B Holdover Clock Troubleshooting Procedures
B.1 Introduction
Most alarm conditions in the holdover clock are not out-of service or service-affecting conditions. The system is designed with redundant power, reference inputs, clock input cards, stratum clock cards and output card protection switching.
The only true out-of-service condition is when all power is lost to a shelf, or all reference inputs and both stratum clock cards fail. Before taking any action on the system, such as removing cards, first consider the following troubleshooting guidelines:
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Do not touch the shelf until you have analyzed the condition and know the possible result of any planned corrective actions.
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Do not touch the shelf until you have been properly grounded.
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Both major and minor alarms in the shelf require immediate attention. But, very few alarms in the holdover clock system are service affecting. Improper corrective actions could be service affecting.
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Do not remove an ST3 clock card from the shelf, unless you are certain it is the cause of the condition. This is especially true if the ST clock card(s) is (are) in the holdover mode (the HOLD OV/HOLDOVER lamp is lit, or the HOLD OV/HOLDOVER and INP TOL lamps are lit). Removing both ST clock cards in this condition causes total loss of all outputs from the shelf and/or system.
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Write down any alarm and normal lamp conditions in the shelf. These will help you to determine where to look for the cause of the condition.
B.2 Interpreting System Alarms, Lamps And Trouble Isolation
Alarms generated by the holdover clock are reported through the Eagle. All alarm conditions are defined in Corrective Maintenance.
When troubleshooting, write down all abnormal and normal lamp conditions for the shelf with the alarm lamp lit on the SAI card. This will assist in analyzing and isolating the cause of the condition. Do not start removing or replacing cards to attempt to clear alarms, as it could lead to crashing EAGLE.
Tables to aid in troubleshooting are listed in the following sections. Once the basic trouble has been isolated and it has been determined that an individual card is defective, perform the appropriate card replacement procedure in Card Removal/Replacement Procedures.
Table B-1 Input and ST3 Alarm Conditions
| SAI/MISLAMPS | ABNORMAL CARD LAMPS | ACTIVATED OFFICE ALARMS AND SHELF STATUS | ACTIVATED CLOCK STATUS A AND B | CONDITION TYPE # (NOTE) |
|---|---|---|---|---|
|
MAJOR and MINOR lit |
ST3 A and B = FAIL, LOCK, and REF B lit |
Visual = MAJOR and MINOR Shelf Status = MAJSI, MINSI, and CLKL. (HOLDOVERALARM switch SW3 on backplane is set to MAJ or MIN) |
None |
1 |
|
MAJOR and MINOR lit |
Input cards A and B = FAIL lit, frequency/bit rate lamp off, SRFL lit (ACI only) ST3 A and B = FAIL, LOCK, and REF B lit |
Visual = MAJOR and MINOR Shelf Status = MAJSI, MINSI, and CLKL. (HOLDOVERALARM switch SW3 on backplane is set to MAJ or MIN) |
None |
2 |
|
MINOR lit |
Input card A or B = FAIL lit, frequency/bit rate lamp off or lit, SRFL lit (ACI only) ST3 A and B = REF (A or B) lamp lit (associated with input card with FAIL lamp off) |
Visual = MINOR Shelf Status = MINSI, and CLKL (HOLDOVERALARM switch SW3 on backplane is set to MAJ or MIN) |
None |
3 |
|
MINOR lit |
ST3 A and B = LOCK lit |
Visual = MINOR Shelf Status = MINSI (HOLDOVERALARM switch SW3 on backplane is set to MAJ or MIN) |
None |
4 |
|
MINOR periodically lights, then goes off |
Input card A and/or B = FAIL periodically goes on and off. First occurrence only the SRCACT/SRCACTIVE on FAIL card goes off and lights on the other card. |
