Editing PDP-11/20 Documentation

'''PDP-11/20 Documentation''' describes the Digital Equipment Corporation manuals for the [[PDP-11/20]], with the PDF of each. DEC issued the 11/20 documentation as a basic series: a system manual, a manual for each major component, and a second volume of engineering drawings for each.<ref name="sm" />

== PDP-11/20 System Manual (DEC-11-HR1B-D) ==
DEC's overview of the basic 11/20 system, sixth printing May 1973 (first printing August 1970), 27 pages scanned without a text layer.<ref name="sm" />

Contents: 1 introduction, applicable documents (Table 1-1) and the master drawing list (Table 1-2); 2 system description, with the basic system and its variations (Tables 2-1 and 2-2) and specifications of the KA11 processor, KY11-A console, MM11-E core memory, KL11 Teletype control, H720 power supply (Table 2-7) and Unibus (Table 2-8); 3 system operation, console controls and indicators and their interactions; 4 operating procedures: manual and automatic loading, the bootstrap loader, running programs and Teletype operation.<ref name="sm" />

It has no circuit descriptions or adjustment procedures; those are in the component manuals.

<pdf width="800" height="500">File:PDP-11-20 System Manual (DEC-11-HR1B-D).pdf</pdf>

Download: [[:File:PDP-11-20 System Manual (DEC-11-HR1B-D).pdf|PDP-11-20 System Manual (DEC-11-HR1B-D).pdf]]

== KA11 Processor Manual (DEC-11-HR2B-D) ==
DEC's manual for the 11/20 processor, fifth printing May 1972 (first printing September 1970), 91 pages scanned.<ref name="ka" /> Chapters 1 to 4 give the theory of operation of the KA11, its instruction execution and the power-fail logic. Chapter 5, maintenance, lists the engineering drawings and test equipment, explains module identification and layout, multiple-box systems and power control, and gives the processor clock adjustment, the KA11 removal procedure and maintenance tips on the MAINDEC diagnostics and the KM11 maintenance set.<ref name="ka" /> The logic drawings themselves are in the separate KA11 engineering drawing volume, not in this scan.

<pdf width="800" height="500">File:KA11 Processor Manual (DEC-11-HR2B-D).pdf</pdf>

Download: [[:File:KA11 Processor Manual (DEC-11-HR2B-D).pdf|KA11 Processor Manual (DEC-11-HR2B-D).pdf]]

== MM11-E Core Memory Manual (DEC-11-HR3A-D) ==
DEC's manual for the 4K-word core memory of the basic 11/20, first printing August 1970, 43 pages scanned.<ref name="mm" /> Chapter 1 introduces the memory, chapter 2 gives the theory of operation of the core array, drivers, sense amplifiers and timing, and chapter 3 covers maintenance: the V REF, V SLICE and STROBE DEL adjustments (Table 3-1, p. 3-1), the sense, inhibit and drive waveforms with failure waveforms dotted in (Figures 3-2 and 3-3), and a troubleshooting chart of symptoms, causes and corrective actions (Table 3-2). Chapter 4 holds the engineering drawings.<ref name="mm" />

<pdf width="800" height="500">File:MM11-E Core Memory Manual (DEC-11-HR3A-D).pdf</pdf>

Download: [[:File:MM11-E Core Memory Manual (DEC-11-HR3A-D).pdf|MM11-E Core Memory Manual (DEC-11-HR3A-D).pdf]]

== H720 Power Supply and Mounting Box Manual (DEC-11-HR5B-D) ==
DEC's manual for the H720 supply and the BA11 boxes, fifth printing November 1972 (first printing August 1970), 26 pages scanned.<ref name="h720" />

Contents: 1 introduction; 2 power supply: models (Table 2-1), AC power distribution and the unregulated supplies, block diagram description of the switching regulators, overcurrent and crowbar protection, AC LO and DC LO, and a detailed circuit description with the driver, differential amplifier, crowbar, AC LO and DC LO schematics (pp. 2-1 to 2-8); 3 mounting box and its models (Table 3-1); 4 installation: configurations (Table 4-1), space, environment, power and cable requirements, installation steps, and data sheets for the PDP-11/20 models, LT33 and LT35 Teletypes, the H720 (p. 4-9), the H960-CA cabinet, the H952-HA table and the extension boxes.<ref name="h720" />

It gives no parts list or component values; for those use the drawings below.

