RSC type lamp receptacles which are commonly used in consumer lighting (and
some commercial) have been known to have this problem for many years. I use
thousands of halogen lamps and have even designed several. The problem with
the RSC's is that they rely on spring tension to make good electrical
contact as well as for mechanical mounting. This is a major no-no. The heat
generated in the tungsten to molybdenum joint just inside the lamp ends is
the culpret in that it heats the contact which then heats the spring contact
in the receptacle. The thermal cycling is fairly intense and the low-mas
spring suffers in the end. Just watch what happens on a scope when the
spring has weakened and the contacts arc, as you describe. I suspect this is
why so many of these fixtures with built-in dimmers also are found with dead
dimmers.

If you want to keep your lamp fixtures, you might just search and order
replacement RCS's. IMHO Ushio sells a well designed part.

Otherwise you might do like we do when designing commercial fixtures for
tubular IR Halogen lamps: use lamps with lead wires or tabbed contacts and
convert your fixtures to use different terminals. Either of these
suggestions should solve the bulk of the problem.

As a small side note, datasheets for most halogens call for a high limit on
the end seal temperatures. External forced-air cooling is almost always
needed to keep them within the spec.

I routinely operate halogens at less than the rated power. A Sylvania
Lighting Corp study showed that the gain in life far outweighs any
compromise in the halogen re-deposition cycle that is effected. The point
about occasionally running at full power is certainly a valid one. My newest
controllers have a mode selection in which they ramp up to 100% briefly each
time they start - before running at the setpoint value. The gains are even
greater with lamps designed for lighting only. The shorter wavelength =
higher color temp = higher filament temp, which allows the halogen cycle at
lower power settings. Bottom line is that between 60 & 90% of the rated
voltage, halogen lamp life can go from something like 190% to 300% of the
published life span. I have verified this in my own tests as well.

Soft-starting prevents virtually all of the catastrophic inrush related
filament and moly foil failures that kill most lamps. Well selected snubber
components clean up the balance of the causes. When all three measures are
applied, a 3,000 hour halogen can last up to 10,000 hours.

Of course it's all dependent upon good electrical connections...

chris

> I have a few halagon tochre lamps.  Inevitably a contact on
> one side of
> the lamp becomes corroded (pitted, from electrical arcing I assume)
> after a year or so of use.  This leads to poor and failing
> connections.
>  I've tried sanding down the contacts, and replaced another set.
>
> I was wondering if there exists a good set of contacts which won't
> suffer from this problem, or if it could be alleviated with conductive
> electrical grease (and are there high temperature greases which would
> work well).
>
> The obvious solution, of course, is to replace the lamps with energy
> saving, less heat emitting, non-dimmable flourescent lights.
> But I like
> the dimmability, the diffuse lighting (indirect from the ceiling), and
> the cheapness of these devices.
>
> Any suggestions would be appreciated.
>
> -Adam

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