Workstation 5 Field Service Guide
3-17
Workstation 5 Troubleshooting
Checking the Power Supply and System Board Voltages
WS5 System Board - Working Voltages
On a unit where the Standby voltages are present, but fails to respond to the
power button, the Working domain voltages can be checked as outlined in
Figure 3-5, below and the following text.
Figure 3-5: Checking the System Board Working Voltages
The working voltages depend on the standby voltages. Before proceeding,
make sure all standby voltages shown in Figure 3-4 are available.
With AC power connected, press the power button and check the following.
1. Start with
PS_ON#
at the base of Q12 or Q13. It should be low.
o
Q12 and Q13 enable the
VCC3
and
VCC5
regulators, part of U38.
o
PS_ON#
is derived from the
WORKING
output of the Companion
Device. Q16 inverts
WORKING
to active-low
PS_ON#
(Sht. 8).
2. Check the
VCC3
and
VCC5
outputs at auxillary power connector J21. Pins 2
and 3 of J21 are ground. Watch those power supply heat sinks!
o
VCC3
(3.3V) is available at Pin-1 (towards the IO connectors)
