CompTIA A+ 220-1101

Class A private address range

10.0.0.0 to 10.255.255.255

Post Office Protocol (POP)

110 TCP Retrieve email messages from a server mailbox

NetBIOS over TCP/IP

137-139 UDP/TCP Support networking features of legacy Windows versions

Internet Mail Access Protocol (IMAP)

143 TCP Read and manage mail messages on a server mailbox

Simple Network Management Protocol (SNMP)

161 UDP Query status information from network devices

SNMP trap operation

162 UDP Report status information to a management server

Class B private address range

172.16.0.0 to 172.31.255.255

Class C private address range

192.168.0.0 to 192.168.255.255

File Transfer Protocol (FTP)—Data connection

20 TCP Make files available for download across a network (data connection port)

File Transfer Protocol (FTP)—Control connection

21 TCP Make files available for download across a network (control connection port)

Secure Shell (SSH)

22 TCP Make a secure connection to the command-line interface of a server

Telnet

23 TCP Make an unsecure connection to the command-line interface of a server

Simple Mail Transfer Protocol (SMTP)

25 TCP Transfer email messages across a network

Remote Desktop Protocol (RDP)

3389 TCP Make a secure connection to the graphical desktop of a computer

Lightweight Directory Access Protocol (LDAP)

389 TCP Query information about network users and resources

HTTP Secure (HTTPS)

443 TCP Provision secure websites and services

Server Message Block (SMB)

445 TCP Implement Windows-compatible file and printer sharing services on a local network (also sometimes referred to as Common Internet File System [CIFS])

Domain Name System (DNS)

53 TCP/UDP Facilitate identification of hosts by name alongside IP addressing

Dynamic Host Configuration Protocol (DHCP) Server

67 UDP Provision an IP address configuration to clients

DHCP Client

68 UDP Request a dynamic IP address configuration from a server

HyperText Transfer Protocol (HTTP)

80 TCP Provision unsecure websites and web services

Thermal Inkjet

A pulse of electrical current is applied to heating chambers around the nozzles. The heat creates a bubble of steam in the chamber. The steam forces ink out through the nozzle and onto the paper.

Automatic Private IP Addressing (APIPA)

Allows a networked device to self-assign an IP address from the 169.254.0.0/16 network. Note that this address is only usable on the device's local subnet (meaning that the IP address is not routable).

802.3af

Allows powered devices to draw up to about 13 W. Power is supplied as 350mA@48V and limited to 15.4 W, but the voltage drop over the maximum 100 feet of cable results in usable power of around 13 W.

802.3at (PoE+)

Allows powered devices to draw up to about 25 W, with a maximum current of 600 mA.

Twisted Nematic (TN)

Crystals twist or untwist in response to the voltage level. This is the earliest type of TFT technology and might still be found in budget displays. This type of display supports faster response times than other TFT technologies. Fast response time helps to reduce ghosting and motion trail artifacts when the input source uses a high frame rate.

6. Document the findings, actions, and outcomes

Document the findings, actions, and outcomes

Fusing Stage

From the transfer assembly, the paper passes into the fuser assembly. The fuser unit squeezes the paper between a hot roller and a pressure roller so that the toner is melted onto the surface of the paper. The hot roller is a metal tube containing a heat lamp; the pressure roller is typically silicon rubber. The heat roller has a Teflon coating to prevent toner from sticking to it.

1. Identify the problem

Gather information from the user, identify user changes, and, if applicable, perform backups before making changes. Inquire regarding environmental or infrastructure changes.

Color missing

If a color is completely missing, try replacing the cartridge. If this does not solve the issue, clean the contacts between the printer and cartridge.

Faded or faint prints

If a simple cause such as the user choosing an option for low density (draft output) can be discounted, this is most likely to indicate that the toner cartridge needs replacing.

2. Establish a theory of probable cause (question the obvious)

If necessary, conduct external or internal research based on symptoms.

Incorrect chroma display

If prints come out in the wrong color (for example, if the whole print has a magenta tint), ensure that the toner cartridges have been installed in the correct location (for instance, that a magenta cartridge hasn't been installed in the cyan slot). Also ensure that there is sufficient toner in each cartridge. If there is a cast or shadow-like effect, the transfer belt or one or all of the cartridges or rollers are probably misaligned. Try reseating them, and then run the printer calibration utility and print a test page to verify the problem is solved.

Epson Design Inkjet

In the Epson design, the nozzle contains a piezoelectric element, which changes shape when a voltage is applied. This acts like a small pump, pushing ink through the nozzle and drawing ink from the reservoir.

