"JB" wrote in message ...

[email protected] wrote in message
...
Hi,

I work in a nightclub and we have a bunch of old moving lights that still
work
okay except for lamp problems. They use arc lamps and it's not worth the
cost it
would take to get them in condition to fire the lamps again, plus there
is the
cost of the lamps, the cost of electricity to run them, and the damage
that the
heat does... I would like to try finding a really bright white LED light
source
to see if we can position it and make it work in our fixtures, if that's
a
practical thing to attempt. Can anyone tell me where I can find some
bright LED
light sources that might be suitable to try?

Sadly the optics in these type of 'moving light' projectors are not suited
to an LED retrofit, either optically or thermally. Quite apart from the
the high lumen output of the high pressure lamps currently in your
projectors [at least 10x to 20x that of a typical high power LED array],
the arc size is extremely small to facilitate good optical control [an LED
array of the similar lumens would be ~50mm diameter and useless for
imaging optics].
Basically an optical system has to be designed specifically for an LED
source for it to work correctly. The optics in your projectors are
designed specifically for short-arc, high pressure metal halide or ultra
high pressure mercury lamps, and are superb at what they do. Although as
you rightly say, the maintenenace isn't cheap.

JB

I work on these short arc discharge lamped moving heads, and it depends on
who makes them as to how expensive they are to repair. Some that I service
use electronic ballasts to control the lamp, and these are effectively quite
complex switch mode power supplies that produce around 100 volts AC at
anything up to 15 amps, depending on the power of the fitted lamp. They can
be quite challenging in terms of time, to get going again when they fail.
Parts-wise, they don't tend to use anything too special that you wouldn't
find in switchers in a more conventional application. Most of these units
also have another switcher in them to produce the DC volts for the DMX
control board, as well as the supplies for the stepper motor drivers (
there's a lot of motors in them to control pan, tilt, gobo selection, filter
selection, zoom, focus etc). Generally, these power supplies are pretty
conventional, and reliable. The motor driver boards fail, but again, they
are fairly straightforward, and not expensive, parts-wise, to repair.

Some other makes make use of conventional choke ballasts for controlling the
lamp, and these tend to be very straightforward. Often, the lamp igniter is
a sealed module, but some use discrete parts.

As to lamps, if you take the time to cast around on the net a bit, you can
reduce the silly money that some suppliers want for them, down to very
sensible levels. For sure, you will probably be buying a no-name rather than
a genuine Philips say, but it will perform just the same, and last nearly as
long.

As to modifying these lights to take a high power LED, I agree with JB's
summary - it's a non-starter. I think that you should take the trouble to
repair and refurbish them if you have the capability, or if not, at least
enquire what the cost of a professional repair on them would be.

Arfa