Any LC-40 Failures?

Ironflight · #1 06-24-2006, 10:05 PM

...Other than mine?

Just wondering if anyone has had any problems with the LC-40 lighting controller board. Mine is one of the older ones, no case - just a bare board that I mounted behind the panel. Today, while cruising out to the San Antonio area, I noticed that I had a popped circuit breaker - my internal lighting. That supplies power to the LC-40,and all the panel lights are powered off of that (except my flexible map lights, and of course, my EFIS and other internally lighted avionics). I don't believe in resetting non-essential breakers in the air, so when I landed, I looked at the Amp reading on my EFIS as I pushed in the breaker - amps climbed to 5 above steady state and the breaker blew. I'm convinced - got a problem!

I'm really not in a hurry to tear into the wiring, as all the internally lit stuff is more than I need if I were flying really late, but before I tear into it, I'm wondering if anyone else has experienced this board failing ?

Paul

kevinh · #2 06-24-2006, 10:20 PM

Quote:

Originally Posted by Ironflight

...Other than mine?

Just wondering if anyone has had any problems with the LC-40 lighting controller board. Mine is one of the older ones, no case - just a bare board that I mounted behind the panel. Today, while cruising out to the San Antonio area, I noticed that I had a popped circuit breaker

Hi Paul,

You might try checking the back of the board - perhaps a sliver of 2024 or somesuch has landed between two traces. What regulator is on the board? I'm guessing a LM317.

Walt · #3 06-25-2006, 01:22 PM

I don't recall the model off hand but mine has the heat sink on it and I recieved 2 bad ones new from BC, finally just repaired the second one myself. I forget exactly what it was but it was either the insulating washers or solder flash on the board that had the case of the large TO3 transitor shorted to ground. The case is the output so if it shorts to ground the current will trip the fuse or breaker. Hook an ohm meter between the case of the transisitor and ground to see what you get, if it's zero then look for the short. Of course if you have an older unit an it has been working fine for years then it's likely the output transistor is shorted (common failure if it's been running for a long time).

Ironflight · #4 06-25-2006, 03:04 PM

Thanks for the feedback guys. I checked over my notes and unless I have a wire short somewhere, the problem almost has to be in the dimmer board. In actuality, it does have a lot fo runtime, becasue the airplane was alive through ground power supplies in the shop for many, many hours before it was finished - and the dimmer circuit was powered all tha time. I'm building a little fault tree of things to check when I get a cool day and want to pull the panel, and I bet it will be the output transistor....

Paul

Walt · #5 06-25-2006, 06:38 PM

If your does not have the hint sink then you need to install one, even thought the TO3 case of the output seems large it cannot disipate heat very well without a heatsink.
Walt

vic syracuse · #6 06-26-2006, 06:28 AM

I've had 2 failures of these units now, and I have not reinstalled a 3rd one. I rewired with heavier duty dimmer circuits, even though the circuit totals were well below rated capacity. They do not impress me as being very reliable.

Vic

kevinh · #7 06-26-2006, 09:43 AM

Quote:

Originally Posted by vic syracuse

I've had 2 failures of these units now, and I have not reinstalled a 3rd one. I rewired with heavier duty dimmer circuits, even though the circuit totals were well below rated capacity. They do not impress me as being very reliable.

Wow - I don't know what they used on this LC-40, but I wired my own by using a linear voltage regulator. I was only powering a few lights so I needed less than 1.5 amps of variable brightness.

It is super easy:

Download this datasheet. See page 7 of the datasheet for a sample schematic
Install the LM317 (available from Digikey, Fry's, possibly even radio shack)
Install R1, R2 and C1 - a total of only four components, you don't even need a circuit board. The value of C1 is not critical, it's just for noise suppression.

Should cost less than $5 and take less than an hour to build.

Update: Just checked the web, radio shack has 'em

vic syracuse · #8 06-26-2006, 03:55 PM

You're right, and I had done this on my previous 5 airplanes. I thought I would be quicker and use the LC-40 on this one, and I have regretted it ever since.

Vic

Davepar · #9 06-26-2006, 04:04 PM

Kevin,

Can those be used on LED lights as well?

kevinh · #10 06-26-2006, 04:07 PM

Quote:

Originally Posted by Davepar

Can those be used on LED lights as well?

yes - if they are already mean't to hook to 12V. In that case the LED has a resistor in series so that you can change the brightness with this LM317 as you wish.

If you want to use a 'raw' LED with this regulator (or any voltage source really), you'll need to ensure that the LED is connected to the supply through a resistor. (A cheezy way of varying the current through the LED based on voltage)

You can use the information on your particular LED with a calculator like the following to pick out the appropriate resistor: http://ourworld.compuserve.com/homep...Bowden/led.htm .