Charging Stage

In the charging stage, the imaging drum is conditioned by the primary charge roller (PCR). The PCR is a metal roller with a rubber coating powered by a high voltage power supply assembly. The PCR applies a uniform -600 V electrical charge across the drum's surface.

3 long beeps

Keyboard issue (check that a key is not depressed).

Processing Stage

Laser printers produce output as a series of dots. The OS driver encodes the page in a page description language and sends it to the print device. In the processing stage, the printer's formatter board processes the data to create a bitmap (or raster) of the page and stores it in the printer's RAM.

Developing Stage

Laser toner is composed of a fine compound of dyestuff and either wax or plastic particles. The toner is fed evenly onto a magnetized developer roller from a hopper. The developer roller is located very close to the photosensitive drum. The toner carries the same negative charge polarity as the drum, which means that, under normal circumstances, there would be no interaction between the two parts. However, once areas of charge have been selectively removed from the photosensitive drum by the laser, the toner is attracted to them and sticks to those parts of its surface. The drum, now coated with toner in the image of the document, rotates until it reaches the paper.

Speckling on output

Loose toner may be getting onto the paper. Clean the inside of the printer using an approved toner vacuum.

Vertical or horizontal lines

Marks that appear in the same place (referred to as repetitive defects) are often due to dirty feed rollers (note that there are rollers in the toner cartridge and fuser unit too) or a damaged or dirty photosensitive drum.

1 long, 1 short beep

Motherboard problem.

1 short beep

Normal POST- system is OK. Most modern PCs are configured to boot silently, however.

3. Test the theory to determine the cause

Once the theory is confirmed, determine the next steps to resolve the problem. If the theory is not confirmed, re-establish a new theory or escalate.

Toner not fused to paper

Output that smudges easily indicates that the fuser needs replacing.

2 short beeps

POST error- error code shown on screen.

Repeating short beeps

Power supply fault or motherboard problem.

No beep

Power supply, motherboard problem, or faulty onboard speaker.

Continuous beep

Problem with system memory modules or memory controller.

4. Establish a plan of action to resolve the problem and implement the solution

Refer to the vendor's instructions for guidance.

802.3bt (PoE++ or 4PPoE)

Supplies up to about 51 W (Type 3) or 73 W (Type 4) usable power.

IEEE 802.11a

The IEEE 802.11a standard uses the 5 GHz frequency band only. The data encoding method allows a maximum data rate of 54 Mbps. The 5 GHz band is subdivided into 23 non-overlapping channels, each of which is 20 MHz wide.

IEEE 802.11b

The IEEE 802.11b standard uses the 2.4 GHz frequency band and was released in parallel with 802.11a. The signal encoding methods used by 802.11b are inferior to 802.11a and support a nominal data rate of just 11 Mbps.

IEEE 802.11g

The IEEE 802.11g standard offered a relatively straightforward upgrade path from 802.11b; uses the same encoding mechanism and 54 Mbps rate as 802.11a but in the 2.4 GHz band used by 802.11b and with the same channel layout. This made it straightforward for vendors to design 802.11g devices that could offer backwards support for legacy 802.11b clients.

IEEE 802.11n

The IEEE 802.11n standard introduced several improvements to increase bandwidth. It can work over both 2.4 GHz and 5 GHz. The 802.11n standard allows two adjacent 20 MHz channels to be combined into a single 40 MHz channel, referred to as "channel bonding." The other innovation introduced with 802.11n increases reliability and bandwidth by multiplexing signal streams from 2-3 separate antennas. This technology is referred to as " multiple input multiple output" (MIMO). The nominal data rate for 802.11n is 72 Mbps per stream or 150 Mbps per stream for a 40 MHz bonded channel, and 802.11n access points are marketed using Nxxx designations, where xxx is the nominal bandwidth. As an example, an N600 2x2 access point can allocate a bonded channel two streams for a data rate of 300 Mbps, and if it does this simultaneously on both its 2.4 GHz and 5 GHz radios, the bandwidth of the access point could be described as 600 Mbps. In recent years, Wi-Fi standards have been renamed with simpler digit numbers; 802.11n is now officially designated as Wi-Fi 4.

Exposing Stage

The surface coating of the photosensitive imaging drum loses its charge when exposed to light. In the exposing stage, as the laser receives the image information, it fires a short pulse of light for each dot in the raster to neutralize the charge that was applied by the PCR. The pulsing light beam is reflected by a polygonal mirror through a system of lenses onto the rotating photosensitive drum. The drum ends up with a series of raster lines with charge/no-charge dots that represent an electrostatic latent image of the image to be printed.

