Watchdog Timer; Analog Inputs; Ps Controller Faults; Life Support Board - Harris Platinum Z16HD+ Preliminary Manual

Section 4 Overall System Theory
of the SCR taps and shutting off the supply. This also activates the DISCHARGE(BAR)
signal which then bleeds off the supply.
4.8.6.6
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 supplies 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.
4.8.6.7
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 Rectifier Boards. Pri-
marily they are used to control the power supply tap switching. However they are
also digitally filtered by the micro by two filters. The first is a 50 to 60 HZ band pass
filter whose output is used to detect a loss of a rectifier fuse on the transformer sec-
ondary, a non-critical fault. The second is a 100 to 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 heat-
sink. If the heat sink temperature exceeds 100°C it will shut the power supply off.
NOTE:
There are test points located after U7 which provide a location to check the ana-
log voltages actually going into the A/D converter.
4.8.6.8
For a complete listing of all of the faults associated with the PS Controller Boards refer
to Section VI, Troubleshooting.
4.8.7
The microprocessor control system is backed up by the Life Support Board. The Life
Support Board allows safe transmitter operation at reduced power if the Master
Controller is not operating. The transmitter does require that the PA and PS Controller
Boards be operational to control the power supplies and PAs.
The Life Support Board has two basic modes of operation:
4-56
WARNING: Disconnect primary power prior to servicing.

Watchdog Timer

Analog Inputs

PS Controller Faults

Life Support Board

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Platinum Z16HD+
9/15/06