Thank you very much for your detailed response. Answers to your
questions/comments, below:
wrote in message
...
In rec.aviation.owning DL wrote:
Very long shot, I know, but - does anyone have any schematic or any
documentation whatsoever on a pilot controller runway light controller,
Model BX-2, made by Subil Enterprises, Inc., Des Moine, IA 50317?

Does it have its own receiver or does it plug into the audio output of
another receiver?

It has its own receiver, power supply, logic to respond to unicom clicks to
turn lights on and off and power relay for runway lights.


Problem is very low sensitivity.

How's the antenna, coax to the antenna, and any other connecting cables?
These crap out with surprising regularity. (This applies even if the
light controller is plugged into another radio.) If the antenna is also
used for transmitting, and you can get an SWR meter, you might check
the SWR to see if it's way high.

Have checked antenna coax and connections and found no problems, including
continuity/shorts check of antenna (very short cable).

If the controller plugs into the output of another receiver, have you
tried the controller with a different receiver?

Inside the box, even without a schematic, you can check a few things.
Some you can do with a multimeter and some need an oscilloscope.

Power supply up to snuff - steady, ripple-free voltages? Depending on
the voltages, you might be able to temporarily substitute a battery,
which is almost guaranteed to give you "clean" power. In something of
that age, the filter capacitors on the power supply are likely suspects.

Power supply checked with voltmeter and scope; seems clean, may try with
battery or alternate power supply.

Get a strong light and a magnifying glass and check all the solder
joints, especially ones to massive components and off-board wires.
Especially check the input jack (antenna or audio) - these are often
subject to mechanical damage from the cables that are plugged into them.

Check the first few components immediately after the input jack (antenna
or audio). These bear the electrical brunt of goofy signals coming in
the input. See if resistors and capacitors are open, shorted, or have
changed value dramatically. See if inductors are open. You might have
to unsolder one end of the component involved for a good test.

Will do. First section is FET RF amp. Will look closely in that section

If it has its own receiver, and is crystal-controlled (you can't program
in the frequency), check the crystal for oscillation at the proper
frequency and/or swap in another crystal. This may cost you a few bucks
and some time for the new crystal, so it's not first on the list.

Is crystal controlled. Have tried frequencies above and below the 122.9
spec. to see if I could detect a higher sensitivity off frequency. So far,
no definitive results. It works, but handheld needs to be close to the
antenna.

Resist the temptation to adjust any internal trimpots or coils at first.
If you can't resist, mark them well so you can put them back where they
were when the adjustment doesn't help. "I will remember where it was"
is not a mark.

Have successfully resisted that temptation thus far. Good advice.

Google says this guy
http://fmi.typepad.com/lwyp/2006/10/..._lighting.html
was looking for information on a similar unit; you might contact him and
see if he found anything.

Had seen that too. Good advice to try to contact him. Is a different unit.

Hamtronics sells a solution. Much more capable board, $229, plus wall wart
PS, plus solid state power relay. Such a full solution (with my packaging)
could be had for under $300 - not enormous when absorbed by a number of
folks. But I am stubborn and would like to find the culprit in this box, as
the fix, if found will be less than $5 including shipping and sales tax,
from Mouser. And I'll chalk my time off to a "learning experience" . . . .
up to a point, at least!

Disclaimer: This is based on experience with electronic equipment in
non-aviation applications. I am not an avionics technician. I don't
have an A&P; I don't even have a TG&Y. Your mileage may vary.

Matt Roberds

Thank you again. Obviously you've had some real experience with
troubleshooting. The beauty of this situation is that you don't have to be
an A&P, IA, FCC, anything that I know of. It's at a private field. No one
is guaranteed that it works every night. But it has for years, until now.

DL