Sun Microsystems SPARCstation 2 Service Manual page 101

The wire colors are the following:
Red +5 V
Blue +12 V
Brown -12 V
Gray Por (Power On Reset from the power supply)
Black Ground
Note – The Por Signal is a TTL open collector and pull up is on the main logic
board.
The limits for the voltages are:
+5 V 4.90 V to 5.10 V
+12 V 11.16 V to 12.84 V
-12 V -11.16 V to -13.20 V with an internal drive
-12 V -10.20 V to -13.80 V without an internal drive
Do the following in sequence:
Turn the power off and connect the hard disk drive and diskette drive
°
power and data cables.
Turn the power on and again measure the power supply voltages. If the
°
voltages are correct, you have ruled out that the power supply is
defective. Go to step 12. If any of the voltages are incorrect, follow the
next step.
Disconnect each drive separately until the correct voltages are measured.
°
Replace the drive that is holding the voltage down.
With the power off, install the SBus boards that were removed earlier.
°
Turn on the power and measure the power supply voltages.
If any voltages are incorrect after installing the SBus boards, remove the
°
boards until the voltages are correct and replace the bad board. If the
voltages are correct, you have ruled out that the power supply is
defective.
13. Replace the system unit's cover.
To do this see "Replacing the System Unit's Cover" towards the end of this
chapter.
FRU Replacement
4
85