[ARC5] BC-348 Dynamotor

[K5MYJ]

A short on the output winding will act as a dynamic brake and cause the symptoms you are seeing.

Remove the brushes for the output winding and see how the motor runs. If it runs normally this way there is a short in the output circuit.

Bob Macklin
K5MYJ
Seattle, Wa.
"Real Radios Glow In The Dark"
  ----- Original Message ----- 
  From: Mark McKeown 
  To: ARC5 at mailman.qth.net 
  Sent: Friday, January 01, 2016 7:34 AM
  Subject: [ARC5] BC-348 Dynamotor


  Thanks to everybody for a fast reply!  I need to elaborate on what I have done.  Cleaned, lubricated bearings, checked for hanging brushes and weak springs, checked all the caps and checked the field for shorts and shorts to the frame.  The radio works fine on AC (I have an AC supply that can plug into the radio and replace the dynamotor.  The motor side of the armature was badly worn so I turned and undercut the commutator sections of the motor side and inspected closely for shorts. The dynamotor did work for about ten minutes and the radio did play fine.  The dynamotor speed then reduced significantly and runs a bit rough with very low voltage output and the unit gets hot fast drawing a lot of current.  Also sparks on the motor commutator while running.  Hope this clarifies a few things!  Thanks again for the help.


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