GLENTEK Inc. 208 Standard Street, El Segundo, California 90245, U.S.A. (310) 322-3026
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GA45-71PR2/76PR2/81PR2/82PR2 MANUAL
ENGINEERING NOTES FOR FAULT TRACING CHARTS:
NOTE 1:
To measure the DC bus voltage , carefully connect a voltmeter across the bleeder resistor attached to
the DC bus filter capacitor. The proper DC bus voltage for your amplifier is calculated by multiplying the AC power
input voltage on the main DC bus transformer by 1.4 (e.g. For 70 VAC input, you should read 70 X 1.4 or approx.
100 VDC bus voltage). The DC bus voltage will vary depending on if the motor is under a heavy or light load. The
DC bus voltage will sag under heavy loads. This is normal for unregulated DC power supplies.
NOTE 2:
The output voltage to the motor can be checked by alternately applying a positive and then negative
voltage to the signal input and observing the voltage swing at the amplifier motor output terminals. Keep in mind
that the Loop Gain and Signal potentiometers must be set at least somewhat CW. This test can be made with the
motor disconnected from the amplifier.
NOTE 3:
A low, but not zero, DC bus voltage could indicate an open or defective DC bus filter capacitor. To
check capacitor, remove from circuit and check with an ohmmeter. A visual check of the capacitor port seal could
show a blown pressure seal caused by a failed, overheated capacitor.
NOTE 4:
A blown 120VAC input fuse (F4) indicates a shorted fan, a blown low-voltage transformer (T301) or
possibly a shorted load on the transformer secondary. This transformer is located in the amplifier power section.
The transformer may be tested with the secondaries disconnected to isolate the fault.
Transformer terminal color-code:
BLK/BLK 120VAC 50/60 Hz primary
VIO/VIO 36VAC secondary for the control board
BLU 36VAC center tap
BRN/BRN 16VAC secondary to power module 301.
RED/RED 16VAC secondary to power module 302.
GRN/GRN 16VAC secondary to power module 303.
ORN/ORN 16VAC secondary to power module 304.
