HP LaserJet 4

How to Identify and Fix Common Problems ?

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Faulty power cords and connections are an uncommon but possible cause of a printer not turning on. Before suspecting a cord failure, ensure that there is power to the wall outlet and there are no conditions preventing the printer from turning on. Testing by substitution can confirm if a cord connection is the problem.
Turn on the printer

Connect the power cord between the printer and a grounded AC outlet. Move the power switch on the lower-right bottom of the printer into the On position, and then press and release the On/off button on the front of the printer.

The printer could be dirty. Solution: Arrange to have your printer cleaned. The toner cartridge may be nearly empty. Solution: Replace the toner cartridge.
Printer sleep mode

Check that the printer does not have sleep mode enabled: Go to Control Panel > Devices and Printers. Right-click the printer in question, then select Printer Preferences. Look for an option to disable sleep or time-out mode.

A component found in electrostatic printers, laser printers, and xerographic printers and photocopiers. The fuser unit is used to permanently bond toner to a substrate by applying heat and pressure. A fuser unit is made up of two rollers; one to apply heat and one to apply pressure.
The fuse protects your printer from short circuits and power overload. It is placed between the power outlet and the switch on the left side of the printer. If your machine does not start after pressing the power switch, at first you should check if the power cable is connected to a power source.
Press the Power button to turn on the printer. Wait for 60 seconds before continuing.
You must press the power button to turn the printer back on.
This is due to the energy saving setting in the HP printer configuration, Auto Off after sleep. This setting must be disabled when there is any USB device connected to the printer, otherwise it wakes the printer from sleep mode after few minutes.
With the AC adapter unplugged, press and hold the power button for approximately 15 seconds. Reconnect the AC adapter, and then turn on the computer.
If the USB cable that connects your printer to your computer becomes loose or damaged, the two will not be able to communicate properly. Without this communication, your printer remains asleep. If possible, test the cable with another USB device.
Battery Troubles:

If your HP laptop has a removable battery, remove it and reinsert it after a few seconds. Sometimes, a faulty connection can cause the power light to blink. If you can access a spare battery, try swapping it to see if the issue persists.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

LaserJet 4 won't Power Up
ANSWER : I haven’t seen that particular behavior on that model. It either works or it doesn’t. My first choice would be the power supply.

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HP LaserJet 4

Laser Jet 4700
ANSWER : This is the most confusing post ever posted on this forum. No way you can be helped.

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HP LaserJet 4

No lights, no action despite power
ANSWER : Read this forum thread. It contains several solutions to the problem. http://fixyourownprinter.com/posts/4253

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HP LaserJet 4

HP laser jet 3015 "Upgrade Error Call HP Support"
ANSWER : rgtr

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HP LaserJet 4

Dell Laser MFP 1600n constant paper jam
ANSWER : I’m having a similar issue, checked you resolution and found the little grey piece seems to be in place and able to rock back and forth. When I send a job to the printer it sounds like it is trying to pick up the paper then I get the ‘Jam 0’ error. Any ideas ?

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HP LaserJet 4

Suggestions for previous generation of HP color laser jets?
ANSWER : You can just replace the drum wiper blades. http://www.uninetimaging.com/c/539/hp-8500-8550-ep-82

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HP LaserJet 4

HP Laser Jet 4250 13.01.00 Jam in Tray 2
ANSWER : did you check if there’s multiple feeding while pulling papers

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HP LaserJet 4

C1660w black printing light
ANSWER : Have someone fixed this? I have the same problem. Please help.

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HP LaserJet 4