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PDP-11/44 Troubleshooting Guide

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PDP-11X44 in its system cabinet (DEC)

Fault-finding on the PDP-11/44, from DEC's PDP-11/44 System Technical Manual (EK-KD11Z-TM-001), System User's Guide (EK-11044-UG-003) and BA11-A Mounting Box and Power System Technical Manual (EK-BA11A-TM-003).[1][2][3] Power faults are covered in more detail on PDP-11/44 Power Supply Guide.

Front panel indicators

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Indicators (EK-11044-UG-003, Table 2-1)
Indicator State Meaning
RUN On / off Processor executing instructions / halted
DC ON On DC power present and all voltages within limits
DC ON Blinking One or more voltages out of limits
DC ON Off DC power off
BATT On H7750 battery present and at least 90 % charged
BATT Slow blink Battery below 90 % and charging
BATT Fast blink Mains has failed; battery discharging; memory contents valid
BATT Off Battery discharged or absent; memory will be lost on a mains failure
REMOTE On CPU under control of the remote diagnosis unit

[4]

No power

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DEC's checks, in order:[5]

  1. Set the keyswitch to LOCAL, LOC DSBL or STD BY.
  2. Check the AC indicator on the 872-D or 872-E power controller. If it is out, check the mains outlet; if it is lit, check that the controller's breaker is on (1) and its LOCAL-ON/OFF/REMOTE-ON switch is at LOCAL-ON.
  3. If AC is still not switched through, unplug P1 or P2 from the power control bus on the controller. If pin 1 of P1 is open to ground, check the power control cable continuity from P1 to P2.
  4. Unplug P1 from J3 on the rear of the mounting box. If pin 1 of J3 is open to ground, the mounting box wiring is faulty.
  5. If pin 2 of P1 is grounded, a unit in the system or peripheral cabinet is reporting overtemperature.

Then check the DC voltages: +5 V at the connector end of the +5 V flexprint cable to the backplane, the others at P1 of the power flexprint cable. DEC's remedy for a DC failure is to replace the H7140.[5]

Diagnostics

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The CPU diagnostic ROM on the M7098 Unibus interface module runs when the front panel toggle is pressed to BOOT, when the boot command is typed at the console, or at power-up if switch S1 on the control module enables power-up boot. Tests 1 to 14 loop on error and tests 15 and 16 halt; halt the CPU from the console to read the loop address.[6]

CPU diagnostic ROM loop and halt addresses (EK-KD11Z-TM-001, Table 4-4, excerpt)
Address Test Failing area
165070 1 Unconditional branch
165172 5 Register data path
165346 14 JSR
165356 14 Push onto stack
165366, 165400, 165406 14 RTS, RTI, JMP
165526, 165550 15 Main memory data error without cache
165634, 165652 16 No hit in cache
165664 15 or 16 Parity error
165702 Any Hardware trap to 4 (check the stack)

[6] The cache can be disabled by hand with switches S1 and S2 on the cache module.[6] The MAINDEC diagnostics, run under XXDP+, should be run in DEC's order because each assumes the earlier ones passed: CKKFA (diagnostic ROM), CKKAA (CPU and EIS), CKKAB (traps), CKKTA and CKKTB (memory management), CZM9B (M9312/UBI boot), CKKUA (UBI map), CKKKA (KK11-B cache), CZMSD (MS11-M memory), CZDLD (serial lines), CKKAC (power fail), then CKFPA to CKFPC for the FP11-F.[7]

Console and serial line checks

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  • The console terminal interface on the M7090 can be jumpered for 20 mA current loop (active or passive) or RS-232C, RS-423 or RS-422 with jumper leads W1 to W20, which must match the terminal. Jumper W11 should always be fitted except for module testing.[8]
  • The LED on the M7090 lights once data has passed in both directions to the console terminal.[8]
  • The LED on the M7096 multifunction module lights at the start of a console self-test command and goes out when it completes.[9]

Grounding

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All units of the system should share one AC distribution source. If a grounding fault is suspected, measure between cabinet frames, and between a frame and the BA11-A box, with a voltmeter; DEC recommends a grounding strap between all cabinets.[10]

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References

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  1. ↑ Digital Equipment Corporation, PDP-11/44 System Technical Manual, EK-KD11Z-TM-001, December 1980 (File:PDP-11-44 System Technical Manual (EK-KD11Z-TM-001).pdf).
  2. ↑ Digital Equipment Corporation, PDP-11/44 System User's Guide, EK-11044-UG-003, July 1981 (File:PDP-11-44 System User's Guide (EK-11044-UG-003).pdf).
  3. ↑ Digital Equipment Corporation, BA11-A Mounting Box and Power System Technical Manual, EK-BA11A-TM-003, August 1983 (File:BA11-A Mounting Box and Power System Technical Manual (EK-BA11A-TM-003).pdf).
  4. ↑ DEC, EK-11044-UG-003, pp. 2-1 to 2-2, Table 2-1.
  5. ↑ 5.0 5.1 DEC, EK-KD11Z-TM-001, pp. 4-22 to 4-23, sections 4.8.1 and 4.8.2, power checks.
  6. ↑ 6.0 6.1 6.2 DEC, EK-KD11Z-TM-001, pp. 4-26 to 4-27, section 4.9.2 and Table 4-4, CPU diagnostic ROM.
  7. ↑ DEC, EK-KD11Z-TM-001, pp. 4-25 to 4-26, section 4.9.1 and Table 4-3, MAINDEC diagnostic programs.
  8. ↑ 8.0 8.1 DEC, EK-11044-UG-003, pp. 3-12 to 3-13, section 3.3.1 and Tables 3-10 and 3-11.
  9. ↑ DEC, EK-11044-UG-003, p. 3-13, section 3.3.2.
  10. ↑ DEC, EK-KD11Z-TM-001, p. 4-10, section 4.4.2, system grounding.
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