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Old 11-10-2021, 12:59 PM   #18
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Join Date: Jun 2012
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Default Re: Motor control board repair

107vac is likely that they have 3 phase power supplying the building and they use one phase to supply the board, this is normal.
Locate the source for the -15v, trace the -15volt point back, the ac for this circuit is likely supplied from the transformer and then through a diode or bridge to give a negative voltage.
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