy any reason to test them. Given how nasty it is when they fail, and how likely that is to occur, I replace them any time I encounter them.
From: Reinhard Zwirner on 21 Nov 2007 16:10 Tim Schwartz schrieb: > > N Cook wrote: > > In a valve Dansette Bermuda of early 60s > > Been in a loft for years. > > The mains wiring is perished and other wiring looks dodgy so testing some > > things cold first. > > Using 9V battery and 300 ohm dropper shows near enough 9V over the > > rectifier, how high V do you have to go with a good one to check it ? > > Are there safety grounds anyway for changing to a 1N4007 or so ? > > Single element rectifier > > Siemens lazy S logo > > Made in Germany > > 2250c50 > > Kc 0.6e 11/16 .... > Nigel, > > Take another look at the number. Might it be "B250C50"? "B" stands for _B_r�cken-Gleichrichter (bridge rectifier), whereas "E" stands for _E_inweg-Gleichrichter (half-wave rectifier). 250: rated voltage = 250 V "C" stands for _c_apacitive load. 50: rated current with capative load = 50 mA HTH Reinhard
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