universal motor speed control

[gjo]

I have a circuit diagram of a speed controller for a universal motor. I am having trouble uploading the picture, so i will do my best to describe it. It has a potentiometer feeding a capacitor that will trigger a diac to turn on the triac.my question is in the diagram the rc series circuit isin series with the motor, so why doesnt the motor run even if triac is burned open?

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http://books.google.com/books?id=vmg1UKsTntAC&pg=SA5-PA150&lpg=SA5-PA156&ots=BrHfQCWkWW&focus=viewport&dq=reasons+why+universal+motor+with+speed+control+not+running&output=html_text

The diagram is on page 5_150

 

[chuckey]

How do you know the triac has burnt open? Possibley the transient suppression network components are short circuit?
Frank