Hardware - Trouble Shooting

Power Supply Failure - Trouble Shooting Steps

• Did power come on? Can you hear fans turning, and drives motors spinning up, see front panel led hear any beeps? If the system case is hot (shock) pull the plug– check for ground failure and a short.
• If the power doesn't come on, check for a live power source.
• Check to make sure the correct voltage (110V/ 220V) is selected on the power supply-the small red slide switch on power supply, select the proper voltage for your country.
• If pressing your power switch doesn't immediately shut down the PC, that's normal for ATX systems. The action of the power switch is programmable and is controlled through CMOS Setup; check CMOS Setup power management settings. If the problem is that the operating system can't turn off the PC when you shut down, it's likely a bad setting in power management or a corrupted file in the operating system.
• Unconnected power switch. The power switch lead on ATX PCs, often labeled PW or PW-ON, runs from the front panel of the case to a connector block on the motherboard, it must be on the correct two posts. Read motherboard printing or documentation for proper location.
• The power supply will not operate if the power to motherboard isn't connected. Check that the 20 pin ATX power connector and any additional motherboard power connections, such as the 12V supply for P4 systems, are properly connected and seated.
• Remove the power leads to the drives to ensure that you aren't trying to power up into a short. The motherboard power must remain connected to activate the ATX power supply. The 5V on Pin 9 is always present when the power supply is plugged in. This connection supplies power to the various PC circuits that operate even when the PC is turned off, such as "Wake on Modem/LAN." Restart the PC to check for active power supply.
• The color scheme used for the voltages in the 20 pin connector holds for the other ATX standard power supply connectors, branded proprietary power supplies or make up their own color coding.
  
  
  

  ATX Version 1.2 - 20 wire motherboard connector DVM probes
  Pin 1	Pin 2	Pin 3	Pin 4	Pin 5	Pin 6	Pin 7	Pin 8	Pin 9	Pin 10
  3.3V	3.3V	Gnd	5V	Gnd	5V	Gnd	P_OK	5VSB	12V
  Oran	Oran	Blk	Red	Blk	Red	Blk	Gray	Purp	Yellow
  Oran	Blue	Blk	Green	Blk	Blk	Blk	White	Red	Red
  3.3V	-12V	Gnd	P_ON	Gnd	Gnd	Gnd	-5V	5V	5V
  Pin11	Pin12	Pin13	Pin14	Pin15	Pin16	Pin17	Pin18	Pin19	Pin 20

• Assuming your PC is connected to a monitor, the next question is, do you have a live screen? Does text or a splash screen appear? A message saying "Please connect monitor" or "No video signal detected" counts as a "No" answer in this case. If the screen is live, but you see multiple images or endless scrolling, the video adapter is providing signals that cannot be interpreted by the monitor. This usually occurs when you attach an old monitor to a new PC and the monitor doesn't support the refresh rate at the screen resolution selected in the Windows settings.
  
• If the power supply comes on but you don't get a live screen, switch off and try again,. A PC that boots on the second or third try is most likely suffering from a quick power_ok (or power_good) signal. The power_ok signal tells the motherboard that the power supply is stable, while its absence tells the motherboard to stay off to protect itself. If it requires booting twice to turn on the PC isn't an ideal situation, try buying a higher quality power supply, recommended by the motherboard manufacturer.
• Beep codes are part of the PC's Power On Self Test (POST) routine. If you don't get any beeps check for case-speaker connection or onboard piezoelectric speaker (burser) and then check for beeps again.
• If you have recently added any new components (adapters and drives) to the system, they may be overtaxing the power supply or causing a short circuit. Undo the last change you made.
• Common power supply problems unrelated to the boot process are noisy operation and unstable voltages, both of which are a reason to replace the supply
• As soon as the PC powers up, you should be able to hear the hard drive motor spin the drive and the read/write head seeking (a gentle clunking sound). If system power is coming on but the drive still isn't spinning up, check power lead seating.
• If system power isn't coming on, disconnect all drives, one at a time, and try powering up after each change. If the system powers up, you've found a faulty drive or a faulty lead from the power supply. If the system won't power up with all drives disconnected, start removing adapters, one at a time, leaving the video for last. Unplug power cord before removing each adapter, then reconnects to power up. If the system powers up, replace all adapters except the last one removed before power came on. If power on, try the last adapter too in a different slot before giving up on it.
• If an adapter prevents the system from powering up, it must be replaced.
• Remove the motherboard and check for a standoff or screw located in the wrong place or rolling loose.
• Normally, a short circuit will result in a burnt smell and a ruined motherboard, sometimes damaging components (memory, CPU, adapters) as well. If you can't locate a failed component, you need to access to a test-bed system (an inexpensive but completely functioning PC for testing questionable parts). Don't test parts in a good system, because some types of failures will cause damage to the next machine.
• If you've reached this point without getting the system to power up, you probably have a defective power supply or motherboard. Try replacing the power supply first since they're cheaper than motherboards. If the power supply or motherboard is new, they may be incompatible with one another due to poor adherence to ATX standards or support for different generations of the ATX standard.

