ATT System 25 Maintenance Manual

CLEARING SYSTEM-DETECTED TROUBLES
Overheating Trouble
A clogged or dirty (or missing) air filter can cause the cabinet to overheat.
The cabinet air filter rests on the floor of the cabinet, under the CP carrier.
The air filter should be inspected on any service call and replaced as needed.
To replace the air filter, pinch it in the center and pull straight out.
Backplane and Cabinet Trouble
The backplane provides power, TDM bus connections, and telephone and
trunk interconnections. Each carrier has 12...

CLEARING SYSTEM-DETECTED TROUBLES
Figure 8-2. System Cabinet Backplane (Sheet 1 of 2)
8-19 

CLEARING SYSTEM-DETECTED TROUBLES
Figure 8-2. System Cabinet Backplane (Sheet 2 of 2)
8-20 

CLEARING SYSTEM-DETECTED TROUBLES
SYSBUSA0
SYSBUSA1
SYSBUSA2
SYSBUSA3
SYSBUSA4
SYSBUSA5
SYSBUSA6
SYSBUSA7
SYSBUSB0
SYSBUSB1
SYSBUSB2
SYSBUSB3
SYSBUSB4
SYSBUSB5
SYSBUSB6
SYSBUSB7354
353
352
351
350
349
348
347
346
345
344
343
342
341
340
339
TOSLOTS1-12SYSCLK337
SYSOCLK335
CLKSEL
334
SYSSYNC038
SYSFR036
BA4
BA3
BA2
BA1
SPARE-BUS034BA6 (GRD)220
BA5120020
019
119
219
BAO
319
LEGEND:
= BUSSED
102TA.0
BACKPLANE103TB.0
J58901A104TC.0
105TA.1
106TB.1
107TC.1
108TA.2109TB.2
110TC.2
111TA.3
112TB.3
113TC.3...

CLEARING SYSTEM-DETECTED TROUBLES
Figure 8-4. Power Designations On Cabinet Backplane
8-22 

CLEARING SYSTEM-DETECTED TROUBLES
Each of the 12 universal carrier slots has 48 pins on the backplane for
connection to station and trunk ports. The 48 pins are divided into eight
groups of 6 pins each, one group for each port circuit. Lead designations
consist of the lead name suffixed by the group number (for example, TA.2,
RA.2). Specific functions depend on the type of port card. Table 8-C
provides the 25-pin connector to backplane pin designations.
Manifestations of typical backplane problems...

CLEARING SYSTEM-DETECTED TROUBLES
Table 8-C. 25-Pair Connector to Backplane Designations
25-Pin Conn.CallGSLSTip RingATLMETBackplane
Pin No.WireProc.TrunkTrunkLineLineLinePin No.
ColorZTN76ZTN77ZTN78ZTN79TN735(Slots 1-12)
26W-BLRDA
T1T1T1T1T11021BL-WSGAR1R1R1R1R1002
27W-OCT1BT11032O-WDCDACR1BR1003
28W-GDTRAP-1LT1104
3G-WTDAP+1LTR1004
29W-BRRDBT2T2T2T2T2105
4BR-WSGBR2R2R2R2R2005
30W-SCT2BT2106
5S-WDCDBCR2BR200631R-BLDTRBP-2LT2107
6BL-RTDBP+2LTR2007
32R-ORDCT3T3T3T3T3108
7O-RSGCR3R3R3R3R3008...

CLEARING SYSTEM-DETECTED TROUBLES
Table 8-C. 25 Pair Connector to Backplane Designations (Contd)
8-25 

CLEARING SYSTEM-DETECTED TROUBLES
Emergency Transfer Unit Trouble
If the Emergency Transfer Unit (ETU) will not enter the power failure mode,
do the following steps:
1.Unplug the cable bringing the control signal from port seven/eight on
the Call Processor CP to the ETU. This cable terminates in a modular
jack that is inserted in a modular plug labeled CPU on the left-hand
side of the ETU.
2.If the ETU goes into the power failure mode, the Call Processor is
probably faulty or there is a wiring problem....

CLEARING USER-REPORTED TROUBLES
User-reported troubles are usually associated with voice or data terminal
equipment or trunks. They can result from system-detected errors and are
often solved by clearing system error conditions or alarms.
This section presents trouble-clearing techniques and procedures for user-
reported troubles.
Maintenance routines for data terminals and Asynchronous Data Units (ADUs)
are not contained in this section (although some basic routines for clearing
administration equipment...