[AMRadio] WE 303J


JAMES HANLON knjhanlon at msn.com
Thu Dec 17 13:30:13 EST 2009


Jack,

I don't have the info on the 303J you are after, but John, K2TQN, gave you good advice.  If you can find just one coil winding with your ohm meter, that's the one to work with.  You should be able to find the normally closed contacts, they will measure very close to zero ohms.  Monitor them while you ramp up voltage on the coil.  The nominal coil operating voltage will probably be either 24 or 48 volts.  If you get up to 48 volts and the contacts have not opened, reverse the polarity of the voltage and try again.  This relay will have a bias magnet, so you have to get the coil polarity right to make it operate.  The relay should operate on substantially less voltage than its nominal rated value.  It's operating time should be around 1 millisecond.  

Once the contacts have opened, you can use your ohm meter to find the "normally open" contact which at that point will be shorted to the swinger.  The swinger will be attached to one of the two pins you've been monitoring, and the normally open contact will show up on another pin.  

The mercury-wetted switch inside is probably a WE 226D, judging from the size of the relay can.  That switch is a single-pole, double throw switch that is of the "non-shorting" type.  The swinger will break free (open circuit) from the normally-closed contact before it makes to the normally-open contact on its operate cycle.  On its release cycle, it will similarly open up from the normally open contact before it makes to the normally closed contact.  The 226D switch is rated for a maximum of 3 amps DC current, and it should switch up to a 50 VA load.  Operated within its ratings, it should e good for more than a billion switcing cycles.  It will not "bounce" or "chatter" on either operate or release.  It should sustain more than 1000 Vac rms across its open contacts, although it shouldn't be used to switch that much voltage.  I've used a similar relay to switch B+ on the order of 300 volts at around 0.05 amps for keying purposes with no problem.  Insulation resistance of the open contact should be above 100 megohms.  Resistance of the closed contact should be below 50 milliohms.  

Once upon a time, back in the 70's, I was the supervisor of the Bell Labs group that was responsible for the design of WE mercury wetted relays, just in case you are wondering.

Hope this helps,

Jim, W8KGI


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