=============================================

Motherboard Troubleshooting

1. You have live screen? At least BIOS screen.
2. Does the system power up? If the power isn't coming on, proceed to Power Supply Failure.
3. Perform the Video Failure diagnostics for a dead screen; check the power cord and the outlet.
4. Check for improper insertion of memory modules. The levers should be lowered before inserting the memory module, and should raise themselves up and lock in place when the module is correctly seated. If using multiple banks that needs to be match (type, speed).
5. Failed CPU insertion, whether it's a slot or socket CPU. If a socket CPU is a new install, remove the heat sink and CPU to visually inspect it for damage such as crushed or bent legs. Raise socket locking arm all the way before insertion, and lowered it all the way down after. If your CPU won't sit down properly in socket, either the socket is faulty or you have the wrong CPU for the motherboard!
6. All modern CPUs require an active heat sink, with a fan on top. The fan on the heat sink, must be hooked up to the correct power point on the motherboard for the BIOS to monitor its condition and turn it off and on. Check the heat sink fan; it is an indication of a working motherboard.
7. If system powers up, and hear any beeps coming from the motherboard speaker. A 3 long beeps – is for bad RAM, a repeated sequence can be RAM or video error. On beeps or no beeps, reseat the video adapter and the RAM, with attention to the locking levers.
8. Are your motherboard settings on the defaults? If CMOS setting is not correct, restore default BIOS with a jumper or switch setting. Modify CMOS settings with reference to motherboard documentation. The default settings usually put everything on auto detect and use the recommended timing for the RAM. if you're over clocking RAM, stop it, at least until you get the system running again.
9. Make sure some standoffs aren't higher than others, which can cause unacceptable stress on the motherboard. Count the standoffs, screws, and make sure that all screws are inserted.
10. If still have a "no power" situation with the motherboard running, do a quack test with known good cheap old CPU with a good heat sink fan, sometimes the motherboard may be a CPU eater. Leave all the motherboard settings on the default "Automatic" setting to avoid setting mismatches. If the heat sink fan is working, determining whether the CPU failure was due to poor heat sink contact, improper motherboard settings, or lousy power regulation from the motherboard is a guessing game.
11. If you still have a no power situation, go through the Video Failure diagnostics and Power Supply Failure diagnostics.
12. Does the system freeze on the BIOS screen? During or after memory count, while checking for drives, or "Verifying DMI Data Pool." The problem is very likely due to a conflict between the adapters or between incompatible drives sharing a bus.
13. Test system just with a power supply, motherboard, minimum RAM, CPU and heat sink, and video adapter and display. If the system no longer freezes, but complains about the lack of a boot device, now perform to disk drive Conflict Resolution.
14. Try swapping the RAM, or moving the module to other slot. If this doesn't cure the freeze-up, try some suitable known good RAM from another system. Improper RAM can be the cause of problems ranging from no-boot to intermittent lock-ups. Don't toss out the RAM you removed, you may find out later that it's actually good.
15. An overheating will cause the system to quickly lock up. Remove the existing heat sink and fan, make sure that the fan is working properly AND that the geometry of the bottom of the heat sink will bring it in full contact with the exposed CPU die or the top of the CPU package. Don't put on too much thermal grease which is only there to fill the microscopic gaps between the die surface and the heat sink. Be patient, study the mechanical connections, heat sink must fit on the particular motherboard. If any problems on heat sink or fan spin, replace it with a new active heat sink unit. CPUs may damage themselves when they overheat.

