21 Sep
2011
21 Sep
'11
7:07 p.m.
Back when I repaired them (1988), more than 50% of the
units I worked
on had burned-out optical positioner lamps (and most of those, that
was the only part that needed replacing besides dirty filters). I
learned to power on the units and look down the open door - no light
meant I knew where to start.
And if you saw a flickering light from the rear right corner through the
door you powered down at once....
The blower fan runs off the mains, using the transformer primary winding
as an autotransformer on 230V mains. And it's on the 'hot' end of the
winding, so the fan motor's insulation has to withstand the full 230V.
Sometimes they don't and you get insulation breakdown. This starts as
sparka inaisw rhw motor, then the darn thing catches fire. Had to replace
a couple of those over the years...
-tony