How to fix LSU error HP CLJ-cp2020 printer

LSU unit has components indispensable in laser printers, If has not LSU unit then the printer does not print. In this article, I will introduction to you the function, principle of operation and some error of LSU unit.

I. The function of the LSU (laser scanning unit) block printers

– Create laser emission intensity changes according to the gray level of each pixel (pixel)
– Shoots laser spread over the length of the drum (line by line of image)
LSU unit have structure as follows:

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LSU unit HP CLJ-cp2020 printer

Input:
– Receive the signal “Start” from the control circuit.
– Status signals (cover) of switches located on the LSU unit (that may or not).
– Voltage represents gray level of each pixel (real-time) analog format from data circuits.
– The signals notices resolution of printed page from data circuit sent to.
– Power Supply
Output:
– Safety Signal(from IC MDA) LSU unit returns control circuit.
– The lasers spread evenly along the length of the drum (line by line of image)

II. Principle of operation of LSU unit

– After have finished processing the data from the PC sent to. The data circuit will notify to the controller board to preparing to create
– Control circuit ordered.
* Transfer data to show gray level of each pixel into optical circuits.
* Allow active optical circuit.
– At that time, IC MDA of optical circuit will be controller motor deflection gleam (with a constant rate, depending of the machine type or print resolution).
– At the same time, IC MDA also amplifier voltage of pixel and taken to diode laser to make active diode and the laser emission. Thus, the intensity of the laser beam is constantly changing (at weak / at strong) depends on the voltage of each pixel.
– You should noticed, internalize of the laser diode have copper circle front of the laser. This is round convergence (convergence of static electricity), the voltage on the ringe will determines for convergence of laser emission from it are large or small. Through adjusting the resolution of the print (dpi – dot per inch)
– The laser light emitted from the laser diode passes through converging lens to shrink (the diameter of the laser beam) will determine great extent / small of pixels. The principle of convergence by static electricity cycle like the principle of convergence in the grid Focus in lights CRT.
– The laser light through the glass filter to ensure remove all interference may distort the frequency of the laser to beam deflection motor.
– Beam deflection motor rotating very high speed (you can hear a slight hissing noise when it starts, its rotational speed also contributes to determine print resolution). The axis of beam deflection motor shaft fitted with 1 piece of square steel (about 10mmx10mmx1mm) white bar. Lasers impact it, with the rotation speed of the steel pieces are very high when it break angle (refraction) of each beam (at one time, each ray representing 1 pixel) make each beam shot in the spectacles refractor.
– Glass refractor is piece of transparent plastic have duty break angle and laser beam to them fired up reflector. The axis of beam deflection motor shaft fitted with 1 piece of square steel (about 10mmx10mmx1mm) white ball. Lasers impact it, with the rotation speed of the steel pieces are very high when it break angle (refraction) of each beam (at one time, each ray representing 1 pixel) make each beam shot in the spectacles refractor.
– Glass refractor is piece of transparent plastic have duty break angle and laser beam to them fired up reflector.
– Mirror is parallel with glass refractor and deflection of angle about 45 degrees, making the task of laser shoot on the OPC drum. The rays go through the empty cavity openings. If you remove the bottom of LSU unit you will see have 1 slit (size about 5mmx200mm).
So: It is possible to draw some comments
– The more laser beam small, the more size of pixels small (and vice versa). This issue is adjusted through change control cycle convergence.
– Laser intensity dependent operating voltage of the laser diode. This is very important, it directly affects the pierced / pale prints.

III. Some error of LSU unit of HP CLJ-cp2020 printer

1. HP CLJ-cp2020 printer does not print

Phenomenon: the printer received print commands, data flashing lights, the gears has activity (the gear wheel make noise) about a few seconds and then stop and do not feed the paper. And then report for user: “Scanner error” or “LSU error” …
This error is caused by a feedback signal from the optical IC MDA in LSU unit induced. Normally, when the operation command received from the controller IC MDA will perform three actions:
– Send feedback signal to the controller, good condition reports.
– Power supply for beam deflection motor rotating (you will hear a slight hiss, piece)
– Power supply for laser diode and convergence rings.
Error location: In this case, 99% is due to IC MDA failure, outside circuit of the IC is extremely simple, fewer components and virtually no damage.
FIX: Replace IC MDA, right name.

2. HP CLJ-cp2020 printer printout light image

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How to fix LSU unit printer HP CLJ-cp2020 printer error (light image)

With conditions: toner powder has best quality, good OPC drum, good high pressure.
This phenomenon is due to circuit MD (monitor diode) mission control emission intensity of the laser diode leads to poor performance laser intensity is too much degrade static on the drum, causing blurred prints.
FIX: Open the LSU unit cover and then adjust rheostat MD (next to laser diode) about 1/8 of the left circle and print test page. If not met, continue to adjust.
Note: Before adjust, need to put on a little oil of sewing machine on the surface of rheostat for lubrication, avoid coal face in the back side of rheostat cracked or broken.

3. HP CLJ-cp2020 printer printout black/white spot image

 

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How to fix LSU unit HP CLJ-cp2020 error (black/white spot)

With conditions: toner powder has best quality, good OPC drum, good high pressure.
This phenomenon is due to system and beam deflection of LSU unit caused and The main cause is LSU unit has dirty
FIX: You should clean the LSU system
– Clean the white metal bar (10mmx10mmx1mm) mounted on the beam deflection motor.
– Clean the glass refraction.
– Clean the glass reflectors
If these objects has moldy, dirty then wash with “dishwashing liquid” and a soft brush. Then wipe dry with a soft cloth. Make sure them drying, not washing with chemicals (such as alcohol, acetone …)

4. HP CLJ-cp2020 printer printout black or dark image

This phenomenon is due to laser rays be lost or laser emission intensity is too weak. Laser printers use to laser rays white (other than CD / DVD use red-laser or blue) so can not check out with the naked eye.
FIX:
– Adjust Potentiometer MD to checking (to the right), each adjusted about 1/8 of the left circle.
– Check voltage 5V (+), this is static voltage for the diode laser. If it lost, you should checking converse to the head of cable of LSU unit. The line typically have 1 fuse resistance (0.47 Ω) and 1 filter capacitor (several tens of nF, depending on the printer) behind the resistance. Resistance can cut, filter capacitors can short, replace (right values​​).
– If the voltage is 5V, adjustment rheostat MD, If not be solve, replace the laser diode (this cause have probability occur very low, a few%).

5. HP CLJ-cp2020 printer printout character, the lines (curved, straight) have blurry two sides.

This phenomenon due to laser rays does not bunched (convergence) or poor convergence, therefore the pixel in the OPC drum has increased size
FIX:
Change Voltage of the static convergence ring by rheostat on the optical circuit. This usually variable resistor symbol (FC, ​​Vfc) located near dioe laser (farther MD a little ). After each adjustment, test print until reaching definition out loud.
More details, you view in “HP CLJ-CP2020 Service Repair Manual”.
You can pay it at the following:

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