Visual = Periodic MINOR Shelf Status = Periodic MINSI and CLKL ( HOLDOVERALARM switch SW3 on backplane set to MAJ or MIN) |
None |
5 |
|
MAJOR lit |
ST3 A or B = FAIL lit |
Visual = MAJOR Shelf Status = MAJSI (HOLDOVERALARM switch SW3 on backplane is set to MAJ or MIN) |
None |
6 |
|
For the corrective action to take for each condition type, refer to Table B-2. |
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Table B-2 Input and ST3 Corrective Actions
| CONDITIONTYPE # (From ) | CONDITION AND PROBABLE CAUSE | CORRECTIVE ACTION |
|---|---|---|
|
1 |
No input cards installed. Outputs are as accurate as free-running clock cards. Timed network elements reporting high slip rate. |
Install at least one input card.(See Appendix A). |
|
2 |
Input references A and B have failed (frequency/bit rate lamp off) or have exceeded BPV, OOF, or excessive zeros parameters (frequency/bit rate lamp lit). |
Check input reference connections at the shelf and source ends. Reconnect if required. Isolate and repair input reference facilities, if required. |
|
The input reference facility framing format rearranged from D4 to ESF, or vice versa, and the input card options were not changed to match it. |
Change the option switch settings to match the current framing format. See Installation Guide. |
|
|
The input reference has been recently reassigned, and the signal amplitude is too high. |
Wire a 100 ohm, 1/4 watt resistor across T and R input terminals on the shelf backplane. |
|
|
Both input cards have failed. |
Replace both input cards (See Appendix A). |
|
|
3 |
Input reference A or B has failed (frequency/bit rate lamp off) or has exceeded BPV, OOF, or excessive zeros parameters (frequency/bit rate lamp lit). |
Check input reference connections at the shelf and source ends. Reconnect if required. Isolate and repair input reference A or B facility (if required). |
|
Input card A or B has failed. |
Replace the input card with the FAIL lamp lit (See Appendix A). |
|
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The input reference facility framing format rearranged from D4 to ESF, or vice versa, and the input card options were not changed to match it. |
Change the option switch settings to match the current framing format. |
|
|
The input reference has been recently reassigned, and the signal amplitude is too high. |
Wire a 100 ohm, 1/4 watt resistor across T and R input terminals on the shelf backplane. |
|
|
4 |
Active input reference has exceeded pull-in range of ST3 cards. Timed network elements reporting high slip rate. |
Press transfer (XFR) pushbutton on either input card to switch SRC (source) ACTIVE lamp to the other input card. ST3 A and B LOCK lamps go off in less than 40 seconds. Isolate source of frequency offset on input reference facility and repair. |
|
5 |
Input reference facility (A and/or B) line coding rearranged from AMI to B8ZS and input card(s) option switches were not set to match the change. Input card BPV spec periodically exceeded. |
Change input card(s) option switch settings from AMI to B8ZS. |
|
6 |
ST3 A or B card has failed and squelched its outputs. Outputs are receiving their reference from the ST3 with its FAIL lamp off. Outputs are not affected. |
Replace the ST3 card (A or B) with the FAIL lamp lit (Appendix A). |
Note:
For a description of each condition type, refer to Table B-3.Table B-3 Shelf and Output Alarm Conditions - Not Related to Input and ST Conditions
| SAI/MISLAMPS | ABNORMAL SHELF AND CARD LAMPS | ACTIVATED OFFICE ALARMS AND SHELF STATUS | ACTIVATEDCLOCK STATUSA AND B | CONDITIONTYPE # (NOTE) |
|---|---|---|---|---|
|
None lit |
All lamps on all cards are off |
Visual = CRITICAL (MISONLY), MAJOR, and MINOR Shelf Status = CRTSI (MIS only), MAJSI, MINSI, and BATTALM |
None |
1 |
|
MINOR lit |
MCA-5 = All 10 PORTALM lamps lit |
Visual = MINOR Shelf Status = MINSI |
None |
2 |
|
MINOR lit |
