LLZ 421
Operation and Maintenance Repair
ILS 420
6−29Ed. 01.10
SOAC
6.6.2 Correcting a Processor Standstill
See Fig. 6−5.
A processor standstill may result when subassemblies are removed under voltage or on account of
static charges which are discharged from the operators to the rack. This condition is always the result
of an operator error. It is therefore advisable to pinpoint the causes as soon as it happens. There are
in fact only four possible causes, though these may occur in combination.
− Insufficient grounding of the rack
− Unsuitable and/or incorrectly cleaned floor covering
− Non−observance of clothing regulations by personnel
− Carelessness of the personnel due to inadequate information.
Any causes determined should be remedied immediately by means of appropriate measures: the
symptom will not then recur. A distinction should be made in case of a processor standstill between
a failure in the monitor processor and a failure in the transmitter processor. Both the behavior of the
system and the measures to be taken are different.
6.6.2.1 Failure in the Monitor Processor
The LCP shows MON1 FAULTY or MON2 FAULTY due to to the failed processor. If both monitors fail,
the transmitter will be shut down. Remedy:
− Open front door of the rack.
− LED CPU_Normal on the LG−M must light (flashing). If it is off, press button board reset on LG−M.
− Close door again.
− Perform login and enter password if more commands must be entered, otherwise this step may
be ignored.
The installation should be fully operational again.
6.6.2.2 Failure in the Transmitter Processor
If lamps light up on the system in a manner which has no meaning and cannot be interpreted, then
go out again after a short time, then the processor has fallen out of synchronism temporarily on
account of an interference pulse, but has been able to recover. If this symptom is encountered repeat-
edly, the causes should be determined. If the transmitter fails on account of a processor standstill,
this is displayed by means of TX1 or TX2 WARNING on the LCP. Remedy:
− Open front door of the rack.
− LED CPU_Normal on the LG−A must light (flashing). If it is off, press button board reset on LG−A.
− Close door again.
− Perform login and enter password if more commands must be entered, otherwise this step may
be ignored.
The installation should be fully operational again.
6.6.2.3 Failure in the LC−CPU Processor (LCP)
If the LCP screen is dark and keys on front panel do not function a LCP−processor fails on account
of a processor standstill, a first measure is to reset the LC−CPU board. Remedy:
− Open front door of the rack.
− Live LED on LC−CPU must light. If it is off, press button board reset on LC−CPU.
− Close door again.
The installation should be fully operational again.
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