=================================================================================

Video Card Trouble Shooting

1. Assuming the system power comes up; does the monitor power come on? (Status LED on the front bezel, hear monitors power on with a gentle sound, or the sound of a CRT tube warming up). Make sure the monitor is plugged into a good outlet by testing the outlet, power cord-partial cord insertion is the most common failure for monitors with detachable cords.
2. LCD monitors are usually powered by an external transformer, which in turn is powered from a regular AC outlet. If the LCD display doesn't show any signs of life, make sure that the cords into and out of the transformer are fully seated, watch the status LED or check for live output with a DC voltmeter.
3. Check the monitor by attaching it to another working PC.
4. If you see only a single underline character blinking, usually in the top left-hand corner of the screen, there's probably a problem with initializing the video adapter. That could be caused by the adapter being improperly seated, the motherboard not initializing the adapter properly, or motherboard related failure.
5. Most new monitors will display something such as "No signal," or "Attach video signal," as long as they are healthy, and powered on. It comes even if the PC or video adapter is dead.
6. Make sure the 15 pin video signal cable (3 rows of 5 pins each) is seated squarely on the video port on the video card. The hold-down screws on either side of the connector should be screwed in all the way, but not made up too tight. If the video cable is connected correctly, remove it and inspect connector for damage.
7. Look carefully at the pins in the connector that they are not bent. Note that missing pins in a video cable are the norm, usually the monitor ID pins.
8. If you see a bent pin, try to straighten it very slowly with tweezers or fine needle nose pliers. If a pin breaks, you can buy a replacement connector and solder it on with a fine soldering iron and infinite patience.
9. Video Connector Pin out : 1-Red, 2-Green, 3-Blue, 4-Monitor ID (ID bits pins often not present), 5-Ground, 6-Red return(coax shield) , 7-Green return(coax shield) , 8-Blue Return(coax shield) , 9 No-Connection 10-Sync Ground 11-Monitor ID 12-Monitor ID 13-Horizontal-Sync 14-Vertical-Sync, 15-Monitor ID
10. Do you hear a string of beeps, different BIOS manufacturers use different beep codes to identify failures, a repeating beeps (3 or 9) is a common indicator of video card failure.
11. To start troubleshooting the video adapter, check if it's is properly seated after unplug the system power cord, reseat it. Remove the adapter holding screw, remove adapter, then reseat it in the slot, pushing down evenly, the hold-down screw back in, the screw in should not lever the front edge of the video adapter.
12. If reseating card doesn't clear up the beeps, power down and try reseating the RAM or adapter again without going all the way through the motherboard diagnostics.
13. The system lock up on the BIOS screen, then it is rarely suffer from a video failure, though a conflict between the video card and another installed adapter is still possible.
14. Did you install any new adapters immediately before the video card problem appeared? With the power disconnected, remove any other adapters, one at a time, and then reconnect power and attempt to reboot after each removal. Locking up on the BIOS screen is often due to an adapter conflict, but if removing the other adapters doesn't solve the problem, at last proceed to Motherboard, CPU and RAM Failure.
15. Do you get a live screen, or past the BIOS screen, with all the other adapters removed? The problem is either a bad adapter preventing proper bus operation or an adapter conflicting with the video card. Reinstall the adapters one at a time, powering up after each one, troubleshooting the problem by elimination.
16. If the motherboard is a new upgrade, try the video adapter in another system before trashing it, since it could be a simple incompatibility.

