IEEE 802.11 WLAN Standards

IEEE 802.11 is a set of standards for wireless network to provide wireless devices with a communication in the 2.4, 3.6 and 5 GHz frequency bands. They are originally developed and maintained by the IEEE (Institute of Electrical and Electronics Engineers) LAN/MAN Standards Committee (LMSC).

The first standard was created by IEEE in 1997 and had been named as 802.11. It uses unregulated radio signaling frequency (2.4 GHz) but only supported up to 2 Mbps maximum network bandwidth. Specific physical layers that enabled three faster radio layers had been defined by subsequent amendments of IEEE 802.11:
802.11b
802.11b was created based on the specification of original 802.11 in July 1999, and it support network bandwidth up to 11 Mbps.
802.11b uses unregulated radio signaling frequency (2.4 GHz) as same as the original 802.11 standard. It provides 3 radio channels. By using this frequency, the manufacturing costs could be lower down. Because of unregulated signal, 802.11b could incur interference from other appliances using the same 2.4 GHz range, such as microwave ovens, cordless phones. However, the interferences can be avoided by installing 802.11b a reasonable distance from other appliances.

• Pros of 802.11b – cost is cheapest; signal range is very good and not easily to be obstructed.
• Cons of 802.11b – maximum speed is still slower; home appliances may interfere on the unregulated frequency band.

802.11a
A second extension to the original 802.11 standard was created and called 802.11a. Due to its higher cost, 802.11a is usually found on business networks whereas 802.11b better serves the home market.
802.11a supports up to 54 Mbps network bandwidth and provides 8 radio channels in the 5 GHz frequency band. Because of this higher frequency, the range of 802.11a networks is also shortened. In addition, the higher frequency also makes the signal of 802.11a to have more difficulty in penetrating walls and other obstacles.

• Pros of 802.11a – faster maximum speed; regulated frequencies can get rid of signal interference from other home appliances.
• Cons of 802.11a – expensive in cost; shorter range signal and more easily to be obstructed.

802.11g
802.11g was created to combine the best of both 802.11a and 802.11b and supports network bandwidth up to 54 Mbps. It uses the 2.4 GHz frequency for wider range. 802.11g is backwards compatible with 802.11b, which means the access point of 802.11g will just work fine with all the wireless network adapters of 802.11b, and vice versa.

• Pros of 802.11g – fast maximum speed; signal range is very good and not easily to be obstructed.
• Cons of 802.11g – cost is higher than 802.11b; other appliances may interfere on the unregulated.

802.11n
802.11n is the newest IEEE standard in the 802.11 family. It improves on 802.11g in the amount of bandwidth by using multiple wireless signals and antennas instead of one. This is a technology called MIMO (multiple-input multiple-output). It will also operate on the 2.4 GHz band. Presently the development of this standard is still in progress. But when this standard is finalized, 802.11n connections will be able to support data rates up to 100 Mbps. 802.11n also offers better range over earlier 802.11 standards due to its increased signal intensity.

• Pros of 802.11g –best signal range and fastest in maximum speed; more ability to resist signal interference from other sources.
• Cons of 802.11g –cost is higher than 802.11g; the use of multiple signals may massively be interfered by nearby 802.11b or 802.11g based networks.

Multiple RDP (Remote Desktop) sessions on Windows 8

Windows 8 Pro (as well as all previous Windows client OS version) allows only one concurrent user session. This means you can't connect via Remote Desktop if local user is already logged on. Normally it's not a problem on client machines, but it some situations you may want ability to login concurrently. A good example is a Media Centre PC when somebody watches a movie and you want to make changes to the machine without interrupting the movie.
To have multiple RDP sessions working you normally need server version of termsrv.dll file and also make certain registry changes.
Peter Kleissner has written and published a little utility which does all the job automatically. In case original source becomes unavailable, you can download version 1.8 from here. (Click Here To download) . If you are not keen on running unknown executables on your machine, source code is also available. You are welcome to inspect and compile it yourself.

Thumbnail Previews Not Showing in Windows 8 Explorer

And if I viewed a directory full of videos in Windows 8, I would get the same thing, just with the default video icon:


This was getting really annoying and I realized it was doing this since the time I installed Windows 8 on the PC. I’m not sure why it’s defaulted to this view instead of thumbnail previews like it is in Windows 7, but if you want the thumbnails back in Windows Explorer, here’s how to do it.
First, open Windows Explorer and then click on Options and Change folder and search options.

