Fox's Mercantile wrote:


How do you test a Selenium Rectifier?

Yes, I am aware that they should be replaced, but on preliminary tests
of this 1956 Zenith tube AM-FM Radio, I want to know if it's working. My
digital multimeter shows 1meg in one direction, 2.5 meg the other way.
NOT DISCONNECTED FROM THE CIRCUIT. To me, that seems bad, but I have not
worked with one of these in many years, and never had to replace one in
the old days. My meter was climbing, probably from the filter caps.
during this test.



A DMM won't read correctly. No enough voltage compliance on the current
source to read ohms correctly.


** Most DMMs have separate ohms and diode tests ranges, the ohms ranges
are for " in circuit" resistor testing and will not make a good Silicon or Selenium diode conduct.


Just replace it with a 1N4007 diode and about 100 ohms series resistor.


** Really ? Only the wimpiest rectifier has 100 ohms series resistance, like a Germanium detector diode.

The OP's Selenium rectifier powers an AM / FM radio,( minus less the tube filaments ) so ought to be good to half an amp - so maybe try 22 ohms @ 5watt.


..... Phil