Xmotors

Have any pictures?

e r

As a kid I remember taking apart a phonograph - its C-frame shaded pole motor had a second winding that gave about 15V.

Michael

I can't find any, but...

That's it exactly, it's the same type of motor. :-)

Ah ok, so 220V winding on the motor plus CT 48 and 30V secondaries? (you mentioned +/- 24 and +/- 15V)

Michael

I'm not sure about the secondary voltages, but that sounds pretty close. The schematic doesn't show it.

BTW, I think these are also referred to as "fanformer", however I can't remember where I saw that [and google returns 1,000,'s of sports-related hits.]

The

Try a Google search on fanformer+voltage to get rid of the sports links.

Michael

wrote

Of course....that's better, thanks.

The same type of fan was employed in some brands of enclosed switch-mode power supplies in the 70's and 80's. It had disadvantages in dual input voltage range configurations, as it represents a serious energy 'leakage' on the open center tap of the voltage doubler in the

240V configuration - causing increased cap voltages under light loading - including the stalled fan condition that you identify as being beneficial to fault handling.

As a result it was usually backed up with bootstrapped housekeeping supplies and needed in internal minimum load circuit or other protection circuitry to avoid primary-side overvoltage.

This kind of fan isn't a big air mover, so I'm guessing that your noise problem is associated with aging bearings or distorted fan blades. The bearings require cleaning and lubrication, the blades can be replaced or a new fan assembly installed.

This kind of motor is typically open to the air - collecting dust on lubricated surfaces - a lousy feature in an air mover - and was considered a cost-cutting 'feature' in the days cheap clock motors.

RL