The difference with the option 003 is that a DC fan is fitted rather than the mains (50/60 Hz) AC one in the standard unit. This give you more choice of replacment fan. Take the old one out and see what model it is. Any modern DC fan of the right size and voltage will work.
The OPT 003 fan can't be a 400Hz unit because it still has to run at 48Hz. There is no such thing as a 48Hz to 400Hz AC fan (unless it is really a DC fan with built in power supply).? I've actually used / installed HP and Tektronix kit on aircraft using the 400Hz supply.?
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Robert G8RPI
