sticky relay

[KB5MD]

I have a large solenoid type relay  in my transmitter that is used to switch the plate transformer on when keying.  Is there a way to prevent the contacts from sticking? I have replaced the unit before but I would rather find a way to prevent the contacts from sticking.  It is switching 240 volts AC  on/off.

[WQ9E]

Check first for a mechanical issue (binding, dirt in mechanism, etc.).  Then add properly sized inrush limiters to protect contacts on make and arc suppressors (resistor and capacitor in series across contacts) to help protect the contacts on break.  You can find advice on the resistor and capacitor value in the older Handbooks and Mouser sells the resistor/capacitor combined as a unit.

Or do like I did with my Johnson Desk and replace the mechanical contactor with a pair of solid state relays.  If you are not using inrush limiters they are cheap (around a couple of bucks) and should be added no matter which switching solution you choose.

Rodger WQ9E

[WA1GFZ]

I would use step start with snubbers across the contacts.