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.