Analog controls for CDE and Hy-Gain rotators use a 25 volt pilot lamp
to illuminate the meter.
The bulbs don't last forever.
Most junkboxes are not stocked with 25 volt pilot lamps.
Faced with a dead 25 volt lamp, my first step was to use a 6.3 volt pilot light in series with a 100 ohm resistor.
The illumination was uneven (as it always was). LED replacements have been advertised in the back of ham magazines, but I didn't want to wait for a mail order to arrive, much less pay shipping and handling. I tried a few LEDs from my junkbox but the results were not satisfactory. I stopped by Surplus Gizmos on Cornelius Pass Road to look for high intensity LEDs. They had just what I wanted, a bar with 3 LEDs and a dropping resistor designed to run off 12 volts DC. They had a choice of colors, $1.85 cheap. For a little extra they will sell you a connector with red and black leads. A yellow LED bar is seen on the left. The picture below shows how you can use the lamp holder to hold the LED bar in place, in this instance a bluish-white / light purple that matches the meter on my MFJ 993B autotuner. I have bars in red, green, yellow, light yellow, and bluish white. Every now and then I change the color to get a refreshing new look.
Since writing this article I observed the blue/white bar losing output. In the meantime, Surplus Gizmos have added a bar with 5 instead of 3 LEDS for a more even output. I've come a long way from the single pilot lamp, haven't I?
After these pictures were taken, I decided to power the LED bar directly from the unregulated voltage through a 510 ohm dropping resistor donated by my junkbox.
Now I can leave the meter light on without burning up the lamp. Energy Star compliant.
When you stop by
Surplus Gizmos
Tell them Chuck WA7KGX sent you.
The board is normally attached to the meter's binding posts or on the chassis underside. I didn't like either mounting so I moved the small transformer next to the large transformer to make room for the board. A local Ace hardware provided longer versions of the nylon mounting bolts needed to get the board to clear parts underneath.
The board is not a beginner's Heathkit, but it did work the first time I powered it up. I got the RS232 version, which worked perfectly the first time I tried it. BTW, if you're looking for a USB to serial port cable, Frys sells a two port cable for $14 that seems to work fine with Windows 7 without installing any drivers. I would suggest extreme care locating the front panel LED holes if one desires the neatest appearance.
I replaced the red direction LEDS that came with the kit with blue ones.
In industrial controls, red means danger or failure, green means manual control,
and blue means automatic operation.
That said,
I used the red LED bar from Surplus Gizmos for the meter light.
The light is a much deeper red than appears in the picture.
The red light makes the meter harder to read than green or yellow,
but the resulting colors are dramatic.
The board is everything Idom Press says it is. The way the controls work with or without the RS232 option is cool.