the 9004, a twofer

 I used to live/work in Illinois.  My last job was in Manteno, a town about 58 highway miles south of Northlake, where I lived in Cook county.  This meant a lot of headlight driving.  I was constantly changing the headlights on the Taurus, the 9004 halogen:

Driving in the metro Chicago area there was little use of the hi-beams so when I took the 9004 lamps out I kept them because one of the filaments was usually still fine.  

What can be done with old 9004 headlamps ?  One thing is they make a good load for testing power supplies.  As can be seen here in my lab notebook, the 9004 provided a load of 5.2A when testing the rectifier portion of my K2 power supply:

 

BTW, the ARRL uses lamps as loads, although in this case Bob, WB1GCM, is testing AC genertors with 120V incandescent lamps but it's the same idea: https://youtu.be/rOH7Ze7wreQ?t=214  And here is a screen cap from another ARRL video (of the Ameritron ALS1306 Amplifier) that shows a bank of incandescent lamps that was used in inverter testing per an email from WB1GCM:

And of course in the 20th century it was common for Novices to use an incandescent lamp as a dummy load for their tube transmitters, I even made a contact on mine with a fellow down the street.

So what is the twofer ?  The 9004 is mounted in a plastic lens bolted to the car unlike the old sealed beam headlights which included a reflector and lens.  So the 9004 has a black or red rubber O-ring to seal the assembly from the elements.  I took the O-rings off the 9004 and found that they fit nicely on the tuning knob of my Elecraft K2 which makes changing frequency a little nicer on the fingers:

Got to love the twofers in life !  Maybe if use as a headlight is included, it was a threefer ?

Best Regards,

Chuck, WB9KZY
http://wb9kzy.com/ham.htm