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R&M 2800 speed control


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Posted

This little 6” gem is an ac/dc universal motor. 
My fan runs on both AC and DC in only one position, the AC position. The DC position isn’t functioning. The “nichrome” element is damaged beyond repair. 
My question is what is the function of this nichrome element?  The fan is 1 speed only, ac/dc. 
My second question is:  Is there a resource to possibly repair this nichrome element?

Thank you

 

 

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Posted

You can use a half wave diode in place of the resistance wire to slow it down for second speed. 

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Posted

If the selections are "OFF AC DC" how is it two speeds? Probably just DC needs to be slowed. 

Posted (edited)
27 minutes ago, Michael Rathberger said:

If the selections are "OFF AC DC" how is it two speeds? Probably just DC needs to be slowed. 

The fan was not intended for two speeds from the factory. The resistance coil is for the DC setting as the fan would or was anticipated to operate faster on direct current. 

If his DC position is not working, he has an open in the resistance wire circuit.

However, in 2024 you can use the half wave diode in place of the resistance wire to gain a second slower speed of roughly 700 RPM. 🙂

Edited by Russ Huber
Posted

Russ, your explanation is appreciated. Did you happen to notice the position of your AC/DC selector is labeled different than my photo?

Can you recommend a diode rating for this application?

Posted
31 minutes ago, Malcolm MacGregor said:

Russ, your explanation is appreciated. Did you happen to notice the position of your AC/DC selector is labeled different than my photo?

Can you recommend a diode rating for this application?

Whatever position the lever is selected for that has the half wave diode inline from lever selection terminal contact to the motor will give you a lower speed. Find a half wave diode rated for 2.5-4 amp at 1000V (overkill). You can get them for peanuts on the web.

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