4-10
888-2595-001
12/20/11
WARNING: Disconnect primary power prior to servicing.
Section 4 Theory of Operation
ZX Series
Comparators U1C and U1D perform a similar function as U1B for PA modules 7 and 6,
respectively. Similar circuits for PA modules P5 through PA 1 on pages 2 and 3 of the
schematic.
The output of all PS modules are shared via diode-or connection to power the IPA
module and cooling fans via the SHARED_50V line. The +5V output of all PS
modules are shared via a common connection of their A1 pins. Circuits internal to the
PS modules allow these outputs to be tied together without need for external diodes.
A voltage sample of the SHARED_50V line is developed by divider R53-R26 (page 4)
and passed by buffer U4C through RFI network R2-C13-R3 and J9-7 to the PA_VOLTS
line.
50V power is passed to the cooling fans at the chassis rear door via connector
J10. A FAN_STATE logic level reported from the fan monitor board on the rear door is
compared to a +2.5V reference from voltage divider R39-R40 by comparator U4B.
U4B provides logic level inversion, converting a low = alarm condition from the fan
monitor PCB to a high = alarm condition at its output. This output is passed via RFI
network R8-C8-R9 and J9-10 to the FAN_FAULT line to signal that at least one fan has
insufficient speed / rpms.
Comparator U4D generates a module fault (PA module shutdown) alarm on the
controller board whenever it senses that the MODULE_OFF signal line at J9-9 is being
held low by any of the backplane boards.
4.9
5X Fan Monitor PCB
Consult drawing 801-0203-441
The fan monitor PCB provides 50V distribution and fault checking for up to five DC
fans. It is designed to work exclusively with the DV6448/12 model fan.
Fault checking for fan 1 is done via the internal tachometer line on J1-3. The signal
from the fan tachometer is RFI filtered via network R26-C22 and pre-conditioned via
network C17-R31-CR15-Q1. The tachometer sample at the drain of Q1 is a square
wave with a frequency proportional to the fan speed in rpms. This signal is analyzed by
missing pulse detector U1 with a period equal to approximately 150% of the period at
full fan speed. The output of U1 goes low whenever the next transition of the
tachometer square wave does not appear before the end of the current period (i.e. fan
rpms less than 2/3 of nominal value). This low condition lights alarm LED DS1 on the
rear door and is passed via steering diode CR1 and J6-2 to the FAN_STATE logic line.
Similar circuits provide the same functionality for fans 2-5.
Содержание ZX10
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Страница 18: ...Table of Contents Continued 4 ...
Страница 80: ...3 12 888 2595 001 12 20 11 WARNING Disconnect primary power prior to servicing Section 3 Operation ZX Series ...
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Страница 174: ...7 12 888 2595 001 12 20 11 WARNING Disconnect primary power prior to servicing Section 7 Parts List ZX Series ...