Next, click on the View tab and uncheck the box that says Always show icons, never thumbnails.

Once you get rid of that checked option, you should now get thumbnails for all your pictures, videos and even documents.

There is one other place that you can adjust the setting for showing icons or thumbnails in Windows Explorer. First right-click on Computer on the desktop and choose Properties. Then click on Advanced System Settings on the left side.

This will open up the System Properties dialog. Here you need to click on the Advanced tab and then click on Settings.

Finally, make sure Show thumbnails instead of icons is checked.

With these two settings, you should now be seeing thumbnail previews for pictures, videos, documents, and other file types in Explorer on Windows 8. If you’re still seeing just icons, post a comment here and I’ll try to help. Enjoy!

 

Windows Explorer Doesn’t Show Thumbnail Previews in Windows Vista and 7 and server version

Actually its a very common problem in Windows. Sometimes Windows Explorer doesn't show thumbnail previews for images and other files as shown in following screenshot:

It might be due to a bug or the user accidentally turned off thumbnails using Folder Options or System Properties.
Anyway if you are also facing this problem, you can use following easy fix to show thumbnails again in Windows Explorer:
1. Open Windows Explorer, click on Organize button present in command bar and select "Folder and search options".
2. Now go to View tab and make sure "Always show icons, never thumbnails" option is not enabled i.e. its disabled.

If the option is enabled, uncheck the checkbox and click on Apply button.
It should fix the problem. If you can't access Folder Options, you can use following alternative method:
1. Type sysdm.cpl in RUN or Start Menu search box and press Enter. It'll open System Properties.
2. Go to "Advanced" tab and click on "Settings" button in "Performance" section.
3. Now make sure "Show thumbnails instead of icons" option is enabled.

If its not enabled, enable the option and click on Apply button.
That's it. Now you should get thumbnail previews in Windows Explorer without any problem as shown in following screenshot:

Laptop Battery Tips

Laptop Battery Tips

Optimizing laptop battery usage is very important to increase the battery life and performance.

Following are the Top tips to optimize the laptop battery :

• Buy smart: Look for notebooks with low power consuming processors like the Intel’s “CULV” “Consumer Ultra-Low Voltage” processors or AMD processors with “cool & Quiet” feature.
• Dim screen brightness: Choose an environment with adequate lighting—less brightness means you’ll drain less power from your battery.Use the Function key (Fn) available in most of the laptops to dim the brightness.
• Run your applications wisely: To get the most from your laptop, even when multitasking on the go, run resource intensive applications just when actively using them. Then make sure to close the applications you aren’t using.Running Video on the laptop will consume the battery very fast.Avoid to run video almost all time.
• Close unused applications: Programs will still use power while sitting idle.Also some unrequired background processes can  be closed using the task manager.Stop such processes from starting at boot.
• Have the right RAM for your needs: With appropriate RAM, instructions run off memory instead of disk. Less power is needed to refresh the RAM than to spin the hard drive.So increasing the RAM in in the laptop with high resource usage works will highly improve the battery life.
• Clean your battery: Rub the battery’s metal contacts with rubbing alcohol every two months. Allow to dry before re-inserting.
• Remove extra accessories: Unplug items like PC cards, USB and FireWire devices that are not being used.
• Use built-in power management devices: Enable this feature and set your system to “Battery Optimized” mode or “Max Battery” mode. Put your computer to sleep earlier and turn off the screen backlight sooner.Start > Control Panel > Power Options (in Classic View).
• Disable Wi-Fi and Bluetooth if not being used: Wireless LAN and Bluetooth access uses power even when it is not in use. Transmitting and receiving data drains the battery.
• Defragment your hard drive regularly: The built-in defrag utility included with Windows  will take your file fragments and put them closer together on your hard drive, which will decrease hard drive access times and save battery life.
• Use Direct Power as much as possible : Keep your laptop connected to the direct power supply using the laptop power adapter as much as possible.
• Connect laptop to UPS supply : If possible then connect your laptop to UPS supply.This will save your laptop from power fluctuations and if there are frequent power cuts then your laptop battery life-cycle will not be wasted.
• Use battery only when on move : Try to power laptop through battery only when you are on move or if there is no power supply.

SMPS Problems and Solutions

SMPS Problems and Solutions

SMPS

SMPS Internal

What is SMPS ?