===================================

Hard Drive Failure Diagnostics / Trouble Shooting

1. If all installed ATA drives are not displayed on the start-up screen - enter CMOS Setup to view and setup the information.
2. Does the hard drive spin up? If not perform power supply diagnostics. Power off, just disconnect the disk drives, put the drive back in and continue with the diagnostics. With PATA drives can push hard on the power connector but do not damage the circuit board.
3. The interface speed for SATA drives is 150 MB/s(SATA 1) or 300 MB/s(SATA 2). If the SATA 2 drive isn't recognized by the BIOS or won't boot reliably, check for the onboard compatibility jumper that will force it to work properly with the older 150 MB/s controller.
4. SATA drives are more reliable then IDE technology. If the drive powers up but isn't recognized by the BIOS, it's possible that the data cable is bad or not properly seated on the drive and the motherboard. If the data cable is known to be good, try attaching it to a different SATA port.
5. If two IDE drives share a single cable, jumpers on the drives to set one to "Master" and the other to "Slave". The boot hard drive should always be the Master on the primary IDE. CD, DVD, or any other IDE drive should be set to Slave.
6. Most new PATA drives support Cable Select (CS) which means the pin 28 connection in the cable will determine Master and Slave. The 80 wire ribbon cables have color coded connectors: Motherboard IDE Connector - Blue, Slave - Grey (middle), Master - Black. Cable select is supported by custom 40 wire ribbon cable and older drives; the jumpers on both drives should be set to cs. Connectors must be seated all the way into the IDE port on both the drives and the motherboard or adapter card if you're are using a RAID adapter.
7. Make sure the power cable is seated in the drive's power socket, try a new ribbon cable.
8. On IDE drives, pin 1 is usually located next to the power cord. The pin 1 on motherboard is normally marked with an arrow, a dot, a white square. If the motherboard won't register any drive you attach, even on new cables, and if those drives are spinning up, it indicates that either the IDE controller is bad or all the drives you've tried are bad. Try on the secondary IDE and the next stop is installing an add-in IDE adapter or replacing the motherboard.
9. The troubleshooting procedures for ATA drives CDs, DVDs, tapes that aren't recognized by the BIOS are identical; try to the CD or DVD Failure diagnostics.
10. If drive cycle up and down, try swapping the power and isolating the drive on ribbon cable, try disconnecting the data cable to ensure that the drive isn't receiving some flaky power down signal from a bad ATA interface or crazy power management scheme. If it still cycles up and down, test the drive in another system or a USB shell before labeling it dead.
11. If you have an old drive that spins up but won't seek (you never hear the head move in and out), it's probably a mechanical failure. Tap lightly with a screwdriver on the cover of the drive, away from the circular section where the disks are spinning. This might encourage a stuck head to get moving. Freezing the drive for a few hours in the freezer (use a sealed bag) may get you temporary access to a drive with failing electronics that overheat. Just make sure you have your backup.
12. If drive make little clicking noises and fail to get going-Restart the machine, hopefully it will boot. If not, try in a warmer room, or put the PC in direct sunlight to warm up and then try it again. If get it started, run Scandisk. Reseat all of the cables on the drive and motherboard, since connections can also loosen up over time. Try FDISK and reinstalling the operating system again.
13. Do the BIOS report the transfer mode correctly - UDMA/100, ATA/66- UDMA must be enabled in CMOS, or set on "Auto," for high speed transfers. IDE hard drives after 1995 require the 80 wire ribbon cable for high speed operation. Check CMOS Setup to see if there's a manual override to select the higher speed transfers, though the automatic settings should pick it up. Also try isolating the hard drive as the sole device on the primary controller.
14. Can you install an operating system, or access the drive with any generation of FDISK to create or view partitions? Check the ribbon cable is fully and evenly seated and there aren't any "read only" jumpers set on the drive (on SCSI's). Try a new ribbon cable. Try FDISK/MBR (rewrite Master Boot Record).

=================================

Optical Disc - CD/ DVD Problems

The most basic and disastrous problem with a CD or DVD drive is a stuck tray. Use the short screws shipped with the drive and not longer screws which can jam the mechanism. Check the power supply lead seating in the drive socket. Shut down, restart, check whether the BIOS register the drive, access CMOS Setup to check. If the BIOS don’t register the drive, it may have dropped dead, do IDE Drive Failure.

If BIOS and OS register-you really have a stuck disc. Look for a pinhole on the front of the CD or DVD drive. Power down the system, unplug the power cord, and gently push a straitened paper clip into the hole, until you feel it depress the release mechanism. This will sometime cause the tray to pop out a fraction of an inch. Once the tray sticks out, grab it with your fingers, you should be able to pull it out, though it can offer quite a bit of resistance, and you may damage whatever disc is inside. If the faceplate seems to be bulging as you pull, the disc is hung up on it, and the best thing to do is remove the drive from the PC and then remove the faceplate, to remove the disk without damaging the disk. It probably isn't repairable without access to parts. At this point, consider sending it out.

