Zenith Z-100 PC series Service Manual page 7

Chapter 3
Theory of Operation
Introduction
Refer to Figure 3.1 while reading the following.
The power supply provides regulated voltages used by the various compo­
nents within the Z-100 PC Series Computers. The power supply is located
toward the rear and to the right of the chassis, and uses a quasi square
wave switching regulator to produce three regulated output voltages. This
unit complies with FCC, VDE, CSA, and UL regulations.
Outputs
All outputs from the precision-regulated power supply are electrically iso­
lated from the main voltage and share a common ground, which is the
chassis of the power supply.
The voltages output to disk drive connectors P1 and P2 have special
requirements for output ripple frequency components in the frequency
range of 60 to 120 KHz. To obtain these low levels, a low pass filter
is added to the regular output leads of P1 and P2. The output ripple is
measured with an oscilloscope with a bandwidth of 3 KHz. Component
frequency of the output ripple of the 5-volt or 12-volt outputs should NOT
exceed 2 mV peak between the frequencies of 60 KHz to 120 KHz. Con­
nector P3 supplies the output voltages to the backplane board.