1996 HP DesignJet 700/750C/750C Plus/755CM Service Manual (P/N C4705-90000)

This 287-page PDF reproduces the August 1996 second edition of Hewlett-Packard's service publication for the HP DesignJet 700, 750C, 750C Plus, and 755CM plotters/printers, identified by HP Internal Order Number C4705-90000. Coverage is tied to the actual machine codes: C4705A (D/A1) and C4706A (E/A0) DesignJet 700; C3195A (D/A1) and C3196A (E/A0) 750C; C4708A (D/A1) and C4709A (E/A0) 750C Plus; and the E/A0-only C3198A/C3198B 755CM. Model tables distinguish the monochrome DesignJet 700 from the color machines, the 750C from the 750C Plus, and the C3198A/C3198B builds by memory and resolution capability. HP states that the procedures are intended for HP-certified service personnel, making this a technician-level repair reference rather than an operator guide.

• Maps the carriage/Y-axis and media/X-axis systems, following motion from the drive motors, belt and tensioner, encoder strip, and drive roller through the cutter, bail, overdrive, pinch-arm, and roll-feed assemblies.
• Provides 39 illustrated removal and reinstallation procedures covering electronics PCAs and memory, the carriage and drive belt, trailing cable, motion motors and sensors, the service station and primer, and roll-feed/media-path hardware.
• Documents 32 built-in Service Tests covering EEROM, MIO and PCA communication, carriage motion, thermal control, pen continuity and identification, nozzles and drop detection, alignment, cutter and bail operation, media handling, encoders, and front-panel inputs.
• Links repair work to the required calibration path through a calibration decision table and dedicated drop-detect, line-sensor, and accuracy-calibration procedures, including the components and EEROM conditions that make recalibration necessary.
• Diagnoses output defects with three service plots—the CAD 2-D Monochrome Plot, CAD Color Diagnostic Plot, and Area-Fill Diagnostic Plot—and identifies causes of banding, cockle, coalescence, bleeding, feathering, black migration, and halo effects.
• Supplies exploded parts views and HP part-number tables with model- and size-specific distinctions. Named illustrations include the Electronics Block Diagram, Electronics Enclosure, Carriage-Axis, Service Station and Primer Assembly, Media Entry Path, and Bail and Overdrive.

Functional Theory and Fault Isolation

The functional chapters explain how host communications, the main and servo processors, stepper motors, cartridge firing, pulse-width-modulated controls, and the line, drop, temperature, linear-encoder, window, pinch-wheel, media, and primer-cam sensors interact. PCA-level coverage describes the main, carriage, front-panel, line-sensor, drop-sensor, and power-supply boards. Troubleshooting pairs worded front-panel messages and six-digit hexadecimal system errors with corrective actions, the internal Service Tests, PC-based diagnostics, the service configuration plot, and EEROM maps. This gives a repair technician a structured route from symptom to subsystem without reducing the material to a generic maintenance checklist.

Repair Procedures, Maintenance, and Service History

The mechanical chapter identifies the required Torx and Pozidriv drivers, nut drivers, spring hook, 10X magnifier, and loopback connector; the latter is listed as HP Part Number 07440-60302. Preventive-maintenance coverage includes drive-roller cleaning, service-station and spittoon care, encoder-strip and carriage-axis work, maintenance-plot and cycle counters, preventive-maintenance kits, and counter reset after repair. Product-history sections record firmware revisions, known issues, and service-note remedies involving the entry platen, paper advance, aerosol-related servo shutdown, leg stability, mark-encoder changes, pen alignment, and fan-airflow deflection.

The paper-advance and mark-encoder service notes identify C3195A serials ESA0000000–ESA5B05350, C3196A serials ESA0000000–ESA5B20304, and C3198A serials ESA0000000–ESA5B02306. A separate fan-deflector update is limited to E-size C3196A and C3198A units in range ESA0000000–ESA4508541.

The encoder-strip section flags the strip as fragile and explains that damage during removal can compromise the carriage-position reference. The pinch-arm procedure warns that overtightening the cam-journal screw can break the journal, let the bar cam enter the sideplate hole, and bind the lift lever.

Installation Data and Scope

Site-planning and installation sections cover unpacking and repacking, optional legs and media-bin installation, interface and front-panel configuration, power-on checks, environmental limits, dimensions, and handling data. The self-adjusting supply is specified for 90–264 V AC input with 140 W maximum consumption; listed weights are 32 kg (71 lb) for D/A1 units and 42 kg (93 lb) for E/A0 units. Electrical repair carries shock and ESD risks: disconnect mains power, use the required protective-earth connection, and follow antistatic handling practices before opening the electronics enclosure. Day-to-day operating instructions are assigned to the separate user and quick-reference guides; this manual concentrates on test, calibration, service, parts identification, and repair.