A properly designed condenser enlarger has light-baffled air vents at the bottom and top of the lamp house. As air inside the housing heats, it rises upward and out of the upper exhaust vents. That rising air flowing out of the upper exhaust vents causes cooler ambient air to be drawn in through the lower air intake vents. This air flow limits the temperature inside the housing to a safe level.
For example, I have a Beseler 23C II enlarger equipped with the 75-watt PH-111 opal photo lamp. When the lamp is left on continuously for several minutes the housing gets warm, but not excessively so. The heated air flow rising out of the vents is noticeable by placing my hands above the vents. Even after several minutes of continuous operation the surface of the housing is warm to the touch, but not dangerously so. The cooling system is adequate to keep the lamp house at a safe temperature.
The maximum temperature inside the housing is proportional to the current rating of the bulb. It would be prudent to check the following (some of which have already been cited in previous posts):
1. The current rating of the bulb. This type and size of enlarger (probably 6 x 6cm given the name “Mars 66”) is most likely intended for a 75-watt opal photo lamp. If the lamp installed is of a higher current rating, changing the bulb will lower the operating temperature of the enlarger.
2. Verify that the air vents are not covered with something, such as packing material.
3. If it still runs too hot, you can install a variable bulb dimmer intended for conventional incandescent bulbs in the AC line. With this, you could reduce the current to the lamp to limit the heat to a tolerable level. Here’s an example that could be installed into a simple box housing and is inexpensive.
Last edited by Ian C; 03-02-2013 at 10:45 AM. Click to view previous post history.