Trouble shooting, Manufactured by – Precision Control Systems 1025 User Manual
Page 10
MODEL 1022 & 1025
7
05/10/2007
TROUBLE SHOOTING
CAUTION: High voltage exists on the supply and load terminals of this controller and may exist on other equipment
located near the controller. Use extreme caution to avoid electrical shock.
The LED located on the controller circuit can be used to aid in determining problems. This LED varies in intensity
proportional to the command signal and therefore should be proportional to the load voltage.
THE FOLLOWING ARE SYMPTOMS AND POSSIBLE CAUSES:
SYMPTOMS
POSSIBLE CAUSES
NO LOAD POWER, LED not ON:
Determine that the command sigal is applied to the
controller. Determine that 24 volts is applied to the circuit.
NO LOAD POWER, LED intensity can be varied:
Determine that all fuses are “OK”. If the voltage across the
SCR module is equal to the line voltage the SCR module
has probably failed. NOTE: If a replacement SCR module
is ordered specify the voltage and current rating of the
controller and the serial number of the failed unit.
LOAD POWER IS MAXIMUM AND CANNOT BE
REDUCED, LED is ON:
Determine that the command signal can be adjusted to
zero. Also remove the green plug-in connector to remove
the command signal. If the LED is not off, the circuit card
has failed.
LOAD POWER IS MAXIMUM AND CANNOT BE
REDUCED, LED is OFF:
Remove the 24Vac plug in connector. If the load still has
power the SCR module has probably failed as a short
allowing full power at be applied to the load. To determine
if the SCR module has shorted remove power and then
the line and load connections and measure the resistance
across the line and load terminals on the SCR module. If
the resistance is less than 10000 ohms the modual has
failed. NOTE: If a replacement SCR module is ordered
specify the voltage and current rating of the controller and
the serial number of the failed unit.
LOAD VOLTAGE SNAPS ON:
Determine that the primary of the circuit transformer is
connected to the same supply as the controller and load.
MAXIMUM LOAD VOLTAGE CANNOT BE OBTAINED:
Determine that the primary of the circuit transformer is
connected to the same supply as the controller and load.
Typically this problem is caused by the primary being
connected across the load and line connection at the
controller.
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