Workstation 4 and 4 LX Field Service Guide
3-9
WS4 Troubleshooting
Testing the Power Supply and System Board Voltages
If a single ALWAYS voltage is missing, swap the power supply. If the
replacement power supply is missing the same voltage, this is likely a short on the
system board causing the power supply output to shut down.
On a system board where the ALWAYS voltages are present, but the board is
non-responsive, the on-board switched voltage regulators can be checked as
detailed in the next step. When the workstation is in the
NOPOWER
mode, these
regulators cut power to most system board devices.
Chapter 2 describes how the
ONCTL
and
ONCTL#
signals are used to control
the on-board switched regulators on the AB28 and ABRD36 system boards. To
check the working voltages on the AB28 System Board, see Step 2, below. To
check the working voltages on the ABRD36 System Board, see Step 3.
2.
If the ALWAYS voltages are present as shown in Figure 3-1, but the AB28 board
is non responsive, refer to Figure 3-2 and check the output of each on-board
voltage regulator.
Figure 3-2: Checking the AB28 System Board Series Working Voltages