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PDP-10 Power System Service

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KS10 backplane reference points and the H7130 power supply's terminals and adjustments (DEC KS10 Maintenance Guide)

Each PDP-10 processor has its own power system. The KA10 runs its FLIP CHIP logic from fixed +10 V and −15 V supplies in its cabinets and has a margin check system that substitutes a variable supply; the KI10 can vary its logic voltage under program control; the KS10 uses H7130 supplies and a BA11-K box for its Unibus.[1][2][3] The KL10's supplies are described on DECsystem-10 Power Supply Guide.

Warning: PDP-10 processors run from three-phase mains. Isolate the system at its breaker before opening a power supply, and allow stored charge to dissipate.[4]

Mains supply

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DEC's site guide specifies the supply for KA10 systems:[4]

  • 60 Hz systems: 115/200 V ±10%, 60 Hz ±2%, three-phase WYE. The KA10 takes three-phase, 4-wire plus ground, on 25 ft of 5-conductor cable with a Hubbell 3521 plug (mating receptacle Hubbell 3520); DEC recommends a 20 A circuit. Smaller units such as the TD10 take single phase on a Hubbell 3331 plug and a 30 A circuit.
  • 50 Hz systems: 230/400 V ±10%, 50 Hz ±2%, three-phase WYE. The KA10 has a 5-terminal block and 25 ft of 5-conductor cable, with no plug supplied; DEC recommends a 10 A circuit.
  • DEC suggests a separate breaker panel for the computer, with each 20 A or 30 A receptacle on its own breaker.

The KA10 itself draws 11 A, 11 A and 14 A on its three phases at 115 V (16 A on phase 1 with the punch running), surges to 25 A per phase, and dissipates 4300 W.[4]

KA10 supplies and margin checks

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The KA10's power supplies are bolted to a hinged frame inside each cabinet's rear door.[5] The system logic runs from +10 V and −15 V. The margin check system replaces these fixed voltages with the output of a Type 702 variable power supply: the five-position MARGIN CHECK switch on the maintenance panel selects the polarity of the margin voltage and feeds it to the left or right side of the system, and local switches beside each module panel select the +10 V or −15 V margin for that rack. The margin check meter reads the voltage applied to a panel accurately if margin switches are on in only one area of the machine.[1]

KA10 margin limits (DEC-10-HMAA-D Table 6-4, extract)
Panels +10 V margin, high +10 V margin, low −15 V margin, high −15 V margin, low
1A, 2A, 2M +12.0 V +8.0 V −17.0 V −13.0 V
Other panels in bays 1, 2 and 3 +17.5 V between +2.5 V and +5.5 V, depending on the panel −18.0 V −12.0 V

[1] DEC's table gives the limits for every panel, with special values for panel 1S during tests D, L and M and for the reader lamp supply in bay 3; use it when margining a particular rack.[1] Switching margin switches while a program runs can cause transients that alter registers or start a memory cycle; DEC's procedure is to press STOP, examine location 0, set the switches, press RESET, set the address switches to 4000 and press START.[6]

KI10

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The KI10 monitors all three phases for power failure and can restart automatically when power returns, and temperature sensors shut the system down if it overheats. Its DC logic supply can be set under program control to any of 64 levels, so diagnostics can run across a range of voltages without the margin switches of the KA10.[2]

KS10 (DECSYSTEM-2020)

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The KS10 backplane voltages are set on the left-hand H7130 power supply, measured at reference pins on the backplane:[3]

KS10 backplane power adjustments (KS10 Maintenance Guide)
Backplane pin Reference Adjust on the H7130
A09A2 +5 V V1
PT15 +5 V V2
B08U2 +12 V V3
B18B2 −5 V V5

[3] The H7130 has three terminal blocks: TB1-1 and TB1-2 carry AC, ground, power fail, on/off and the sense lines for the two main outputs, with a +5.1 V reference on TB1-2; TB1-3 carries the sense and output terminals for the +V3, −V3, +V4, −V4 and +V5 outputs. Potentiometers V1 to V5 adjust the outputs.[3] The guide's adjustment section also covers the BA11-K box that holds the KS10's Unibus options; its H765 power system and H744 regulators are described on PDP-11/34 Power Supply Restoration.[3]

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References

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  1. ↑ 1.0 1.1 1.2 1.3 DEC, DEC-10-HMAA-D, section 6.4, Figure 6-3 and Table 6-4, pp. 6-8 to 6-12. Margin check system and specifications.
  2. ↑ 2.0 2.1 Digital Equipment Corporation, DECsystem-10 Technical Summary, 1971, p. 49 (File:DECsystem-10 Technical Summary (1971).pdf). KI10 safety features and programmable margins.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Digital Equipment Corporation, KS10 Maintenance Guide, Volume I, EK-OKS10-MG-001, June 1979, checks/adjustments section, pp. 1–7: KS10 backplane power adjustment, H7130 power supply (MR-1916), BA11-K backplane power adjustments (File:KS10 Maintenance Guide Volume 1 (EK-OKS10-MG-001).pdf).
  4. ↑ 4.0 4.1 4.2 Digital Equipment Corporation, PDP-10 Site Preparation Guide, DEC-10-HAAB-D, May 1970, electrical requirements and KA10 data sheet (File:PDP-10 Site Preparation Guide (DEC-10-HAAB-D).pdf).
  5. ↑ Digital Equipment Corporation, PDP-10 KA10 Central Processor Maintenance Manual, Volume I, DEC-10-HMAA-D, December 1968, section 1.1.1 (File:PDP-10 KA10 Central Processor Maintenance Manual Volume I (DEC-10-HMAA-D).pdf).
  6. ↑ DEC, DEC-10-HMAA-D, section 6.4.2, p. 6-10.
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