3.6 SUGGESTED REPAIR ACTIONS
This section contains repair actions to be taken if a fault is found during functional testing
described in section 2.8. If the repair actions do not rectify the fault, refer to the maintenance
flow charts, section 3.5.
Before following repair actions check that the necessary circuit boards have been installed
boards ECPB, ECMB, EDTB,
and ETSB are necessary for the system to operate. An
ESTB-C board is required for each four stations and one ELNB-A board for each four exchange
lines. An EPFB board is required for each eight exchange lines. EXPB boards are necessary if
more than twelve exchange lines are fitted.
PBA Coding
Board ejectors are provided on
to facilitate their removal from the main equipment. The
board ejectors are coded into two categories.
RED EJECTORS: Boards with red ejectors must not be removed from the main equipment
until the mains power is turned OFF.
(ii)
EJECTORS: Boards with white ejectors may be removed from the system at any
In addition to the above categories, boards containing
circuitry are marked with a RED
LINE on the edge of the board and/or a “MOS” sticker on the ejector.
As previously mentioned these boards require careful handling and, in general, must NOT be
removed whilst the power is still on.
EXCHANGE LINE TESTS:
3.6.1
1.
2.
3.
4.
5.
6.
3.6.2
1.
2.
3.
4.
Line Seizure:
Check that the system has power and that station A is connected, check that the system is
not in programming mode
LED on DSS console must not be ON).
Check wiring from the main equipment to station. Check socket connections and wiring in
station as follows:
WIRE
W T
BL
RD
BK
610 SOCKET
CONNECTION IN
VOLTAGE
PIN NUMBER
STATION
wrt LBK
2
LWT
6
LBL
+
1
LRD
5
LBK
REF
Check the station fuse on the associated ESTB board, if the fuse is blown check wiring
(fuse is 0.375 AMP
Check voltages on the wires to the stations. If they are not similar to the above table,
change ESTB board.
Check the ribbon connector between the STB-B board and key pad assembly in the station.
Change station.
Line Seizure:
Check the wiring from the main equipment to exchange line. Check that the LED lights on
the ELNB board for the line (this indicates a DC loop).
Test exchange line.
Check receiver and its connections in the station. (White wires to
Replace ELNB board.
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