25-Volt Carriage Lamp Replacement

This Instructable will show you an alternate method for lighting in an outdoor 25-volt AC lamp system. It appears these were popular around the late 1980's.

They went out of style, though the systems are still intact, and the special lamps are no longer available. Anywhere. If you screw an ordinary 120-volt incandescent lamp into the socket, it will trash the transformer that powers it. Immediately.

My method requires some simple soldering, some wire, a few cheap LED's from eBay, cheap bridge rectifiers from eBay, some "heatsink plaster" from eBay, some time, some glue, a couple of light socket and extension cord plug adapters from Home Depot/Lowe's/etc. and that's about it.

Some LED's will last forever, some will fail in a year or two -- it's really luck of the draw unless you want to spend some serious money for the LED's.

If I find an LED that's failed, I just tear it off and replace just that part. That's quicker than starting a new assembly from scratch. It's usually pretty obvious which piece has failed.

Our subdivision is about 30 years old. Shortly after being built, we added 7-foot tall gas lit carriage lamps to the front yards with an address sign. A few years later they were converted to 25 volts electricity. I don't know where the address signs came in.

At that time, you could buy 25-volt incandescent lamps (that were much brighter than the 12-volt versions) that looked just like ordinary household lamps.

Also, installing a pair of 12-volt automobile tail light lamps in series meant they could light up a wide address marker box (12V + 12V = 24Volts).

Everything was fine until landscapers chose to use 12-volt lamps everywhere and 25-volt systems went the way of the dodo. They stopped making the 25-volt lamps, and once they burned out like any ordinary light bulb, there were no replacements.

We moved into the neighborhood a few years back, and I quickly discovered most of the lamps were burned out. Seeing this as a safety issue (no streetlights, so addresses were hard to read) I took on the task of finding a solution.

Long story short, I buy 12-volt LED packages on eBay, hook two of them in series and power them through a bridge rectifier, use a heat-sink hard-drying product to mount the LED's to a heat sink, then wire them in series to create a 24/25-volt package. While technically the LED's should light without the bridge rectifier (AC supply instead of DC) I've learned that they simply last longer if powered with DC through the rectifier.

Nearly any bridge rectifier will do. You're powering less than 20 watts at 25 volts (the transformers are rated at 50 watts). A typical rectifier can handle 1 amp at 200 volts, or 200 watts. Prices vary by vendor, but are usually only pennies apart from the same source, so get the bigger model so long as it fits physically. Besides, you may want one for another project.

LED's should last 100 years. Some will, some don't. The brighter the light, the more heat, and thus shorter life. They're really cheap, so some just fail for no reason after a few months or years. They also take 6 weeks to arrive from China, so rapid prototyping is not on the menu. Get a variety and see which ones you prefer before you order a big batch.

The round models are 3 watts or 5 watts. The "module" version is lower power and lower brightness, but runs much cooler. LED strips are able to spread heat out a little better. In other words, they come in all shapes and sizes. They're all pretty cheap. Ignore the fancy multicolored "reel" types -- they aren't bright enough.

LED's come in different "colors" of white. 3000 degrees Kelvin (3000K) is warm, yellow, orange-ish. 6000K is bright white, almost blue. Try both and see which you prefer. The warm ones look more like an old-time incandescent lamp, the white ones are brighter.

Search on eBay for "heatsink plaster" and "led round cob 3W 5W" and "adhesive LED 12v modules" and choose the 12-volt models. The plaster is not like ordinary heat sink grease. It dries hard, costs about $1 a tube, which should be enough for 3 or 4 assemblies.

I got lucky and found some aluminum heatsinks that were the right size, but that was a fluke. The round LED's are brighter, but hotter. The rectangular LED's have 4 or 6 lights on each module, aren't as bright, but don't seem to require a heat sink. Let them run for a few hours. If it's too hot to touch, it's too hot (this applies to nearly everything). If you've got an infrared thermometer, this is 120 degrees Fahrenheit.

You'll need a cheap solder pencil with a pointed tip and some electrical solder. If you've never soldered before, you can find YouTube videos to show you how. If your tip is a blade design or is too large, consider just filing it down with a metal file to make it the shape you wish. Solder pencils are cheap -- if you're paying over $10 for a pencil and some included solder, you're shopping in the wrong place. Keep the tip clean with a chunk of an old sponge you've soaked and squeezed out the excess water. Always tin the tip, the wire ends, and the solder pads before you solder them.

The top socket on our carriage lamps is actually just an ordinary lamp socket. I went to Home Depot and got some adapters that convert a lamp socket to a single two-prong electric outlet.

I got some replacement two-prong electric plugs that pop apart. You shove a piece of lamp cord inside and press the electric tabs together. Instead, I just tear the white plastic apart with a wire cutter and chop off the sharp little barbs on the copper pieces. I wrap and solder the "AC" leads on the bridge rectifier, one to each lead, around the top of the copper tabs, then shove them into the lamp socket adapter and glue them down.