Does the drive read other discs? Clean the disc with a soft bit of flannel.

Does the drive show up in the OS, on desktop or in Device Manager in? If not, reinstall the driver.

If you can boot an OS CD in the drive, but the drive has disappeared from Device Manager, try reinstalling the OS.

Try changing the transfer mode the CD is operating in CMOS Setup to a lower speed.

The laser lens in the drive could be incredibly dirty, so find an inexpensive cleaning kit.

Try swapping the power supply or IDE cable.

If the drive is the Slave on IDE1 controller with the hard drive, move it to the IDE2 as Master. If already have another device as the secondary Master, you can try the drive as the secondary Slave or temporarily replace the secondary Master for the sake of seeing if it will work.

Does the drive cause the PC to tremble when it spins up? Is it noisy? Check four mount screws, level. Super high speed drives, over 40X, will vibrates, if disc is un-balanced, or disc weighting problem, physical flaws, a miss-applied label etc. can create an unbalanced disc. Ejecting and reinserting the disc. If the problem occurs with most discs, look into a new drive.

==================

BIOS Beep Codes

AMI BIOS Beep Codes

• 1 Beep – Memory Refresh Failure (check RAM)
• 2 Beeps – Memory Parity Error in first 64KB block (check RAM)
• 3 Beeps – Memory Read/Write Error in first 64KB block (check RAM)
• 4 Beeps – Motherboard timer not functioning (may need to replace the motherboard)
• 5 Beeps – Processor Error (may need to replace the processor)
• 6 Beeps – Gate A20/keyboard controller failure (may need to replace the motherboard)
• 7 Beeps – Processor Exception Interrupt Error (may need to replace the processor)
• 8 Beeps – Display Memory Read/Write Failure (check video card)
• 9 Beeps – ROM checksum Error (replace BIOS chip or motherboard)
• 10 Beeps – CMOS shutdown Read/Write error (possible motherboard replacement)
• 11 Beeps – Bad Cache Memory – test failed (replace cache memory)
Phoenix BIOS beep codes 
They are series of beeps separated by a pause, like beep *pause beep beep *pause beep *pause beep beep
• 1-1-4-1 – Cache Error (level 2) 1-2-2-3 – BIOS ROM Checksum
• 1-3-1-1 – DRAM Refresh Test 1-3-1-3 – Keyboard controller test
• 1-3-4-1 – RAM Failure on address line (check memory)
• 1-3-4-3 – RAM Failure on data bits of low byte of memory bus
• 1-4-1-1 – RAM Failure on data bits of high byte of memory bus
• 2-1-2-3 – ROM copyright notice 2-2-3-1 – Test for unexpected interrupts

Award BIOS beep codes

• one long beep and two short beeps – Video error (check video card)
• two short beeps – Non-Fatal Error (check RAM)
========================

Printers - types, working principles

Inkjet printers operate by propelling variably-sized droplets of liquid or molten material (ink) onto almost any medium. They are the most common type of computer printer for the general consumerdue to their low cost, high quality of output, capability of printing in vivid color, and ease of use. There are three main technologies in use in contemporary inkjet printers: thermal, piezoelectric, and continuous.

Thermal inkjets Most consumer inkjet printers (Lexmark, Hewlett-Packard, and Canon) use print cartridges with a series of tiny electrically heated chambers constructed by photolithography. To produce an image, the printer runs a pulse of current through the heating elements causing a steam explosion in the chamber to form a bubble, which propels a droplet of ink onto the paper (hence Canon's tradename of Bubblejet for its inkjets). The ink's surface tension as well as the condensation and thus contraction of the vapour bubble, pulls a further charge of ink into the chamber through a narrow channel attached to an ink reservoir.

Piezoelectric inkjets - Most commercial and industrial ink jet printers use a piezoelectric material in an ink-filled chamber behind each nozzle instead of a heating element. When a voltage is applied, the piezoelectric material changes shape or size, which generates a pressure pulse in the fluid forcing a droplet of ink from the nozzle. This is essentially the same mechanism as the thermal inkjet but generates the pressure pulse using a different physical principle. Piezoelectric ink jet allows a wider variety of inks than thermal or continuous ink jet but the print heads are more expensive.

