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Old 10-30-2021, 10:39 PM   #1
cyclones
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Join Date: Feb 2010
City & State: Ames Iowa USA
Line Voltage: 120VAC 60Hz
Posts: 69
Default Motor control board repair

I have a motor control board I am trying to repair. I've been told the motor is fine, but the control board will only make the motor go one direction but not the other. Power comes in through a linear transformer and then a rectifier bridge and then filter caps. No schematics for the board. Relays on the board are 24V so I started by setting my bench PSU to 24V and injecting voltage. There are several LEDs. All but one LED lights up. There are test points labelled +15V, 0V and -15V. When checking voltage potential between +15V and 0V, I get a perfect 15V. For -15V to 0V, my meter shows approximately +1.15V. There are two voltage regulators with large heat sinks on the board. One gets warm, and the other is room temp. I think i will check for input to the cold voltage regulator next, but I'm trying to figure out why I'm getting the +1.15V reading on the -15V.
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