4-46
888-2406-002
WARNING: Disconnect primary power prior to servicing.
Overall System Theory
A sample of the voltage across the discharge resistor is sent to the PS Controller at
J1-20 and J2-20. If the voltage is more than 30Vdc, the comparator will trip, and the
output at U1-1 or U1-2 will go LOW. The fault signal 1_DISCH_SAMPLE is then
sent to U9-2 where it is buffered before reaching the micro-controller. The PS
Controller would then shut down the power supply. The detection circuit contains
hysterisis to prevent false triggering.
4.7.5.5 RESET
There is a RESET line from the Life Support Board which is monitoring the
+20Vdc from the regulators on the Rectifier Boards. This is basically monitoring
the Low Voltage Power Supply. If the voltage falls below a set threshold, U37 on the
Life Support Board generates the RESET (active low) which is sent to all of the
controller boards (Master, PAC and PSC). On the PS Controller this RESET clears
U2 and U3, which brings their outputs low. This deactivates all of the DRIVER
signals, disconnecting all of the SCR taps and shutting off the supply. This also
activates the DISCHARGE(BAR) signal which then bleeds off the supply.
4.7.5.6 Watchdog Timer
The watchdog timer, U4 is basically looking for two things. First, it must receive a
pulse from the micro-controller every 1.0mSec. If it does not it will activate the
RESET line at TP4, and the supply will be shut off. It is also monitoring the +20Vdc
supply. If the voltage falls below the minimum limit of 12V, it will activate the
RESET line.
4.7.5.7 Analog Inputs
U7 acts as a linear amplifier and buffer for the analog inputs to the A/D converter
which is part of U6.
•
SAMPLE 1 and SAMPLE 2 are the voltage samples from the power supply. Pri-
marily it is used to control the power supply tap switching. However they are also
digitally filtered by the micro-controller by two filters. The first is a 50/60 HZ
band pass filter whose output is used to detect a loss of a rectifier fuse on the
transformer secondary, a non-critical fault. The second is a 100/120 Hz band pass
filter which is used to detect a severe primary phase imbalance or loss of phase.
Loss of phase is a critical fault which will shut the power supply off momentarily
(see “Power Supply Controller Faults” in Section 6 of this manual).
•
HEAT SINK THER(mistor) is the temperature sensor located on the rectifier
heatsink. If the heat sink temperature exceeds 100°C it will shut the power supply
off.
NOTE:
There are test points located after U7 which give a place to check the analog
voltages actually going into the A/D converter.
Summary of Contents for Platinum Z2 CD
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Page 70: ...3 14 888 2406 002 WARNING Disconnect primary power prior to servicing Operator Guide ...
Page 130: ...4 60 888 2406 002 WARNING Disconnect primary power prior to servicing Overall System Theory ...
Page 194: ...6 38 888 2406 002 WARNING Disconnect primary power prior to servicing Troubleshooting ...
Page 196: ...7 2 888 2406 002 WARNING Disconnect primary power prior to servicing Parts List ...
