Apple ImageWriter Troubleshooting Guide
Fault finding for the Apple ImageWriter and the Apple Dot Matrix Printer, taken from the symptom tables in Apple's Technical Procedures for the two printers. Apple notes that the ImageWriter's flow of information during the self-test is the same for the Dot Matrix Printer, the parallel version.[1][2] For the Apple ImageWriter II see Apple ImageWriter II Troubleshooting Guide.
Before you start
[edit | edit source]- Run the self-test before connecting the printer to a computer: with a new ribbon and a single sheet loaded, hold the form feed switch (T.O.F. on the Dot Matrix Printer) and switch on. The printer prints lines of characters until it is switched off. If the test does not run properly, where it stops tells you which module to look at.[1][2]
- Before swapping any module, check the ribbon cartridge and the mechanical adjustments; Apple notes that with printers the module-swapping method alone "can prove very frustrating".[1]
- The ImageWriter will not print with the carrier cover removed.[1]
- Apple tested the ImageWriter with the Apple II Peripherals Diskette, described in its Multi-Product Diagnostics Technical Procedures.[1]
What happens during the self-test
[edit | edit source]Apple's flow-of-information appendix describes the order of events, which helps to place a fault:[1]
- Mains enters at the power inlet on the rear and passes through the filter, which reduces radio-frequency interference.
- The transformer reduces the 120 V supply to 40 V.
- The power supply area of the CPU PC board breaks the 40 V down further and feeds the CPU area, which runs its start-up sequence.
- The carrier motor moves the carrier assembly to the left side of the platen.
- When the form feed switch is released the CPU starts the self-test.
- The CPU sends the print data to the head assembly connector under the carrier, which fires the print head.
Symptom table
[edit | edit source]| Symptom | Checks, in Apple's order | Parts to replace, in Apple's order | Dot Matrix Printer |
|---|---|---|---|
| Power lamp not lit | Power switched on and cord plugged in. Check the power fuse at the back; if it is burned out, replace it and power on again. Swap the power cord. Check that the small screw holder under the screw fixing the printer cable to the logic board is in place: if it has dropped free it may be shorting pins on the logic board. Check the three fuses on the CPU board. | If the rear fuse blows a second time: CPU PC board, carrier motor, transformer. If the CPU board fuses blow again: power switch, carrier motor, transformer. | If the rear fuse blows again: regulator transistor, CPU PC board, carrier motor, transformer. If the fuse is good: power switch, then carrier motor and transformer. |
| Power lamp on but printer will not print | Top cover seated properly (close it, press SEL and try the self-test). PE lamp lit: reload paper. Connectors between carrier, carrier motor and CPU PC board; dot head connector cable lying flat under the carrier. Screw holder in place. | CPU PC board, carrier motor | CPU PC board, carrier motor, transistor assembly |
| Passes self-test but will not print under computer control | Computer powered on and initialised. SEL light on; if it prints with the light off, replace the switch panel. Interface cable secure at both ends. Configuration switches on the printer and interface card set as in the user's manual or the Peripheral Interface Guide. | Apple interface cable, CPU PC board, carrier drive transistor assembly, carrier motor | Also rule out a software problem; then CPU PC board |
| Dots missing | Dot head in place and not clogged; dot head connector plugged into the CPU PC board; impression control lever pushed fully forward for a single sheet. | Dot head, CPU PC board | Check the gap adjustment lever instead of the impression lever |
| Printing too light or intensity varies | Impression lever fully forward for a single sheet. New ribbon cartridge. Ribbon wire tension. Adjust VR2 (IMPRES), under the clear plastic sheet over the configuration switches, for best density. | Ribbon cassette, dot head, CPU PC board | Same, checking the ribbon for age, tears, fraying or twisting |
