Learn these six components that make up the Electronic Paper Control Assemblies, and you are on your way to graduating as a real HP laser printer technician.
The one thing that is constant in our world is change. But when it comes to electronics, the good news is that inside the printer, the basic electronic components remain unchanged.
The electronics perform the same two roles that all electronic systems do‘ they control and process data and they distribute energy. Six key components are essentially the same across all printers‘ the AC power supply, the DC power supply, the high voltage power supply, the scanner, the DC Controller, and the Formatter.
That in a nutshell, is the printer's block diagram. Learn these six, and you are on your way to graduating as a real tech.
You may think that the DC Controller does all the work in the printer, but in many cases it just relays messages. The DC Controller is the brain of the machine. It receives all of the inputs, and determines what the printer should do. If there is a jam, it will
shut down the printer until the jam condition is cleared.
Now you may say, what is an engine control board, then? Well, an engine control board (also referred to as the ECU) is the combination of the AC power supply, !C power supply, DC Controller (DCC) and in many models the High Voltage Power Supply (HVPS) as well, sort of an all-in-one assembly.
The service manual's theory of operation section will show you what assemblies are included in the ECU. If the printer does not contain the AC power supply or a DC power supply, these are usually contained in an assembly called the Low voltage power supply (LVPS).
1) The HP Laser Printer AC Power Supply
The AC power supply is responsible for doing two things. First, it supplies the fuser with the power to create heat. Once inside the printer, the majority of the power flows to the fuser. The AC power supply is also responsible for supplying the DC power supply with a clean power source. The AC power supply has a fuse right after the power goes from the cord to the unit.
This fuse is there to ensure that if a short circuit condition occurs that it prevents the unit from burning the building down. If this fuse is open or blown be sure to replace it with the same current rating. If the fuse opens again, you have a problem in the machine that requires replacement of a module.
2) The HP Laser Printer DC Power Supply
From the AC power supply, the power goes to the DC power module. You may be wondering why the printer requires an AC and DC power supply. The reason is that the power comes into the printer as Alternating Current (DC power). Most electronics and semiconductors use direct Current (AC power) as a power source.
This is the same way a computer power supply works. The DC power supply is responsible for turning the 120 volt AC into DC voltages (typical voltages are 24v 5v, and 3.3v ). These voltages are regulated. With an unregulated power supply, when the current draw increases, the voltage decreases.
A regulated power supply has a constant output, even if the current draw changes or the input voltage changes. There will come a point when the unit will go into protect mode (such as an over current, or an input voltage too low situation). Basically, this will shut the unit off until the problem corrects itself. If one of these voltages is missing, the unit will not operate properly.
The 24 volt line is used for motors, fans, and clutches / solenoids. The 5 volt line is used for sensors and the logic. The 3.3 volt line is used for logic. The DC power supply feeds voltage to the HVPS , DC Controller, scanner and formatter.
3) The HP Laser Printer High Voltage Power Supply (HVPS)
The HVPS takes the DC voltage and turns it into a high voltage source of AC and DC power. This voltage gets supplied to the toner cartridge, transfer roller and fuser. It's used in the toner cartridge to clean and condition the drum. The transfer roller uses another voltage to transfer the toner from the drum to the paper.
The fuser uses a voltage to prevent toner adhesion to the rollers in some models. One of the voltages is fed through the toner hopper and back to the HVPS to inform the machine that the toner cartridge is present or low on toner. If the HVPS is not functioning properly, you will have an imaging problem or false toner condition.
In some cases all signs will point to the HVPS as the culprit when in fact it is a bad contact between the HVPS and the toner cartridge or transfer roller. Corrosion and foreign particles in the machine can cause intermittent problems with the HVPS.
4) The HP Laser Printer Scanner
The scanner is responsible for writing an image to the photo conductive drum. The scanner consists of two components‘ the scanner motor and a laser PCA. The laser pulses very rapidly while the scanner motor turns. This motor has a mirror to spread the beam across the paper path.
This assembly also has a feedback circuit to inform the DC Controller that the scanner beam is present when operating. Foreign materials such as dust, dirt, and toner can build up on the mirrors and cause a light or blurry print. This assembly has a shutter on it to prevent the beam from exiting the scanner when the top cover is open. If the scanner is not installed properly and the shutter is closed, you will, in most cases, get a blank page with no errors
5) The HP Laser Printer DC Controller
The DC Controller is the brain of the printer. All functions in the printer report to the controller. The controller does all the timing calculations in its microprocessor. Sensors all report here. If a connector is not plugged into the controller, you can see where this would cause problems.
6) The HP Laser Printer Formatter
The formatter is responsible for a few things. Its main function is to interpret data from external inputs and convert them to a language the !CC can understand. The formatter interfaces with network cards (EIO, MIO), internal printer hard disks, ROM, RAM, firmware, and font DIMMS. In some of the newer printers, the formatter can send signals back to the computer to inform it of any important information to the user (such as a paper jam or out of paper condition).
The HP printer formatter is responsible for relaying printer status information to the control panel, along with monitoring the input from the control panel. In most machines, the printer can still perform basic functions without having the printer formatter attached to the machine. This is done by using the engine test button on the machine.
While inventors have made some huge strides and big improvements to printer models over the past two decades, the basic flow diagram we have described has not changed. Since we sold our first part, the component logic remains the same. This holds true even for MFPs (with the addition of the devices that make them multifunction). By understanding how the electronic components work, you will troubleshoot faster, reduce frustration and save money when doing repairs.
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