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TROUBLESHOOTING GUIDE
TROUBLE
CHECK
UNIT DOES
NOT RUN
AFTER DRIVE
MOTOR HAS
STARTED
1. Make certain 100 volts A.C. exists between terminals 1 (D signal) and 2 (Y2 signal) with the
power switch on. A voltage of approximately 16 volts D.C. between terminals 8 (P1 signal)
and 7(G1 signal) shows presence of the reference voltage. A voltage or approximately 90
volts D.C. between terminals 15 (K1/K3 signal) and 5 (F1/C1 signal) checks the power rectifi-
er bridge. If no D.C. power, or incorrect reference voltage is indicated, suspect trouble in the
control.
2. Make certain that the operator’s speed potentiometer is giving a reference signal to the con-
trol. No excitation of the coupling is possible unless the voltage between terminals 9 (R sig-
nal) and 7 (G1 signal) is at least .7 volt D.C. with terminal 9 (R signal) positive. The voltage
between terminals 9 (R signal) and 7 (G1 signal) will vary from 0 to 16 volts D.C. depending
upon the setting of the speed potentiometer.
3. Check for D.C. output voltage on coupling terminals 5 (F1/C1 signal) and 3 (F2/C2 signal).
With full excitation, terminal 3 (F2/C2 signal) will be as much as 90 volts D.C. positive. If exci-
tation is present, unit should be running unless the coupling coil circuit is open. To check for
open coupling coil, disconnect power to press and remove wires from control terminals 5
(F1/C1 signal) and 3 (F2/C2 signal). Connect ohmmeter leads to these two wires and check
resistance. Normal resistance is approximately 50 to 65 ohms. If measurement indicates
“open,” check coil connections inside motor drive conduit box. Also, recheck coil resistance
from this point. If coupling coil is “open,” contact local area motor repair shop for installation
of new coil.
4. Check setting of torque limit control.
UNIT SLOWLY
DRIFTS IN
SPEED
1. Torque Limiter may be set incorrectly. Reset torque limiting point per instructions in manual.
2. Check for worn speed control potentiometer or loose wiring connections between it and the
control terminal strip.
3. Operating drive at relatively low output speeds may cause excessive loading and resultant
slowdown.
4. Check for erratic tachometer feedback voltage, A.C., between terminals 7 (G1 signal) and 12
(G2 signal). Rapidly changing voltage here may be caused by loose connections, broken or
shorted wires, or a defective tachometer generator.
UNIT RUNS
ONLY AT FULL
DRIVE MOTOR
SPEED
1. Make certain problem is electrical. Check coupling excitation on terminals 5 (F1/C1 signal)
and 3 (F2/C2 signal). Use D.C. voltmeter (start with 0-150 V.D.C. scale). Connect positive
probe to terminal 3 (F2/C2 signal) and negative to 5 (F1/C1 signal). No excitation voltage
means unit is not energized electrically and problem could be mechanical within the drive.
2. Check D.C. voltage between terminals 9 (R signal) (+) and 7 (G1 signal) (-) to make certain it
is zero when the speed potentiometer is turned down. If not, external speed potentiometer
may be shorted or incorrectly connected.
3. Check for presence of tachometer feedback voltage, A.C., between terminals 7 (G1 signal)
and 12 (G2 signal). Without this feedback, unit will run at full speed with only a small refer-
ence voltage applied to terminal R. The tachometer feedback voltage varies from 30 to 60
volts A.C., depending on motor and drive.
4. Turn power switch off on control unit. If the drive remains running, the drive has failed either
through the center bearing locking up or the air gap in the coupling is closed. If this is the
case the motor will need to be repaired by a motor rebuild shop.
FUSES BLOW
1. If operator’s speed potentiometer is turned down and the fuse instantaneously blows an
internal failure may have occurred. Before replacing the unit, check for a direct short across
terminals 5 (F1/C1 signals) and 3 (F2/C2 signals) or terminals 4 (B2 signal) and 6 (C1 sig-
nal). A short indication at this point could be the result of a shorted coupling or brake coil,
lead, or associated component in that circuit.
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