SMPS - Switched Mode Power Supply. An SMPS is  a Device to efficiently provide a regulated output voltage, from  different level of  the input voltage.S MPS transfers power from a source like the electrical power grid to a load  (Eg: Computer).

SMPS Connection Diagram

The SMPS in a conventional desktop system is designed to convert the 220V AC, 50HZ into +5V, -5V, +12V and +3.3 V DC

Diagram -SMPS

Tips For Power Supply Service

1. Be sure that the line- voltage  switch(120/220 Vac) is set correctly for your region.

2. Do Not Use a Splitter

3. Be sure that each output is within tolerence(Volatge tolerences are usually +or-5%

4. Verify that the power-supply connectors are attached to the motherboard drivers

5. Check the AC Input voltage with the help of a Multimeter

Troubleshooting SMPS

Problem 1: The Power doesn't come on.

Solutions

1. Check the Power from the wall socket

2. Check the Voltage Setting On the CPU

3. Check the  Power switch  of the Cabinet and  Front Panel of MotherBoard

4. Check the Power Supply Connections to the Motherboard

5. Check the SMPS without connecting it to the motherboard, you could see the two wire green and black which you have to short them (using any piece of wire/paper clip) in the 24 pin motherboard connector of the SMPS.

  Problem 2: The PC Powers on after the second or third try

Solutions 

1. Check the  Power switch  of the Cabinet

2. Replace  SMPS  (Get a Better Quality SMPS)

 Problem 3: The PC Powers on but nothing happens after that (no beep)

Solutions 

 1. Remove the last hardware component installed and check again

2. Replace  SMPS  (Get a Better Quality SMPS)

3. Check the power cables to the  Devices(Harddisk, DVD Drive etc)

 Problem 4: The PC Powers on beeps and stops. NO Power On Self Test (POST)messages

Solutions 

1. Check with another SMPS

2. This may be a Motherboard Problem.

 Problem 5: The PC Powers on runs POST but there is no display

Solutions 

1. Check the Monitor and the VGA Cable Connectons

2. Check with another SMPS

3. This may be a Display Card Problem

 Problem 6: There is a squealing/whistling/whining noise from SMPS when the PC starts

Solutions 

1. Check the SMPS Fan

2. Component problem with SMPS. Replace it 

Problem7: The PC freezes or reboots suddenly

Solutions 

1. Check the SMPS Fan (May be overheating Problem)

2. Replace the SMPS

Computer Hardware Troubleshooting Guide for beginners.

Here are some techniques to solve common computer hardware problems. I used to do these techniques over 15 years. In my experience, I would like to say "don’t panic to decide anything at a glance of view". Take your time and decide the right.

Most common problems in computer hardware are, loose connections. So first try to tie up all peripherals, connectors properly before do anything

First I would like to say, this Diagnostics tips are not for the servers, this is just for the desktop Computers. OF course, some remedies are applicable for the Notebooks also.

The most reliable way is, try to isolate the problem by using compatible peripherals from other computers. (If you are a trainee hardware technician, it’s better to have extra standard PC peripherals with you for testing purpose). In this way you can isolate the defective part(s) easily rather than guessing. But of course, keeps in your mind that, if you isolate the defective part(s) don’t forget to fully test the PC with new part(s). It because’ sometimes there may be another problem in addition to this defective part(s). And don’t forget to Re-test the faulty part. And always do test one at a time.

Here are some precautions before the Diagnose or troubleshooting.

1. Never replace a Computer peripheral, when main power code is connected to the power supply.
2. Never touch a Computer peripheral with wet or sweat hands. Keep your hands clean when you handle them.
3. If you can always use an anti statistic computer repair kit.
4. Always use the proper tools.
5. Never use teeth to clean or cut wires or any other electronic, electric parts.
6. Always have a good power codes/ extension board and earthling system with your house/Office power system.

So here we go…

No Power

1. If computer doesn’t power up at all, Reset the BIOS first and try.
2. If still not power up, disconnect all the peripherals and wire harnesses except, Processor, and power supply, then try to switch on from mother board’s front panel connector.
3. If still not power up change the power supply and try.
4. If still not power up remove the mother board with processor from Casing and lay it on antistatic surface and plug a power supply and try.
5. If still it’s happening same problem, replace the processor and try.
6. If it’s not work it because faulty mother board.

