Quote:
Originally Posted by Kamakiri
This is the relay that was retrofitted under the chassis. Look like it should work?
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The P&B relay is within specs on amperage, under specs on voltage, but probably is OK. (Switching 440 + DC with a 120V RMS AC rating.)
Apparently Du Mont did not publish the pull-in current requirement
and that makes it impossible to answer without a test.
What should be a safe way to check the relay is to remove both 5U4's but leave the two 6X4 bias rectifiers in. Unsolder both switched leads. * (The lead going to the 5U4 will have 440 AC on it, so cap it.)
Put a battery and same voltage test lamp in a loop circuit with the switched relay contacts. Power the set up, still with 5U4's out, and remove and replace the 6AL5 power delay tube. The relay should click with each operation, possibly with a slight delay. Test lamp should be on with tube in, and out with tube out.
If relay clicks, but does not light the lamp, the relay is bad. If relay does not click, the trouble probably is in the switching circuit, but there is also a slight chance it could be a bad relay, or the relay coil pull-in rating is incorrect.
With that said, I've never done a relay test on a Du Mont, but have used similar methods on other industrial equipment when I did not have component information or a spare relay. If anyone sees anything I just wrote potentially harming the set, please holler now!
Jas.
* Oops! Clearly an oversight above, hope there are no more.
Before someone points it out, with the 5U4's removed, the only voltage on the socket filament pins is 5 V AC since the 440 AC is on the plates. I would still cap the hot wire before running the test.