Lawdog14 with the sticky relay switching over to or from battery backup. This is going to sound crazy but you should try it before you laugh. I solved many a relay problem by sticking a thin piece of paper between the soft iron core of the coil and the clapper of the relay. Sometimes the soft iron core becomes slightly magnetized and won't pull in or release the clapper properly. A thin piece of paper covering the iron core of the coil will change the magnetic flux and allow the relay to operate as it should. I repaired about 500 Apple Laserwriter II laser printers with this method, by inserting an Avery sticky label attached to the soft iron coil core, The printers were intermittently indexing on the wrong line when printing. Bad news when printing on forms. Second thing to try is to make sure a fine piece of metal such as a file shaving is not magnetized on the soft iron core When the coil is energized the metal flake changes position and prevents proper control of the moveable clapper plate. Please no boos from the BMOC.
Gary K2UQ
If you have a slightly magnetized relay core you need to also
reverse the connections to the relay coil. The magnetic flux
that is magnetizing the core is generated by the current in
the winding and exchanging the wires reverses the current
and the flux.
This is why some relay coils have push-on tab connectors...
makes it easy to exchange the wires periodically...
Learned that trick from Martin WA6TIC while working on
his crossbar PBX back in the late 70s... 21 incoming and
outgoing trunks and 150 extensions, and ALL RELAYS...
Mike WA6ILQ
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