Sun Microsystems 1.0, Service Manual

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If the power cord and video cable connection are good and there is still no video
output, the system frame buffer (SBus card) or the monitor is the most likely
problem.
Symptom
Power on does not succeed
Actions
1. Turn the system power switch off.
2. Make sure that the system power cord is properly connected to the system rear
panel power receptacle and to the wall outlet.
3. Verify that the wall outlet is supplying AC power to the system.
4. Turn the system power switch on and observe the keyboard.
The four lights (LED) should briefly illuminate and you should hear a tone from
the keyboard.
If you hear no tone or see no lights on the keyboard, the system’s power supply may
be defective. Refer to the procedure “Power Supply Test” on page 24 later in this
chapter.
If you hear a tone and see lights on the keyboard, but the system still fails to
initialize, refer to the procedure “MLB Test” on page 26 later in this chapter.
Power Supply Test
Before you start make sure that the power supply is turned on. You need to remove
the system unit cover to be able to test the power supply. Refer to “Removing the
System Unit Cover” on page 32 in Chapter 4.
Use a VOM to check the power supply output voltages. The power supply connector
(J1501) must remain connected to the MLB. Place the VOM negative probe on one of
the logic ground pins in the connector, and test the +12V, -12V, and +5.1V power pins
individually with the positive probe. Table 3–1 lists the pin assignments on the
power supply connector.
24
SPARCstation 10 Service Manual
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Revision A, July 1993