Gear Graveyard April 1, 1999 Issue

Mysterious Cabin Lamp

Of late, there seems to be a spat of incidents involving electrical equipment that cooks itself. They may not be fire threats, but it’s worrisome.

The latest suspect is a cabin lamp sent to Gear Graveyard by a reader, David Hay, who lives aboard his boat in Florida.

The lamp, age unknown, appears to have melted some plastic around the metal bulb socket…and the white coating on the inside of the lacquered-brass, bell-shaped shade is scorched brown around the bulb base.

We found what seems to be the same lamp in the BOAT/U.S. catalog—a “Solid Brass Swivel Lamp,” 12V, 10-watts, standard two-prong bayonet bulb, rocker switch. We ordered one, for $18.95.

Both the BOAT/U.S. catalog and the shrink-wrap card the new lamp came on identify the supplier as SeaDog Line, of Everett, Washington.

Between David Hays’ failed lamp and the new one, some minor differences were noted.

One thing is clear: If the old model’s base was, when it was new and undamaged, like the new one, a considerable amount of several kinds of plastic—one white, one translucent—in the bulb base of David Hay’s lamp has melted and disappeared. All that’s left is a metal socket. It might be that the bare metal socket was all there was to begin with.

After photographing the pair, the new lamp was hooked up to a 12-volt-2.5-amp transformer and left in an unlikely position—with the open end of the shade pointed up. The more conventional position would be with the bell shade pointed down, which traps heat. That’s why lamps with a bulb in a tight housing often are designed to allow the heat to escape upward or have components (like a ceramic bulb socket) that can stand the heat build-up.

We placed a rectangle of paper on the up-turned shade, covering half the opening. The paper did not scorch or discolor.

Next, watching carefully, we covered the entire end of the shade. Nothing happened to the paper, but after two or three minutes, there was a noise and the light went out. The bulb had popped out of the base. Thinking that it had not been seated properly, we inserted it down against its two spring-loaded contacts, twisted it home in the bayonet slots, turned the lamp back on and replaced the paper. Again, in about three minutes, the bulb again popped loose.

Curious! No? Is there some overheat safety device built into the plastic socket? Perhaps the plastic ring expands when too hot, releasing its grip on the two pips on the bulb? But if a bit of heat pops out the bulb, what would happen if the lamp was in a more conventional position, with the bell pointed down. If would be annoying—reclused in your bunk, deep in the third volume of Marcel Proust—to get hit in the head by a hot light bulb.

But, when placed in the bell down position, nothing happened. The lamp worked very nicely. The bulb stayed put. No melting plastic. The shade didn’t even get too hot to touch.

There appears to be nothing whatsoever wrong with the new lamp.

It was tempting, at this point, to get off this rolling stone. But what if somebody inadvertently got and installed a more powerful (and hotter) replacement bulb?

The SeaDog lamp, as shown in the BOAT/U.S. catalog, has a 12-volt/10-watt bulb. The replacement bulb is shown as a 12-volt/7.5-watt that draws .8 amps.

We bought some Ancor bulbs and replaced the 10W bulb with an 18.4W bulb that draws 1.44A. They have the same bayonet base, but the 18.4W has a much larger glass portion.

Step #1, shade opening pointed up: In 2-1/2 minutes, the bulb popped out of the socket. We let it cool and proceeded to:

Step #2, shade pointed up, covered with paper, which because the bulb was much larger, touched the paper. The only result after 10 minutes was a very slight brown spot on the paper.

Step #3, the lamp in a normal, shade-down position. After seven minutes, the bulb was ejected. The bulb and the whole shade were too hot to touch. However, there appeared to be no damage.

Conclusion: It may not be dangerous (other than touch/burn), but the new SeaDog cabin lamp cannot handle an 18.4W bulb. We know not what kind of bulb (it must have been a hot one) was in Reader Hay’s old SeaDog lamp. We tried but couldn’t contact him.

Time for a call to SeaDog.

Craig Westlin, SeaDog’s O.E.M. manager, said the lamp was redesigned, and has a plastic socket to replace the prior metal socket.

“We’d certainly like to take a bow,” he added, “but if the new model has the advantage of ejecting improper bulbs, it is an entirely inadvertent safety bonus.”

Reader Hay’s candidate for Gear Graveyard, which we appreciate very much, turns out to be not a Gear Graveyard item. It is, however, a reminder that—as with so much equipment, especially electronic gear—a failed part should not be replaced with any one that fits, but with what is specified.

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