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 universal slot positions. Any port
card can be installed in any slot. Connection to the corresponding
telephones or trunks is made through the backplane to the appropriate
cross-connect field.
DANGER:Hazardous voltages are present on some backplane pins.
Unplug power cord and wait at least 5 minutes before
removing rear cover.
Figure 8-2 provides a rear view of the cabinet backplane (rear cover must be
removed). Figures 8-3 and 8-4 show TDM signal designations and power
designations on the cabinet backplane.
Typical backplane pin designations are noted on Figure 8-2 for pins 355, 254,
and 056 located on slots 4, 3, and 1, respectively. Address plug locations for
Cabinets 1, 2, and 3 are also noted. The address plug position assigned slot
8 is reserved for future use. Seven leads (BA0-BA6, see Figure 8-3) are tied
to corresponding logic levels to uniquely identify each CP slot in the system,
including multiple cabinet systems. The logic values on leads BA4 and BA5
are used to identify the cabinet (Cabinet 1, 2, or 3) and are tied via the
cabinet address plugs to either +5 V dc or ground, as appropriate. Lead BA6
is tied to ground.
An address plug inserted on a cabinets backplane (pins 19 and 20) at slot
#5 designates the cabinet as Cabinet 1, slot #6 = Cabinet 2, and slot #7 =
Cabinet #3.
8-18 
						

							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
302TA.4
303TB.4
304TC.4
305TA.5
306TB.5
307TC.5
308TA.6
309
TB.6
310TC.6311TA.7
312TB.7
313TC.7
002
SLOTSRA.0
003RB.0
004RC.0
005
RA.1
006RB.1
007RC.1
008RA.2
009RB.2
010RC.2
011RA.3
012RB.3
013RC.3
202RA.4
203RB.4
204RC.4
205RA.5
206RB.5
207RC.5
208RA.6
209RB.6
210RC.6
211RA.7
212RB.7
213RC.7
TO
1-12
Figure 8-3. TDM Signal Designations On Cabinet Backplane
8-21 
						

							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 include power supply failure,
sudden failure of one or more circuit packs, or nonspecific system troubles
that cannot be isolated to a specific maintenance unit.
Backplane troubles are usually caused by bent or broken pins. A visual
inspection of the backplane may be adequate to determine if pins are bent or
broken. This may require removing one or more CPs.
Backplanes are not field repairable. A faulty backplane requires replacement
of the entire cabinet (but not the CPs in the cabinet).
8-23 
						

							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
33R-GCT3BT3109
8G-RDCDCCR3BR3009
34R-BRDTRCP-3LT3110
9BR-RTDCP+3LTR3010
35R-SRDDT4T4T4T4T411110
S-RSGDR4R4R4R4R401136BK-BLCT4BT411211BL-BKDCDDCR4BR4012
37BK-ODTRDP-4LT4113
12O-BKTDDP+4LTR4013
38BK-GT5T5T5T530213G-BKR5R5R5R5202
39BK-BRCT5303
14BR-BKCR5203
40BK-SP-530415S-BKP+520441Y-BLT6T6T6T630516BL-YR6R6R6R6205
42Y-OCT630617O-YCR6206
43Y-GP-630718G-YP+6207
44Y-BRT7T7T7T730819BR-YR7R7R7R7208
45Y-SETU48CT7309
20S-YETUGDCR7209
46V-BLETU48P-731021BL-VETUGDP+7210
47V-OT8T8T8T8311
22O-VR8R8R8R821148V-GETU48CT8312
23G-VETUGDCR8212
49V-BRETU48P-831324BR-VETUGDP+8213
50V-SGNDGNDGNDGNDGND300
25S-VGNDGNDGNDGNDGND200
8-24 
						

							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. Plug the cable back in,
then reset the Call Processor by removing and restoring power to the
system. If the ETU still does not go into the power failure mode, the
Call Processor CP must be replaced.
3.
If the ETU does not go into the power failure mode after the control
cable was unplugged in Step 1, the ETU is faulty and must be
replaced.
If the ETU remains in the power failure mode continuously (preventing normal
operation of the system), follow these steps:
1.At the ETU, unplug the cable bringing the control signal from the Call
Processor.
2.Using a modular jack breakout box and voltmeter, check to see that
48 volts is present between pins 1 and 2 and pins 3 and 6 of the
control cable from the Call Processor.
3.If the above voltages are present, the ETU is faulty and should be
replaced.
4.If the above voltages are not present, either the Call Processor or the
cable is faulty and should be replaced.
8-26 
						

							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 troubles are included). Manuals covering data
terminals and data modules are listed in Section 10 Reference
Documentation. Maintenance for auxiliary devices that are customer
provided is the responsibility of the user.
Administration Equipment Troubles
Administration equipment that is connected to the system on a dedicated
basis includes the System Administration Terminal (SAT), Station Message
Detail Recording (SMDR), and Digital Tape Unit.
Symptoms:
Terminal dead or functioning intermittently. Messages contain
garbage characters.
Procedures:
1.
2.
3.
4.
Check ac power connection.
Check cabling to cabinet.
Check administered settings for terminal from SAT (see
Administration Manual for your system). Settings should be for 8-bit
word length; no parity; space (0) for bit 8.
Check pin 20 of EIA connector for DTR signal. Signal should be
steady at greater than or equal to +3.0 volts with respect to pin 7
(ground).
9-1