The output leads from the bridge rectifier power the LED's. The sequence is:

The + Positive lead on the rectifier (which may be marked or simply be a shaved edge or corner on the package) goes to LED number 1 on it's + Positive marking.

The - Negative lead on LED number 1 is wired to the + Positive lead on LED number 2.

The - Negative lead on LED number 2 is wired to the - Negative lead on the rectifier.

The address signs have two automotive tail lamps in them. If one burns out, they both go dark, since they're wired in series.

There are tons of LED substitutes for tail lamps on eBay. Search for "led 194" and you'll find them. I prefer the flat style. There are cheaper versions with a rounded white plastic base, but after a few years, the plastic degrades from summer heat and winter cold and crumbles. That wouldn't be an issue, but they sometimes need to be jiggled around a bit to secure the connection, and if the base has crumbled it's a hassle. This is a task you want to do once and never have to do again. Get the solid style.

When installing the tail lamp LED's, simply tug the old lamps out. The LED's are polarized -- they only work if they're both plugged in exactly the right way. If they don't light, pull one out and twist it a half-turn and plug it back in. If they still don't light, twist the other one. If they still don't light, twist the first one again. Don't forget to cover the photocell on the pole each time to simulate darkness or nothing will light.

While you're at it, consider getting a few LED's for your car. These replace door lamps, marker lamps, some turn signal lamps, courtesy lamps, interior roof lamps, license plate lamps, etc. They're bright white and should last forever. Your night-time passengers will notice immediately. Sometimes the lamp is just a little too big to fit in a tight space; oh, well, they make little bitty ones, too. Sometimes the sockets get a little flaky months later and require re-insertion. To find out how to get your lamp assembly apart, look up marker lamp or license plate lamp and your car make and model on YouTube. Some imported cars require an entirely different kind of bulb that sort of looks like a round tube with pointed ends. Just Google lamp and your car make and model then search for that model lamp and LED on eBay.

Our lamps have a plug-in transformer in the basement to power them. It's a white square box, about 3" on each side. They're usually plugged in at or near a pull-chain lamp that's close to the outside pole with an adapter socket to add electric outlets to the lamp socket. This usually means there are two pull-chains. One turns off the electric sockets, the other turns off everything. Make sure the homeowner only pulls the cord that turns the basement lamp on and off or they'll accidentally turn off everything.

There is a wire cable connected to the bottom of the transformer that goes through the wall and out under the dirt. Sometimes people pull the wrong lamp chain and shut off the transformer as well as the light. You might consider shortening the "wrong" chain and lengthening the "proper" pull-chain to prevent inadvertently shutting off the lamp power.

These transformers have a special fuse built inside in case the wires get shorted. IF YOU SHORT THE WIRING, ANYWHERE, THE FUSE WILL BLOW AND IT CANNOT BE REPLACED ! ! !

This will require a new transformer, and they cost about $25 each. I got lucky and found an eBay auction of 3 for 20 bucks, so YMMV. This gives me a spare to test all my modules before I install them. You never know . . .

The lesson is, unplug the power if you're going to work on the system, if possible.

Some 25-volt transformers have a tiny green power lamp that shows they're working, some don't. If it appears there's no power to your carriage lamp, the AC power at the transformer may have been accidentally turned off, the transformer fuse may be blown, the wiring may be broken, or you may simply have corrosion in the lamp socket itself. I clean sockets with CRC spray, found in the auto supplies area at Home Depot.

One thing must be avoided at all costs.

If you insert a "standard" 120-volt incandescent lamp (a light bulb) into the carriage lamp, it will immediately blow the fuse in the transformer. Tell your neighbors, since the two bulbs look exactly alike. One is marked 120 and the other is marked 25.

My scheme has taken months to pursue, mostly waiting for shipments from China. There were a few setbacks along the way, mostly caused by heat, but some failures were just from chintzy LED manufacturing. But the parts are inexpensive, repairs are simple (just tear the old one off and glue and solder a new module).

Once you've found how to buy the parts, assemble and solder them, all that's left is making a finished product.

I use epoxy or glue to stick two heat sinks' fins together, use the "heatsink plaster" to stick the LED modules to the heat sinks, use some wooden sticks to mount those above the rectifier (that sits on top of the electric socket) and smear glue all over all the electrical connections to keep the weather out and strengthen the wood posts.

I use wood because it's easy to work with. I found a package of 100 wooden BBQ skewers at the Dollar Store and snap off whatever length I want.

My assemblies are so tall (because of the heat sinks) that I need to insert the top into the frosted globe first, then hold the globe up while I screw in the base.

If all the lamps are dark, the first suspect is loss of voltage or a faulty photocell. Check for power at the transformer and then at the wiring inside the pole -- landscaping projects and weed whackers are known to cut the underground wires. If you find the photocell has failed, just jumper over it to keep the lights on all the time. No one cares if it's on during the day. The amount of power drawn is very small -- the entire batch uses the same energy as a pair of 7-watt night lights, so even if they're on 24/7, it costs less than a dollar a month to power them.