DECsystem-10 General Maintenance
Routine care and preventive maintenance for a DECsystem-10, from DEC's own maintenance documents: the MH10 Maintenance Manual (EK-MH10-MM-003), the KL10 Maintenance Guide (EK-OKL10-MG-003), the KL10-C power system description (EK-PWR20-SD-001) and the 1971 DECsystem-10 Technical Summary.[1][2][3][4] For the supplies themselves see DECsystem-10 Power Supply Guide.
Site
edit- Power. A KL10-C processor needs three-phase five-wire power within +6% and −12% of nominal at up to 60 A per phase, on a line separate from lighting and air conditioning; DEC refers site planning to its DECsystem-10 Site Preparation Guide (EK-DEC10-SP-003).[5] Each MH10 memory cabinet adds 20 A at 120 V (175 A inrush for one cycle) and dissipates 2400 W.[6]
- Grounding. DEC connects the KL10-C cabinet grounding point to the building ground, and runs a No. 4 gauge ground mesh cable from the copper bolt on the bottom of each MH10 to its neighbours.[5][7]
- Temperature. DEC's MH10 operating range is 15–35 °C, storage 5–45 °C, and DEC requires memory tests and adjustments to be made at 20–30 °C.[6][8]
- Weight. A single MH10 cabinet weighs 409 kg and stands 1.83 m high.[6]
Cooling and interlocks
editAir flow is monitored. The KL10-C power control shuts the system down if any of four air-flow sensors reports insufficient flow or a cooling-assembly door is open, and MH10 cabinets do the same through four air-flow switches and door-panel interlocks.[9][10] Keep fans running freely and air filters clean: DEC's monthly visual inspection of the MH10 is for broken wires, connectors and other defects, free-running fans and unclogged filters.[8] The override switches that bypass these interlocks are for maintenance only; with them on, the power lamps blink or flash as a warning.[9][10]
Preventive maintenance schedule
editDEC's schedule for the MH10 core memory:[8]
| Task | Interval | What DEC specifies |
|---|---|---|
| Visual inspection | Monthly | Modules and backplane for broken wires and connectors; fans running freely; filters not clogged |
| MAINDEC diagnostics | Monthly | Run the memory diagnostics with no errors |
| Strobe and drive current margins | Quarterly | MAINDEC-10-DDMMG error-free at HIGH and LOW for each of the STRB, THRESH and CUR margin switches, one switch at a time per cabinet |
| Voltage measurements | Quarterly | +20 V, +5 V and −5 V at the module backplane, each within ±5% |
| Sense strobe delay | Quarterly | 160 ns ±20% after the X read driver turns on, measured on the G236 driver module |
| Drive current | Quarterly | 335 mV ±15% below +5 V between AK2 and +5 V on the G236, at 25 °C |
| Delay check | Quarterly | ADR ACK and DATA WARNING timing to drawings D-BS-MH10-0-ISO |
[8] DEC's test instruments for this work were a Tektronix 453 oscilloscope and a 0.5% digital voltmeter. DEC also warns to switch all power off before inserting or removing modules, and to route the flat 40-way sense-inhibit cables so that the logic cabinet doors do not pinch them.[8]
Core memory handling
editThe G236 driver, G116 and H224 modules of each 32K stack set are adjusted together at the factory. If one fails, DEC replaces all three as a matched set, and the jumpers on the G236 that set strobe margin and bias current are not to be changed in the field.[8][11] Each 64K bank of an MH10 has a select switch: a bank switched out moves to the top of the cabinet's address range so the remaining memory stays contiguous, which lets a system run with a failed stack until it can be repaired.[6]
Memory bus cables use Quick Latch connectors; DEC warns not to force them, and each unused access port is terminated with an H866 terminator.[7]
Voltage margins
editThe KI10 can set its logic supply voltage under program control to any of 64 levels, so its diagnostics run at margins without manual adjustment.[12] MH10 memories have maintenance-panel margin switches: STRB moves the sense strobe by ±7 ns to expose marginal core switching speed, THRESH varies the sense amplifier threshold to expose core noise or low output, and CUR varies the X/Y selection currents by ±7.5%. A DIR switch selects the high or low direction.[13] They are used with the memory diagnostic as above.[8]
Indicator lamps
editThe KI10 processor cabinet carries hundreds of incandescent indicator lamps. CompuServe, which ran many DECsystem-10s, replaced them with LED lamp modules to save power, heat and lamp changes, and DEC followed.[14]
Console front end (KL10)
editOn KL10 systems a PDP-11/40 front end boots and monitors the KL10 and runs DEC's diagnostics; its own disk or floppy drives and LA36 console need their own care.[15][9] See Floppy Drive Repair and Hard Drive Maintenance and Repair.
Related pages
editReferences
edit- ↑ Digital Equipment Corporation, MH10 Maintenance Manual, EK-MH10-MM-003, August 1977 (File:MH10 Core Memory Maintenance Manual (EK-MH10-MM-003).pdf).
- ↑ Digital Equipment Corporation, KL10 Maintenance Guide, Volume I, EK-OKL10-MG-003, April 1985 (File:KL10 Maintenance Guide Volume 1 (EK-OKL10-MG-003).pdf).
- ↑ Digital Equipment Corporation, DECSYSTEM-20 Power System, System Description, EK-PWR20-SD-001, April 1976 (File:KL10-C Power System Description (EK-PWR20-SD-001).pdf).
- ↑ Digital Equipment Corporation, DECsystem-10 Technical Summary, 1971 (File:DECsystem-10 Technical Summary (1971).pdf).
- ↑ 5.0 5.1 DEC, EK-PWR20-SD-001, pp. PWR20/1-4 and 1-13. Electrical requirements and grounding of the KL10-C.
- ↑ 6.0 6.1 6.2 6.3 DEC, EK-MH10-MM-003, pp. 1-1 to 1-8, Table 1-1. Description, bank select switches, specifications.
- ↑ 7.0 7.1 DEC, EK-MH10-MM-003, pp. 2-2 to 2-3. Memory bus cables and terminators, AC power, ground mesh cable.
- ↑ 8.0 8.1 8.2 8.3 8.4 8.5 8.6 DEC, EK-MH10-MM-003, pp. 5-1 to 5-3, sections 5.3 and 5.4. Preventive maintenance and corrective maintenance.
- ↑ 9.0 9.1 9.2 DEC, EK-PWR20-SD-001, pp. PWR20/2-1 to 2-10. Power control, fault conditions, override, switch panel.
- ↑ 10.0 10.1 DEC, EK-MH10-MM-003, pp. 4-34 to 4-36. 857 power control, air-flow and door interlocks, override switches.
- ↑ DEC, EK-MH10-MM-003, p. 5-1, section 5.2. Jumper configuration on the G236 driver module.
- ↑ DEC, DECsystem-10 Technical Summary, 1971, p. 49. Programmable voltage margins.
- ↑ DEC, EK-MH10-MM-003, p. 3-6, Table 3-4, "Maintenance Panel Switches".
- ↑ "PDP-10", Wikipedia, section "Use by CompuServe", en.wikipedia.org/wiki/PDP-10.
- ↑ Digital Equipment Corporation, DECsystem-1080/1090 System Description, EK-1080U-SD-003, January 1977, section 4.3, bitsavers.org. Console processor subsystem.