Service manual

Theory
3-11
Regulator for -5 Volts
Certain analog components in the video section require a -5-volt supply. This is generated on-board
by a -5-volt switching regulator supplied by the +12-volt input.
Regulator for -3.3 Volts
Many digital devices on the CPU PCBA run on -3.3 volts. This is created from the +5-volt input by an
on-board switching regulator.
Power Supply Connector
Power arrives at the CPU PCBA via a single connector. The pin assignments for this connector on
the CPU PCBA are as follows:
Figure 3-6: Pin numbering for CPU PCBA connector
Table 1: Pin Assignments for Power Supply Connector
Pin Description
1 +5 V
2 +5 V
3 Ground
4 Ground
5 Remote sense line for the +5 V
6 +12 V
7 +12 V
8 PFAIL; power failure signal from the power supply
9 +5 V
10 +5 V UPS (Currently unused)
11 Ground
12 Grounded when plugged into display chassis;
used to detect what chassis the CPU PCBA is in
13 Ground
14 Ground
15 Power switch position
front view
18
15 9