Canon Pixma MP780 / MP750 Service Manual (P/N HY8-23A0-020)

• 511 PDF pages across nine Canon publications: PIXMA MP750/MP780 Service Manual, P/N HY8-13A3-000, Revision 0 — 132 pages; G3/G4 Facsimile Error Code List, P/N HY8-23A0-020, Revision 2 — 312 pages; Parts Catalog — 8 pages; Quick Start Guide, P/N HT7-0030-000-V.2.0 — 49 pages; Easy Setup Instructions, P/N HT7-0029-000-V.1.0 — 2 pages; MP750 and MP780 specification sheets — 2 pages each; and MP750/MP780 Product Service Details — 2 pages each.
• Covers the PIXMA MP750 and MP780 printer, scanner, copier, ADF, paper-feed, carriage, ink, and control-board systems, with MP780-only fax, NCU, modem, service-report, and communication-diagnostic sections clearly identified.
• Documents service-part replacement, flexible-cable and harness routing, paper-feed motor adjustment, carriage-shaft gear phasing, lift-cam and solenoid positioning, white-sheet installation, lubrication points, waste-ink counter setup, and post-repair checks.
• Includes service-switch programming, user-data and service-data flowcharts, Test Mode and Factory Mode, operation-panel and print tests, ADF/scanner/sensor checks, MP780 modem tests, EEPROM reports, SPCNT flash-ROM updating, and CD-R calibration for applicable 230V machines.
• Adds MP780 fax troubleshooting for line and compatibility problems, service activity reports, system data and dump lists, plus Canon user/service error-code tables and G3/G4 protocol references for ECM, V.8/V.34, expected signals, FIF fields, maker codes, and G4 channel procedures.
• Supplies exploded parts views and part numbers for the scanner and ADF, SPCNT/NCU and relay boards, print/ASF and ink-absorber assemblies, sheet-feed and power-supply units, carriage and motors, purge/platen components, and paper-feed rollers.
• Supporting documents cover control identification, document and paper handling, copying, direct camera printing, MP780 fax setup and operation, ink-tank and print-head maintenance, common error indications, major service parts, and page-count access.

Model and Publication Coverage

The primary repair manual is Canon’s PIXMA MP750/MP780 Service Manual, Revision 0, issued in November 2004. It identifies MP750 product codes H12-4562, -4563, -4564, -4565, -4566, and -4568, along with MP780 codes H12-4582 through -4589 and H12-4597 for the listed 120V and 230V regional configurations.

The model distinction matters. The MP780 is the fax-equipped machine; the MP750 shares the print, scan, copy, ADF, paper-feed, carriage, and service-mode coverage but does not use the MP780 fax/NCU sections. The separate G3/G4 Facsimile Error Code List was issued in September 2001 as a general Canon facsimile reference. It is not an MP750/MP780-specific repair manual, and its G4/ISDN material is broader than the Super G3 fax system fitted to the MP780. The MP780 service manual refers technicians to this separate list for communication codes outside its model-specific tables.

Repair, Adjustment, and Factory Diagnostics

Repair coverage includes the paper-feed motor and belt position, carriage-shaft gear phase, lift-cam timing, solenoid spring orientation, carriage-shaft clip location, scanner white-sheet placement, specified grease points, and waste-ink counter registration after board or absorber work. The special-tool table identifies MOLYKOTE HP300, P/N CK-8012-000, and FLOIL KG-107A, P/N QY9-0057-000, with their intended gear, shaft-lift, carriage, and carriage-shaft applications.

Test and factory sections show the available system, scanner, printer, modem, sensor, operation-panel, CCD, carriage-gear, and CD-R functions. Verification material includes service test prints, EEPROM information, MP780 system data lists, system dump lists, and sending/receiving service activity reports. These reports expose communication history, service codes, protocol data, counters, and board information used after repair.

Several shop-specific cautions are documented. Improper flexible-cable or harness routing can break conductors and create an ignition or smoke hazard. Residual capacitor charge can damage the SPCNT board, while loosening the wrong red chassis screws disturbs the factory carriage-shaft position. After SPCNT board replacement or an ALL-clear, the wrong power-cycle method can leave service data unwritten.

Fax Error-Code and Communication Reference

The 312-page error-code volume separates user codes from service codes and marks each entry for transmission, reception, or both. Tables pair the fault description with possible causes and remedy logic. Coverage ranges from document-feed, memory, polling, paper, and dialing faults to phase synchronization, carrier detection, modem-speed compatibility, ECM/V.34 procedure errors, and model-dependent thermal-head, stepping-motor, backup-memory, and control-board faults.

Its appendix adds the three-point communication isolation flowchart; G3, ECM, and V.8/V.34 control diagrams; transmitted, received, and expected signal definitions; FIF bit-field tables; maker codes; and the protocol-recording connection diagram. G4 material covers channel D and channel B control procedures and major layer signals, followed by a conversion table for alternate error-code formats. Definitions also cover transmission-level adjustment, the NL equalizer, page timing, T0/T1/T5 timers, and echo-related service settings.

Parts Information and Scope Limits

Canon states that the service manual alone does not provide enough detail for full disassembly and reassembly and directs the technician to the separate Parts Catalog. That 8-page catalog is included and contains thirteen exploded figure groups with component callouts and part numbers, but it is not a step-by-step teardown sequence.

Electrical-schematic scope: the service-manual PDF moves from the Part 3 appendix divider directly to specification page 3-5. The TOC-listed Wiring Diagram, Circuit Diagram, NCU Circuit Diagrams 1 and 2, and Relay Circuit Diagram pages 3-1 through 3-4 are not included. Board photographs, connector routing, cable-placement views, service-data charts, and exploded parts views remain available, but this set is not a complete electrical schematic package.