Any TO card = PORTALM lit Output protection pushbutton lamps = Lamp over TO card with PORTALM lit, and like HSTO card light for a short period of time (approx 3 seconds) then goes off MCA-5 = AUTO lamp flashes for approx 6 seconds when HS protection switch is activated and released. |
Visual = MINOR Shelf Status = MINSI and PRTA (SW1 positions 3 and 5 on MCA-5 set to MAJ or MIN) |
None |
3 |
|
MINOR lit |
Shelf fuse A or B = Lamp lit |
Visual = MINOR Shelf Status = MINSI, and BATTALM. POWERALARM switch SW2 on backplane is set to MIN) |
None |
4 |
|
MAJOR lit |
Any TO, ST, or MCA-5 = FAIL lit |
Visual = MAJOR Shelf Status = MAJSI (MCA-5 SW1, positions 3 and 5 set to MAJ) |
Visual = MAJOR Shelf Status = MAJSI (MCA-5 SW1, positions 3 and 5 set to MAJ) |
5 |
|
FAIL and MAJOR lit (MIS only) |
MIS = FAIL lit |
Visual = MAJOR Shelf Status = MAJSI |
None |
5 |
|
MAJOR and MINOR lit |
Shelf fuse A or B = Lamp lit |
Visual = MAJOR Shelf Status = MAJSI, MINSI, and BATTALM. (POWERALARM switch SW2 on backplane is set to MAJ) |
None |
4 |
|
MAJOR and MINOR lit |
Any TO card = FAIL lamp lit Output protection pushbutton lamp = Lamps lit over TO with FAIL lamp lit and like HSTO card (HS protection switch activated). |
Visual = MAJOR and MINOR Shelf Status = MAJSI and MINSI (MCA-5 SW1, positions 3 and 5 set to MIN) |
None |
5 |
|
MAJOR and MINOR lit or MINOR lit or None lit (MAJOR and MINOR lit if MCA-5 SW1, positions 3 and 5 set to MAJ; if SW1 set to MIN, then MIN lit; if set to NOALARM, then None lit) |
Output protection pushbutton lamps = Lamps over TO cards and HS cards alternately light and then go off. |
Visual = MAJOR and MINOR or MINOR or None Shelf Status = MAJSI and MINSI or MINSI or None (MAJOR and MINOR if MCA-5 card SW1 set to MAJ; MINOR if SW1 set to MIN; none if SW1 set to NOALARM) |
None |
6 |
|
MINOR lit or MAJOR and MINOR lit (MINOR if MCA-5 SW1, positions 3 and 5, are set to MIN or NOALARM; MAJOR and MINOR lit if set to MAJ) |
Any TO card = PORTALM lit Output protection pushbutton lamps = Lamps lit over TO card with PORTALM lit, and like HSTO card. |
Visual = MINOR or MAJOR and MINOR Shelf Status = MINSI and PRTA or MAJSI, MINSI, and PRTA (MINOR if SW1 positions 3 and 5 on MCA-5 set to MIN or NOALARM; MAJOR and MINOR if set to MAJ) |
None |
7 |
|
MINOR lit or MAJOR lit or None lit (MINOR lit if MCA-5 SW1, positions 3 and 5 set to MIN; if SW1 set to MAJ, then MAJOR is lit; if set to NOALARM, then None lit) |
Output protection pushbutton lamps = Lamps lit over a TO card and like HSTO cards MCA-5 = MAN lamp is flashing |
Visual = MINOR or MAJOR or None Shelf Status = MINSI or MAJSI or None (MINOR lit if MCA-5 SW1, positions 3 and 5 set to MIN; if SW1 set to MAJ, then MAJOR is lit; if set to NOALARM, then None lit) |
None |
8 |
Note:
For the corrective action to take for each condition type, refer to Table B-4.Table B-4 Shelf and Output Corrective Actions - Not Related to Input and ST Conditions
| CONDITIONTYPE # (FROM ) | CONDITION AND PROBABLE CAUSE | CORRECTIVE ACTIONS |
|---|---|---|
|
1 |
Loss of Battery A and B to shelf. All outputs are squelched. Causes could be from operating error, office battery source failure, blown fuses, or a component failure, e.g., isolation diode which shorts battery to battery return. |
1. Determine cause of loss of battery and repair. 2. Restore office battery source. 3. Replace blown fuses in battery distribution bays, miscellaneous fuse bays, and panels, and/or on DCD shelf. |
|
2 |
Communication between MCA-5 and TO cards is not functioning. Microprocessor on the MCA-5 is failed or garbled. Does not affect outputs. Automatic TO protection switching function disabled. Manual TO protection switching function is still operational. |
