Main Logic Board Voltage Test Points - Sun Microsystems SPARCclassic Service Manual

Main Logic Board Voltage Test Points

There are no voltage test points on the main logic board. If you need to measure
voltages, the safest place is at the power supply connection on the main logic board
(see Figure 11–12 and Figure 11–13). See "Before Replacing the Main Logic Board" on
page 128 for the connector wiring and voltages.
Caution - Printed circuit boards are made of delicate electronic components that are
extremely sensitive to static electricity. Ordinary amounts of static from your clothes
or work environment can destroy the boards. Handle boards only by the
nonconducting edges. Do not touch the components themselves or any metal parts.
Always wear a grounding (wrist) strap when handling the boards. Attach the wrist
strap to the metal casing of the power supply at the rear of the unit top.
Caution - The AC power cord should remain attached between the system unit and
an AC wall outlet. This connection provides the ground path necessary to protect
internal system components from harmful static discharges. Inside the system unit,
be sure the power supply wiring harness is connected to the main logic board to
complete the ground.
Caution - Verify that the system power switch is in the Standby position. The green
LED at the front of the system unit should not be lit and the fan should not be
running. When the system power switch is in the Standby position, and the AC
power cord remains connected to a power outlet, hazardous AC voltage is still
present in the power supply primary. Do not attempt to service the power supply
under these conditions. Disconnect the AC power cord prior to handling the power
supply. When servicing any other system component, the AC power cord should
remain connected and poses no safety hazard.
Main Logic Board and Component Replacement
125