Power-On Does Not Succeed; Power Supply Test - Sun Microsystems SPARCstation 4 Service Manual

4.2

Power-On Does Not Succeed

1. Turn off the system power switch.
2. Check that the system power cord is properly connected to the system rear panel
power receptacle and to the wall outlet.
3. Verify with a VOM that the wall outlet is supplying AC power to
the system.
4. Turn the rear panel system power switch on and observe the keyboard.
The LEDs on the keyboard should briefly light. You should hear a tone from the
keyboard. If you have a Sun Type-5 keyboard, there is a Standby power key that you
may also press to see if the system can be powered on or not. Only try the Standby
power key if the rear switch fails to turn on the system.
If you hear no tone or see no lights on the keyboard, the system's power supply may
be defective. See Section 4.2.1 "Power Supply Test."
If you hear a tone and see lights on the keyboard, but the system still fails to
initialize, see Section 4.2.2 "System Board Test."
4.2.1

Power Supply Test

1. Use a VOM (volt-ohmmeter) to check the power supply output voltages.
Place the VOM negative probe on logic ground pin 15 in the connector, and test the
+12V, –12V, and +5V power pins individually with the positive probe (pins 1
through 3). See
Note – The power supply must remain connected to the system board during this
test. This allows the power supply to regulate the voltages.
2. Replace the power supply assembly if any of the voltages are not present.
See Section 8.1 "Power Supply."
and
FIGURE 4-1 TABLE 4-2
.
Chapter 4 Troubleshooting Procedures 4-3