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.