1. No TO cards in shelf. Install at least one TO card. 2. No input references or input cards, and no clock cards installed. Install at least one clock (ST) card (See Appendix A.) 3. MCA-5 communications bus or microprocessor garbled. Remove and reinsert the MCA-5 card to clear bus and microprocessor. 4. MCA-5 microprocessor failed. Replace MCA-5 card (Appendix A). |
|
3 |
HS protection switch activated, then released because of: • Unterminated cable on TOTA or TOTL output, or, • Shorted cable on TO output. When the condition occurred, an HS protection switch was activated, PORTALM on TO goes off, and lights on the HSTO card, output protection pushbutton lamps over the TO and HS light, MCA-5 AUTO lamp flashes, HS protection switch releases, PORTALM on HSTO goes off and lights on TO, output protection pushbutton lamps go off, and MCA-5 AUTO lamp stops flashing (duration = 3 to 6 seconds). Non-failed ports on TO with PORTALM lit lost output for one millisecond during HS protection switch activation and release. Failed TO port is out of service. |
1. Press and hold the output protection pushbutton over the TO card with PORTALM lamp lit. MCA-5 lights PORTALM lamp(s) of failed TO port. Release pushbutton. 2. Isolate and repair cable or NE connected to that TO port. 3. If port connection is new and not yet terminated at NE, then either insert disabling pin in that port’s disabling jack on TO card faceplate, or remove cable from output wire-wrap panel, or place an appropriate resistor termination across tip (T) and ring (R) of cable at NE end, until ready to connect cable at NE end. |
|
4 |
Loss of Battery A or B to shelf. Does not affect outputs. Causes could be from operating error, blown fuse, or a component failure, e.g., isolation diode which shorts battery to battery return. |
1. Determine cause of loss of battery and repair. 2. Replace blown fuses in battery distribution bays, miscellaneous fuse bays, and panels, and/or on DCD shelf. |
|
5 |
Card with FAIL lamp lit has failed, except for input card which causes a MINOR alarm when its FAIL lamp lights. Outputs are not affected if MCA-5 and HS slots are equipped. |
Replace the card with the FAIL lamp lit (Appendix A). Release HS protection switch, if activated, by pressing lit HS pushbutton until switch releases. |
|
6 |
A TO card’s microprocessor has lost its ability to process data. The TO cards are alternately being switched to HS protection and then released. One millisecond loss of outputs each time a TO is switched to or released from HS protection. |
Manually switch each TO card to the HS, replace the TO card (Appendix A) and release the HS switch. Continue until the malfunctioning TO card is located and removed from the shelf. |
|
7 |
Output port failed on TO card with PORTALM lamp lit. HS protection switch activated. Loss of output on failed port. Other output on same TO lost for one millisecond when HS protection switch activated. When condition occurred, an HS protection switch was activated, PORTALM lamp on TO card remained lit, output protection pushbutton lamps over TO and HS slots lit, and MCA-5 card’s AUTO lamp flashes for 6 seconds and then lights steady. |
1. Press and hold the output protection pushbutton over the TO card with the PORTALM lamp lit. MCA-5 lights PORTALM lamp(s) of failed TO port. Release pushbutton. 2. Remove TO card with PORTALM lamp lit. 3. Set option switch settings on the replacement TO card identical to settings on removed TO card. 4. Insert replacement TO card in shelf slot and wait 10 seconds for TO to warm-up. Verify ST, INPUT and OPTION lamps are lit and PORTALM and/or FAIL lamps are not lit. 5. Press output protection pushbutton over HSTO until pushbutton lamps go out (releases HS switch). MCA-5 card’s AUTO lamp flashes for 6 seconds and then lights steady. |
|
8 |
TO card manually switched to HSTO card |
Release the manual HS switch by pressing the lit pushbutton over the HSTO card for 3 seconds. |
Note:
For a description of each condition type, refer to Table B-3.