Transferring Stage

The transferring stage moves the toner from the drum onto the print media. The paper transport mechanism includes components such as gears, pads, and rollers that move the paper through the printer. Pickup components lift a single sheet of paper from the selected input tray and feed it into the printer. To do this, a pickup roller turns once against the paper stack, pushing the paper into a feed and separation roller assembly. This assembly is designed to allow only one sheet to pass through. When the paper reaches the registration roller, a signal tells the printer to start the image development process. When the drum is ready, the paper is fed between the imaging drum and the high voltage transfer roller. The transfer roller applies a positive charge to the underside of the paper. This causes the toner on the drum to be attracted to the paper. As the paper leaves the transfer assembly, a static eliminator strip (or detac corona) removes any remaining charge from the paper. This is done to avoid the paper sticking to the drum or curling as it enters the fuser unit.

White stripes

This indicates either that the toner is poorly distributed (give the cartridge a gentle shake) or that the transfer roller is dirty or damaged.

Black stripes or whole page black

This indicates that the primary charge roller is dirty or damaged or that the high voltage power supply to the developer unit is malfunctioning. Try printing with a known good toner cartridge.

Double/echo images

This is a sign that the photosensitive drum has not been cleaned properly. The drum is smaller than the size of a sheet of paper, so if the latent image is not completely cleared, it will repeat as a light "ghost" or dark "shadow" image farther down the page. Images may also appear from previous prints. Try printing a series of different images, and see if the problem resolves itself. If not, replace the drum/toner cartridge.

Blank pages

This is usually an application or driver problem, but it could indicate that a toner cartridge has been installed without removing its packing seals. Alternatively, if these simple causes can be discounted, this could also be a sign that the transfer roller is damaged (the image transfer stage fails).

Cleaning Stage

To complete the printing cycle, the photosensitive drum is cleaned to remove any remaining toner particles using a cleaning blade, roller, or brush resting on the surface of the drum. Any residual electrical charge is removed, using either a discharge (or erase lamp) or the PCR.

In-Plane Switching (IPS)

Uses crystals that rotate rather than twist. The main benefit is to deliver better color reproduction at a wider range of viewing angles. Most IPS panels support 178/178 degree horizontal and vertical viewing angles. The main drawback of early and cheaper IPS screens is slightly worse response times. A high-quality IPS display will usually be the best TFT option for both gaming and graphics/design work, however, as it will be capable of similar response times to TN while retaining better color reproduction and viewing angles.

Vertical Alignment (VA)

Uses crystals that tilt rather than twist or rotate. This technology supports a wide color gamut and the best contrast-ratio performance. Contrast ratio is the difference in shade between a pixel set to black and one set to white. For example, where a high-end IPS panel might support a 1200:1 contrast ratio, a VA panel would be 2000:1 or 3000:1. However, viewing angles are generally not quite as good as IPS, and response times are worse than TN, making a VA panel more prone to motion blur and ghosting.

5. Verify full-system functionality and, if applicable, implement preventive measures

Verify full-system functionality and, if applicable, implement preventive measures

1 long, 2 or 3 short beeps

Video adapter error.

Wi-Fi 5 (802.11ac)

Wi-Fi 5 is designed to work only in the 5 GHz band. A dual band access point can use its 2.4 GHz radio to support clients on legacy standards (802.11g/n). A tri band access point has one 2.4 GHz radio and two 5 GHz radios. Wi-Fi 5 allows up eight streams, though in practice, most Wi-Fi 5 access points only support 4x4 streams. A single stream over an 80 MHz channel has a nominal rate of 433 Mbps. Wi-Fi 5 also allows wider 80 and 160 MHz bonded channels.

Wi-Fi 6 (802.11ax)

Wi-Fi 6 improves the per-stream data rate over an 80 MHz channel to 600 Mbps. As with Wi-Fi 5, products are branded using the combined throughput of all radios. For example, AX6000 claims nominal rates of 1,148 Mbps on the 2.4 GHz radio and 4,804 Mbps over 5 GHz. Wi-Fi 6 works in both the 2.4 GHz and 5 GHz bands. The Wi-Fi 6e standard adds support for a new 6 GHz frequency band. 6 GHz has less range, but more frequency space, making it easier to use 80 and 160 MHz channels. Where Wi-Fi 5 supports up to four simultaneous clients over 5 GHz only, Wi-Fi 6 can support up to eight clients, giving it better performance in congested areas. Wi-Fi 6 also adds support for uplink MU-MIMO, which allows MU-MIMO-capable clients to send data to the access point simultaneously. Wi-Fi 6 introduces another technology to improve simultaneous connectivity called " orthogonal frequency division multiple access" (OFDMA). OFDMA can work alongside MU-MIMO to improve client density—sustaining high data rates when more stations are connected to the same access point.