20 Watt Quartz-Halogen Conversion of American Optical Series 4 Illuminator
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The 20-Watt incandescent lamp in the standard AO Series 4 illuminator has a few drawbacks. The illumination is comparatively weak, there's a good bit of heat, and the bulbs are expensive to replace. I now believe an LED is the best solution, however, here is what can be done with a 20 watt quartz-halogen bulb. The illumination is better and there may be a little less heat generated. The main benefit is in the price of replacement bulbs.
The essential problem is that the original lamp is viewed from what I would call the top. Bi-pin quartz-halogen lamps must be addressed from the side, so a 90 degree angle is required.
Here's my solution:
1) Solid round stock:
a) cut to length
b) turn to the correct diameter
c) bore almost through
d) thread (with a shoulder) on the solid end
2) 3/4" sheet:
a) saw into an "L" shape
b) mill to finished shape
c) thread to fit the end of the bar
4) FIRMLY assemble the two pieces. You don't want them coming loose.
5) Finally:
a) mill a slot so that the wires can pass through the round
b) bevel and trim the "L" so that it can fit into a very tight space
c) drill and thread holes for lamp socket
I used a "universal' socket which will accept almost any width of pin configuration. I also placed spacers under the socket so that both short and long lamps could be used.
Here's the basic assembly:
Looking past the lamp, you can see the threaded joint:
'Wired and ready to go:
Installed and illuminated:
'Notice the bevel. The whole assembly needs
to move about freely for centration.
I removed this extra bit of metal to be on the safe side.
Eldred Spell
November 12, 2006
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