The continuous ink jet method is used commercially for marking and coding of products and packages. In continuous ink jet technology, a high-pressure pump directs liquid ink from a reservoir through a gunbody and a microscopic nozzle, creating a continuous stream of ink droplets via the Plateau-Rayleigh instability. A piezoelectric crystal creates an acoustic wave as it vibrates within the gunbody and causes the stream of liquid to break into droplets at regular intervals – 64,000 to 165,000 drops per second may be achieved. The ink droplets are subjected to an electrostatic field created by a charging electrode as they form, the field varied according to the degree of drop deflection desired. This results in a controlled, variable electrostatic charge on each droplet. Charged droplets are separated by one or more uncharged “guard droplets” to minimize electrostatic repulsion between neighboring droplets.

The charged droplets pass through an electrostatic field and are directed (deflected) by electrostatic deflection plates to print on the receptor material (paper), or allowed to continue on undeflected to a collection gutter for re-use. Only a small fraction of the droplets is used to print, the majority being recycled.

Inkjets have a number of advantages. They are quieter in operation, can print finer, smoother details through higher printhead resolution with photographic-quality printing.

Inkjet printers may have a number of disadvantages:The ink is often very expensive; The lifetime of inkjet prints produced by inkjets using aqueous inks is limited; Because the ink used in most consumer inkjets is water-soluble, care must be taken with inkjet-printed documents to avoid even the smallest drop of water, which can cause severe "blurring" or "running."

A dot matrix printer or impact matrix printer refers to a type of computer printer with a print head that runs back and forth on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper, much like a typewriter. Because the printing involves mechanical pressure, these printers can create carbon copies.

Each dot is produced by a tiny metal rod, also called a "wire" or "pin", which is driven forward by the power of a tiny electromagnet or solenoid, either direct ly or through small levers (pawls). Facing the ribbon and the paper is a small guide plate pierced with holes to serve as guides for the pins. The moving portion of the printer is called the print head, and when running the printer as a generic text device generally prints one line of text at a time. Most dot matrix printers have a single vertical line of dot-making equipment on their print heads; others have a few interleaved rows in order to improve dot density as 7x9 pins.

Advantages : Dot matrix printers, like any impact printer, can print on multi-part stationery or make carbon copies, have one of the lowest printing costs per page. As the ink is running out, the printout gradually fades rather than suddenly stopping partway through a job. They are able to use continuous paper rather than requiring individual sheets, making them useful for data logging. They are good, reliable workhorses ideal for use in situations where printed content is more important than quality. The ink ribbon also does not easily dry out, including both the ribbon stored in the casing as well as the portion that is stretched in front of the print head

Disadvantages: Impact printers are usually noisy, print low resolution graphics, with limited color performance, limited quality and comparatively low speed. They are prone to bent pins (and therefore a destroyed printhead) caused by printing a character half-on and half-off the label. (http://mimech.com/printers/)

A laser printer is a common type of computer printer that rapidly produces high quality text and graphics on plain paper. As with digital photocopiers and MFPs, laser printers employ a xerographic printing process but differ from analog photocopiers in that the image is produced by the direct scanning of a laser beam across the printer's photoreceptor. A laser beam projects an image of the page to be printed onto an electrically charged rotating drum. The image is formed of tiny dots. A type of ink is then sprayed onto the drum. Ink only adheres to areas that were illuminated by the beam. The drum then prints the image onto paper by direct contact.

Laser printers have many significant advantages over other types of printers. Unlike impact printers, laser printer speed can vary widely, and depends on many factors, including the graphic intensity of the job being processed. The fastest models can print over 200 monochrome pages per minute (12,000 pages per hour). The fastest color laser printers can print over 100 pages per.

The cost of this technology depends on a combination of factors, including the cost of paper, toner, and infrequent drum replacement, as well as the replacement of other consumables such as the fuser assembly and transfer assembly. Often printers with soft plastic drums can have a very high cost of ownership that does not become apparent until the drum requires replacement.

