High Voltage Error; Thermistor Open Error; Front Panel Cycling Between Ready And Warming Up; Erratic Printer Behavior - Tektronix Z740/N - Phaser 740 Color Laser Printer Service Manual

High voltage error

1. Replace the high voltage board.
2.
Inspect the high-voltage wiring.
3. Replace the imaging unit and check the printer for proper operation.
4. Sequentially replace each toner cartridge and check the printer for proper
operation.
5.
Ensure that excessive conductive grease has not migrated and shorted a
high-voltage contact to ground on the second bias transfer roller.

Thermistor open error

1.
Check the connector CN27 on the engine control board.
2.
Ensure a 110 volt fuser has not been installed in a 220 volt printer; it will
damage the power supply thermistor and require the power supply be
replaced.
3. Replace the fuser.
4.
Replace the engine control board.

Front panel cycling between READY and WARMING UP

1. Make sure that the fuser, imaging unit, and toner cartridges are well seated.
2.
Invoke a test print from the Front Panel to try to get an error message to be
displayed that may be present but, is masked by the front panel cycling
between READY and WARMING UP.
3. Make sure all connectors to the circuit boards are well seated and make sure
that the screws holding the boards's in place are tight.

Erratic printer behavior

1.
Check the amount of RAM installed in the printer. While more than
192 Mbytes of RAM can be physically installed on the image processor
board, it can electrically support no more than 192 Mbytes. Unreliable
printer operation can otherwise result.

Installed RAM not recognized

1.
Upon power-up, the image processor checks each DIMM for information
such as data width, clock delay, number of address columns and row,
refresh rate and more. If the DIMM does not meets the required
specifications it will be ignored; no error message will be reported.
46 Phaser 740 Color Printer