HP DesignJet 1050C / 1055CM Factory Service Manual (P/N C6071-90000)

• A 320-page PDF of HP's first-edition service manual for the original HP DesignJet 1050C (C6074A) and HP DesignJet 1055CM (C6075A) large-format printers. The stated coverage is model-specific; this edition does not identify later Plus-series product numbers.
• Built-in diagnostics cover the Electronics Module, DRAM, Trailing Cable, Carriage Assembly, EIO card, hard disk, Ink Pressure System, Scan Axis, Paper Axis, and Drop Detector, backed by continuable, non-continuable, and initialization error-code troubleshooting.
• Ink-system sections explain the HP No. 80 supplies, Ink Supply Station (ISS), Tubes System, Air Pressurization System (APS), Ink Level Sensing (ILS), Leak Detect System (LDS), printheads, and Printhead Cleaners, including tube priming, Tubes Purge, pressure-system testing, and leak fault isolation.
• Service calibration coverage includes media-advance accuracy, Line Sensor, Service Station, Roller Mark Position, Color-to-Color, Pen Alignment, Carriage Height, and EEROM calibration backup, with a matrix showing which calibrations are required after specific assemblies are disturbed or replaced.
• Removal and installation procedures cover the Electronics Module, Service Station, Drop Detector, vacuum fan, paper- and scan-axis motors, encoder strip, trailing cable, carriage and belt, cutter, ISS/APS, Tubes System, ink leak detector, platen, drive roller, paper-entry components, and pinch-wheel assembly.
• Includes model-specific parts tables and exploded assembly views, the internal Print Quality Test, preventive-maintenance guidance, the Carriage Height Tool (P/N C6071-60166), and the Carriage Interconnect Wiper used for printhead and carriage electrical-contact service.

Diagnostic and Service Overview

This manual is built around fault isolation before parts replacement. The Electronic Systems test checks the Electronics Module, memory, Trailing Cable, and Carriage Assembly as one diagnostic group, while separate tests address the EIO card, hard disk, ink-pressure hardware, scan-axis drive, paper-axis drive, and Drop Detector. HP's repair logic is direct: run the relevant test first, and do not replace an assembly that passes. It also explains failure displays, component isolation, and the required power cycle before normal operation.

The Service Configuration Print adds another layer of usable repair data. It records firmware and installed configuration, printhead and cartridge information, operating temperature and humidity, completed calibrations, maintenance history, power-on and carriage-cycle counts, the last system error, and JetDirect configuration. This helps separate mechanical and ink-system faults from configuration, consumable, environmental, or network-related problems.

Both models include a network interface, but their internal configurations differ. The 1050C is specified with 16 MB of memory and no hard disk. The 1055CM has 32 MB, a 2.1 GB hard disk, and a PostScript-ready configuration. A Printer Model Type utility is included for repair situations in which the Tubes System and Electronics Module have both been replaced.

Print-quality diagnosis goes well beyond a generic cleaning checklist. The internal test is divided into a nozzle pattern, a twelve-pattern color-alignment check, and a seven-color BEST-mode pattern for banding in dense fills. The nozzle section shows how to distinguish missing, partially firing, and misdirected nozzles; the remaining chapters trace color misalignment, media-advance banding, stepped or missing lines, smearing, scratching, cockling, head crashes, color inconsistency, and glossy-media bleed. Front-panel recovery, alignment, and service-calibration functions are tied back to the defect patterns they are intended to correct.

Repair Procedures, Calibrations, and Parts Reference

The removal and installation chapter is arranged in disassembly order, so it can support anything from a single assembly repair to a full mechanical strip-down. Procedures are illustrated and linked to the related service test and post-repair calibration requirements. The parts chapter supplies HP part numbers and exploded views for the Electronics Module, ISS/APS Assembly, Carriage Assembly, Scan-Axis Assemblies, Paper Path Assemblies, and Tubes Guide Assemblies.

Calibration content is especially useful after major repair work. The manual maps carriage, Electronics Module, paper-axis, platen, Service Station, drive-roller, and Tubes System work to the calibrations that must follow. It also documents EEROM backup after Electronics Module or Tubes System replacement. The Pen-to-Paper Spacing entry is retained only to warn that the calibration is obsolete and must not be performed.

Several repair traps are called out clearly. An incorrectly seated Trailing Cable can burn the internal fuse in the Electronics Module, so the manual includes an installation-position and continuity check before power is applied. During Carriage Height adjustment, the carriage must be moved by the belt rather than pushed directly, and the dedicated tool is used to establish clearance over the center platen. Power must not be interrupted while the EEROM is being tested or cleared because the Electronics Module can be damaged; after an EEROM clear, stored settings and calibration data must be recovered through the specified backup procedures.

This is a service and repair publication rather than an operator's guide. Routine printer use is assigned to the separate User and Quick Reference Guides. Electrical coverage is organized around functional PSU/PCA descriptions, system tests, cables, replaceable assemblies, parts views, and test data rather than a separate point-to-point wiring-diagram chapter.

The publication is written for HP-qualified service personnel. Disconnect the printer from AC power before opening it and follow the manual's grounding and ESD precautions around the Electronics Module and PCAs. Service-test mode bypasses normal initialization and disables cover-sensor protection, so moving assemblies require the same precautions used by trained printer technicians.