Malfunctions Not Indicated by a Fault 3-33
115V Switching Power Supply (Series B)
The 115V switching power supply sources the +5V, +/-12V, and the +12V
ISO logic supplies used on the 1395 printed circuit boards. The power
supply circuitry is located on the right side of the PSI/Switcher board.
Failure of this circuitry will exhibit loss of functionality due to low or non
existent logic supplies, drive fault responses, and erratic operation. Follow
the procedure below if a switching power supply malfunction is suspected:
1. Measure the 115VAC source for the power supply. With a DMM on the
200VAC range, measure the voltage across pins 2 and 3 of TB2 on the
PSI/Switcher board. If 115V is not detected, check AC source. If 115V is
detected, check the condition of F1, in the upper left hand corner of the
PSI/Switcher board, and F3, to the left of TB2.
2. Measure the outputs of the supply on the test points located on the right
side of the PSI/Switcher board. With a DMM on the 20VDC range,
measure the logic supply levels shown in
Table 3.C with reference to
TP6.
Table 3.C Logic Supply Levels
If the +5V is outside of the tolerance, adjust the trimmer potentiometer
labeled R8 or 5V ADJ until it is inside specified tolerances. No
independent adjustment is available for the other outputs.
3. Verify that the logic supplies also exist on the Main Control Board at the
following test points:
Test Point Voltage Low Limit High Limit
TP1 +12V DC +11.85V DC +13.13V DC
TP2 +5.00V DC +4.98V DC +5.02V DC
TP4 –12V DC –11.85V DC –13.13V DC
Test Point Measurement
TP51 +5V logic supply can be monitored with a DVM. Its signal level should be +5.00
VDC 0.02VDC in respect to TP52
TP52 Digital logic supply common can be monitored with a DVM. Its signal level
should be +0V DC in respect to TE. This signal is used as the reference for
measuring all isolated signals.
TP53 Isolated supply common can be monitored with a DVM. Its signal level should
+0V DC in respect to TE. This signal is used as the reference for measuring all
isolated signals.
TP54 Isolated +12V supply can be monitored with a DVM. Its signal level should be
between 11.85 and 13.13 VDC in respect to TP53.
TP55 +12V logic supply can be monitored with a DVM. Its signal level should be
between 11.85 and 13.13 VDC in respect to TP57.
TP56 -12V logic supply can be monitored with a DVM. Its signal level should be
between 11.85 and 13.13 VDC in respect to TP57.
TP57 Analog supply common can be monitored with a DVM. ITs signal level should be
+0VDC in respect to TE. This signal is used as the reference for measuring all
analog signals.
TP58 +5V isolated supply can be monitored with a DVM. Its signal level should be
+5.00V DC 0.02 VDC in respect to TP53.
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