<pdf width="800" height="500">File:H720 Power Supply and Mounting Box Manual (DEC-11-HR5B-D).pdf</pdf>

Download: [[:File:H720 Power Supply and Mounting Box Manual (DEC-11-HR5B-D).pdf|H720 Power Supply and Mounting Box Manual (DEC-11-HR5B-D).pdf]]

== H720 Power Supply and Mounting Box Engineering Drawings ==
The drawing volume that goes with the H720 manual, first edition March 1971, 38 pages.<ref name="drw" /> The drawing index lists the H720 assembly (D-UA-H720-0-0) and parts list (A-PL-H720-0-0), the H720 circuit schematic (D-CS-H720-0-1), the power regulator board assemblies for the A and B models (D-CS-5408475-0-1) and the E and F models (D-CS-5409267-0-1), the PDP-11 basic assembly, cabinet, KY11-A, KY11-B and KY11-C console, table and BA11 chassis drawings.<ref name="drw" /> The second half of the scan holds Teletype ASR-33 modification, alignment, acceptance, packing and installation procedures.

The circuit schematic on PDF page 10 carries the parts list with the reservoir capacitors, fuses, bridge rectifiers and switching transistors, and the regulator board schematic on page 11 has the value of every capacitor on the board. These are the source for the parts tables on [[PDP-11/20 Power Supply Service]].<ref name="drw" />

<pdf width="800" height="500">File:H720 Power Supply and Mounting Box Engineering Drawings (1971).pdf</pdf>

Download: [[:File:H720 Power Supply and Mounting Box Engineering Drawings (1971).pdf|H720 Power Supply and Mounting Box Engineering Drawings (1971).pdf]]

== PDP-11/20 price list (1 November 1970) ==
DEC's eight-page US price list for the PDP-11/20, effective 1 November 1970: the six standard system models with their contents, memories (MM11-E, F, H, J and the interleaved EX and FX), bootstrap loaders, and options and peripherals with their mounting and power requirements.<ref name="pl" />

<pdf width="800" height="500">File:PDP-11-20 Price List (1 November 1970).pdf</pdf>

Download: [[:File:PDP-11-20 Price List (1 November 1970).pdf|PDP-11-20 Price List (1 November 1970).pdf]]

== Not hosted here ==
Bitsavers also holds the September 1970 printing of the KA11 manual, the 11/20 system schematics of February 1970, the KY11-A console manual, the KE11-A extended arithmetic element and KT11-B paging option manuals, and module schematics.<ref name="bits" /> The MM11-F, MM11-S and other core memory manuals are in its pdp11/memory directory.

== Pages that cite these documents ==
* [[PDP-11/20]] – specifications, models and prices
* [[PDP-11/20 General Maintenance]] – environment, box, clock adjustment, memory adjustments, diagnostics
* [[PDP-11/20 Troubleshooting Guide]] – console lamps, power faults, power-fail, MM11-E chart
* [[PDP-11/20 Power Supply Service]] – H720 circuit, protection, parts

== References ==
<references>
<ref name="sm">Digital Equipment Corporation, ''PDP-11/20 System Manual'', DEC-11-HR1B-D, title page, printing history, contents and section 1.1. Source: [https://bitsavers.org/pdf/dec/pdp11/1120/1120_SystemManual.pdf bitsavers.org].</ref>
<ref name="ka">Digital Equipment Corporation, ''KA11 Processor Manual'', DEC-11-HR2B-D, title page, contents and chapter 5. Source: [https://bitsavers.org/pdf/dec/pdp11/1120/KA11_ProcessorMan.pdf bitsavers.org].</ref>
<ref name="mm">Digital Equipment Corporation, ''MM11-E Core Memory Manual'', DEC-11-HR3A-D, title page, contents and chapter 3. Source: [https://bitsavers.org/pdf/dec/pdp11/memory/MM11-E/MM11-E_CoreMemoryManual.pdf bitsavers.org].</ref>
<ref name="h720">Digital Equipment Corporation, ''H720 Power Supply and Mounting Box Manual'', DEC-11-HR5B-D, title page and contents. Source: [https://bitsavers.org/pdf/dec/pdp11/pwrSupply/H720_PowerSupplyMan.pdf bitsavers.org].</ref>
<ref name="drw">Digital Equipment Corporation, ''H720 Power Supply and Mounting Box Engineering Drawings'', title page and drawing index. Source: [https://bitsavers.org/pdf/dec/pdp11/pwrSupply/H720_EngrDrws.pdf bitsavers.org].</ref>
<ref name="pl">Digital Equipment Corporation, PDP-11/20 price list, 1 November 1970. Source: [https://bitsavers.org/pdf/dec/pdp11/1120/PDP11-20_Price_List_19701101.pdf bitsavers.org].</ref>
<ref name="bits">Bitsavers directories [https://bitsavers.org/pdf/dec/pdp11/1120/ pdf/dec/pdp11/1120/], [https://bitsavers.org/pdf/dec/pdp11/memory/ pdf/dec/pdp11/memory/] and [https://bitsavers.org/pdf/dec/pdp11/pwrSupply/ pdf/dec/pdp11/pwrSupply/], retrieved 2 October 2026.</ref>
</references>

[[Category:Digital Equipment Corporation]]
[[Category:Service Manuals]]