Power Comes but no Display

1. Remove the RAM card from the mother board and clean it with rubber eraser and re-plug it and try.
2. Replace a RAM card and try.
3. If it’s having both separate and On board VGA, pull the separate VGA card and try with On-board’s VGA out.
4. If it’s having a separate VGA card, Remove the VGA card from the mother board and clean it with rubber eraser and re-plug and try.
5. If it has only separate VGA card replace the VGA card and try.
6. Reset the BIOS and try.
7. If still not Display, disconnect all the peripherals and wire harnesses except, Processor, RAM card (VGA card, if available) and power supply, and then try to switch on from mother board’s front panel connector. (If computer has separate VGA card and on-board VGA as well, proceed with onboard VGA until isolate the defective part).
8. If still no display, remove the mother board with processor, RAM card and VGA card from Casing and lay it on antistatic surface and plug a power supply and try.
9. Replace the processor and try.
10. Replace the Power supply and try.
11. Still it’s not display means faulty mother board.

Display comes, OS not loading.

1. Check if any abnormal sound comes from the Hard Disk drive. (If so it’s a faulty HDD).
2. Check whether Cooling FANs are working in order.
3. Re-plug all HDD connectors and try.
4. Replace the HDD interface cable and try.
5. Check whether HDD is detected by Mother board (Drive details on the BIOS) if not use a another HDD port (SATA or IDE) on mother board.
6. Reset the BIOS and try.
7. If you have a spare HDD attach it with the faulty PC and check whether mother board detects it.
8. Try to start with safe mode or Last known good configuration mode, by pressing F8 at the startup, if it’s restating.
9. Check the HDD mode (ACHI or IDE) on Advance chip set settings in the BIOS and set the proper setting.
10. Detach if PC has DVD drives, additional Add-On cards and USB cables and try.
11. Replace the RAM card and try.
12. If it’s a windows PC, Remove the HDD from the faulty PC and attach it with healthy PC as a secondary HDD. If that HDD is having a problem with file system, it will run the scan disk utility automatically. After run the scan disk, shut down the testing PC gently and re attach the faulty PC and try.
13. If you are in a position to reinstall the PC at once without doing any software solution do it right now or do fresh OS installation with another HDD.
14. If it’s a hardware error in most cases now you will face it while installing the OS. In such case you have to replace and try with RAM, HDD, Processor and (Separate VGA if you have).

Computer is restarting or getting off, automatically. (Occasionally).

1. First before replacing anything checks the all Cooling FANs are working properly.
2. Re-plug all the Connecters tiredly and Clean all the contacts of RAM, VGA and Other Add-On cards with rubber eraser.
3. Disconnect the HDD and switch on the PC and let it run. If it runs for considerable time, most probably power supply is OK.
4. Then re-Attach the HDD and Run a scan disk for HDD and check.
5. Run a third party RAM test.
6. Disconnect USB cables or any other Add-On card and test.
7. If it’s having a separate VGA card On-board VGA card, try on On-board VGA card. Otherwise replace the VGA card and Try.
8. Disable any Power saving feature or Screen server on the OS and try.
9. Update the Latest BIOS version for Mother Board.
10. If still happens you have to replace RAM, VGA card, Processor, HDD, HDD interface cables ultimately power supply. Replace one at a time and check.
11. After replacing a peripheral, here is some test run I always do for detect these types of errors. Create a note pad Document and write this syntax ( Dir /s “pres Enter” a.bat) save it on the desktop and exit while re-naming this file as a.bat (.TXT extension should be .BAT) then double click on that icon and it will run. Right click again and again on this icon. Then it will run number of sessions. 50 sessions is enough. In this way you can make the busy on PC and test whether Problem is Solve or not.

How we deal with faulty parts?

If you found faulty VGA card, RAM card and Mother Boards, don’t forget to wash with fresh water and dry it well and try again. (If not they have any warranty).

Same time if you have a facility to resold the circuit boards of defective Computer part’s (Chips and Chip’s soldering spots) (such as Mother boards, RAM cards, VGA cards, Processors, HDDs Circuit boards) from a heat blower, do it and try. And most of the time you may see defective capacitors, in that case if have a little ability to replace the Cap, can do it by yourself (If not they have any warranty).

if you got defective power supplies don’t discard it. Open the power supply box and re-sold the circuit board and try. (If not they have any warranty).