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Step 5. Connect the common lead of the oscilloscope to J13, pin 8.
Measure the Power Supply Sync signal (PS_SYNC) on J13,
pin 14:
Specification: 2-4 vpp Sine Wave at 109.89 KHz
NOTE
The power supply module will power-up without the
PS_SYNC signal being present. However, the lack of this
signal will introduce signal purity problems when the sys
-
tem is performing measurements.
Power Supply Module
Check
If any of the DC voltage tests fail, verify that the power supply module is
operating properly with minimal impact from the system as described in
the procedures below.
NOTE
If a power supply voltage is low, it may be due to excessive
current draw from the system and not a fault in the power
supply.
Steps 1 through 4 verify the operation of the + 9, ±18, and ±27 Vdc
supplies:
Step 1.
Press the 373XXA Power key off, and and disconnect the
power input cord.
Step 2. Disconnect the power supply module from the A17 Mother-
board at J4.
Step 3. Reconnect the power line input cord to the system and
press the 373XXA Power key on.
Step 4. Using a DMM and/or an oscilloscope, measure the power
supply voltages at the power supply connector pins that
correspond to the Motherboard pins for the + 9, ±18, and
±27 Vdc supplies. Refer to Table 5-1 and Figure 5-1 (previ
-
ous page).
Steps 5 through 8 check the +5 volt supply. This power supply re
-
quires at least a 10% load to turn on. Therefore, at least one of the dig
-
ital PCBs A9, A13, or A14 (which use the 5 volt supply) must be in
-
stalled in the system during this procedure.
Step 5.
Press the 373XXA Power key off, and reconnect the power
supply module to the Motherboard at J4.
Step 6. Unplug digital PCB’s A13 and A14.
Step 7.
Press the 373XXA Power key on.
SYSTEM DOES NOT POWER-UP TROUBLESHOOTING
5-6 373XXA MM