| Horizontal spacing irregular | Carrier wire strung properly and within its tension specification. | Carrier wire, carrier drive transistor assembly, carrier motor, CPU PC board | Carrier wire, carrier motor, CPU PC board |
| Characters do not line up vertically in columns | Adjust VR1 (ALIGN), under the clear plastic sheet, for best vertical alignment. | CPU PC board | VR1 only |
| Erratic carrier motion or burning smell | Carrier motor, carrier drive transistor assembly, CPU PC board | Same order; Apple also lists a carrier that shakes or moves slowly | |
| Hexadecimal data printed | Switch the printer off and on (the select button was pressed during power-up). | ||
| Ribbon does not wind properly, light print at times | Replace the ribbon cartridge. Check the springs under the carriage mount plate: the spring with the greater tension goes under the ratchet "B" gear (see the parts list). | Change arm gear; if that fails, another change arm gear | |
| Grinding noise but prints correctly, often after a new carrier motor | Loosen the motor clamp screws and the screws holding the motor to the case, cross-tighten the motor screws until you feel slight resistance, then tighten the clamp screws. Repeat if needed. Do not over-tighten; if you have, replace the eight rubber grommets and cross-tighten again. | ||
| Carrier assembly grinds on power-up | Carrier motor transistors (with the mica insulators and screw insulators in place), CPU PC board | ||
| R7 on the Super Serial Card blows | Carrier motor transistors, with the mica and screw insulators in place | ||
| 5 A fuse on the CPU board blows when connected to a Super Serial Card | Fuse and print head | ||
| No line feed, carriage movement or dot firing because the 5 A fuse has blown, and a new fuse blows during the self-test | A stepper motor winding has shorted. Check both motors as below. | Line feed or carriage stepper motor; if both measure correctly, the main logic board |
Fuses
[edit | edit source]The rear power fuse is 2 A on Apple's main logic board schematic, 050-0089-A. The three fuses on the CPU board are FU1 and FU2, both 3 A, ahead of the bridge rectifier for the logic supplies, including the +5 V regulator, and FU3, 5 A, ahead of the rectifier for the VM supply that drives the dot head and the carriage and line feed motors. A blown FU3 therefore stops line feed, carriage movement and dot firing together, as in the last row of the table above.[3]
Stepper motor resistances
[edit | edit source]Apple's April 1991 addition to the ImageWriter symptom table gives these checks, made with the logic board removed and the motor connector unplugged:[1]
| Motor | Connector | Pins measured | Resistance, approximately |
|---|---|---|---|
| Line feed stepper motor | CN1 | 6 to 2, 6 to 4, 5 to 1, 5 to 3 | 65 Ω |
| Carriage stepper motor | CN3 | 6 to 2, 6 to 4, 5 to 1, 5 to 3 | 10 Ω |
Replace any motor that reads outside this; if both are within it, replace the main logic board.[1]
Adjustments referred to above
[edit | edit source]The print head gap and carrier wire tension procedures, and Apple's maintenance schedule, are on Apple ImageWriter General Maintenance. The full take-apart procedures are in Section 2 of each Technical Procedures manual; see Apple ImageWriter Documentation and Apple Dot Matrix Printer Documentation.
Related pages
[edit | edit source]References
[edit | edit source]- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 Apple Computer, ImageWriter Technical Procedures, in Apple Service Technical Procedures, Cross Family Peripherals, Volume Two (PN 072-0230, November 1991), hosted as File:Apple Service Technical Procedures Cross Family Peripherals Volume Two Nov 1991.pdf. Section 3, Troubleshooting: symptom table pp. 3.2-3.7 (rev. Nov 86, Jul 86 and Apr 91; PDF pp. 61-66); Appendix 3A, Flow of Information, pp. 3A.1-3A.3 (Jul 86; PDF pp. 68-70).
- ↑ 2.0 2.1 2.2 Apple Computer, Dot Matrix Printer Technical Procedures, hosted as File:Apple Dot Matrix Printer Technical Procedures.pdf. Self-test p. 1.7; symptom table pp. 3.2-3.4 (rev. Nov 82 and Feb 86).
- ↑ Apple Computer, Schematic, Main Logic Board, ImageWriter, drawing 050-0089-A, sheet 2 (power supply, dot head and motor drivers), hosted as File:Apple ImageWriter Main Logic Board Schematic 050-0089-A.pdf.