Instead the image data is built up and stored in a large bank of memory capable of representing every dot on the page. The requirement to store all dots in memory before printing has traditionally limited laser printers to small fixed paper sizes such as letter or A4. Most laser printers are unable to print continuous banners spanning a sheet of paper two meters long, because there is not enough memory available in the printer to store such a large image before printing begins. Its Working: -

Raster image processing : Generating the raster image data Each horizontal strip of dots across the page is known as a raster line or scan line. Creating the image to be printed is done by a Raster Image Processor (RIP), typically built into the laser printer. The source material may be encoded in any number of special page description languages such as Adobe PostScript (PS) or HP Printer Command Language (PCL), as well as unformatted text-only data. The RIP uses the page description language to generate a bitmap of the final page in the raster memory. Once the entire page has been rendered in raster memory, the printer is ready to begin the process of sending the rasterized stream of dots to the paper in a continuous stream.

Charging : Appyling a negative charge to the photosensitive drum. A corona wire (in older printers) or a primary charge roller projects an electrostatic charge onto the photoreceptor (otherwise named the photoconductor unit), a revolving photosensitive drum or belt, which is capable of holding an electrostatic charge on its surface while it is in the dark.

Numerous patents describe the photosensitive drum coating as a silicon sandwich with a photocharging layer, a charge leakage barrier layer, as well as a surface layer. One version uses amorphous silicon containing hydrogen as the light receiving layer, Boron nitride as a charge leakage barrier layer, as well as a surface layer of doped silicon, notably silicon with oxygen or nitrogen which at sufficient concentration resembles machining silicon nitride; the effect is that of a light chargeable diode with minimal leakage, that resists scuffing

Exposing: How the bitmap is written to the photosensitive drum. The laser is aimed at a rotating polygonal mirror, which directs the laser beam through a system of lenses and mirrors onto the photoreceptor. The beam sweeps across the photoreceptor at an angle to make the sweep straight across the page; the cylinder continues to rotate during the sweep and the angle of sweep compensates for this motion. The stream of rasterized data held in memory turns the laser on and off to form the dots on the cylinder. (Some printers switch an array of light emitting diodes spanning the width of the page, but these devices are not "Laser Printers".) Lasers are used because they generate a narrow beam over great distances. The laser beam neutralizes (or reverses) the charge on the white parts of the image, leaving a static electric negative image on the photoreceptor surface to lift the toner particles.

Developing: The surface with the latent image is exposed to toner, fine particles of dry plastic powder mixed with carbon black or coloring agents. The charged toner particles are given a negative charge, and are electrostatically attracted to the photoreceptor where the laser wrote the latent image. Because like charges repel, the negatively charged toner will not touch the drum where light has not removed the negative charge.

The overall darkness of the printed image is controlled by the high voltage charge applied to the supply toner. Once the charged toner has jumped the gap to the surface of the drum, the negative charge on the toner itself repels the supply toner and prevents more toner from jumping to the drum. If the voltage is low, only a thin coat of toner is needed to stop more toner from transferring. If the voltage is high, then a thin coating on the drum is too weak to stop more toner from transferring to the drum. More supply toner will continue to jump to the drum until the charges on the drum are again high enough to repel the supply toner. At the darkest settings the supply toner voltage is high enough that it will also start coating the drum where the initial unwritten drum charge is still present, and will give the entire page a dark shadow.

Transferring:The photoreceptor is pressed or rolled over paper, transferring the image. Higher-end machines use a positively charged transfer roller on the back side of the paper to pull the toner from the photoreceptor to the paper.

Fusing:Melting toner into the paper using heat and pressure. The paper passes through rollers in the fuser assembly where heat and pressure (up to 200 Celsius) bond the plastic powder to the paper.

One roller is usually a hollow tube (heat roller) and the other is a rubber backing roller (pressure roller). A radiant heat lamp is suspended in the center of the hollow tube, and its infrared energy uniformly heats the roller from the inside. For proper bonding of the toner, the fuser roller must be uniformly hot.

The fuser accounts for up to 90% of a printer's power usage. The heat from the fuser assembly can damage other parts of the printer, so it is often ventilated by fans to move the heat away from the interior. Some printers use a very thin flexible metal fuser roller, so there is less mass to be heated and the fuser can more quickly reach operating temperature. If paper moves through the fuser more slowly, there is more roller contact time for the toner to melt, and the fuser can operate at a lower temperature. Smaller, inexpensive laser printers typically print slowly, due to this energy-saving design, compared to large high speed printers where paper moves more rapidly through a high-temperature fuser with a very short contact time.