Troubleshooting linear power supply was quite easy as compare to switch mode power supplies (SMPS). AC voltage enters to the primary side of linear transformer and then converted the AC into a lower or higher AC voltage depending on the secondary winding. The output AC voltage is then rectified and filtered by a diode and capacitors to produce a clean DC voltage. If there is a problem in the linear transformer circuit, I can say that it is very easy to locate the fault. This is somehow different in the case of a switch mode power supply. The designs were complicated and some technicians found it quite hard to fully understand how the switch mode power supplies work.

The working principle of switch mode power supply is different from the linear type. First the AC voltage will flow to a full wave rectifier (bridge rectifier) which produces an uneven DC output and then filtered by a large capacitor (usually 220 micro farad and up to 450 volts). The clean DC voltage will then flows to start up resistors and to the input of switch mode power transformer. Once the voltage passed through the high ohms resistor (start up resistors) the voltage would drop to a value where it then flows to the VCC supply pin of Pulse width modulation IC.

Once the PWM IC received the voltage it will output a signal to drive the transistor (or FET) and produces a changing in magnetic field in the transformer primary winding. The changing magnetic field induces voltage in the secondary windings. Each of these AC voltage produced by the secondary windings is then rectified, filtered, and regulated to produce a clean DC voltage. One of the main DC output voltage is the B+ that supply to flyback transformer (for TV and Monitor Circuit)

The output from the B+ voltage supply is then connected, through a “feedback” loop (which consist of optoisolator ic and an error amplifier TL431 IC), back to the PWM IC. When the voltage from the B+ supply rises or drop a bit, the PWM IC will act to correct the output.

If you still do not understand the above explanation, please do not be discourage because you can always buy technical books and schematic diagrams and read it till you get the whole idea of how a SMPS work. You can ask a repair friend or even surf the internet for a better and easy explanation.

Here I would like you to download a free SMPS article by Sencore and I found it to be a great help for you who are still struggle on how SMPS work and how to troubleshoot when it fails. You must ask your self what is the purpose and its function of the components in the SMPS circuit and how to check them if they fail. Find out on your own the function of these components in SMPS circuit:

Bridge rectifier,

Filter capacitor,

Start up resistors

Chopper/Power FET

Pulse Width Modulation (PWM IC)

Current sense resistor

Switch mode power transformer

Optoisolator/optocoupler

Error Amplifier IC (TL431)

Secondary diodes

Secondary filter capacitors

Push yourself further by searching the internet for the datasheet of a PWM IC part number. For example, UC3842 PWM IC is mostly used in SMPS. Do you know what the function of pin 5 of this IC is? Do you know which pin the VCC supply enters? Do you know what the actual voltage that flow to the IC is? Do you know which pin that drives the power FET? Can I get a replacement for this IC? And so on………

Let’s take a soldier as an example. Soldiers not only good in handling rifle but also knows all the details about it. They know how to dismantle and assemble back their rifle fast (imagine in the middle of war the rifle jammed-they can repair it fast). They know how much each bullet cost, how far the shooting distance, how big is the diameter of the bullet, how many cm the length of the bullet and so on. Hope you don’t get bored with the soldier’s story, did you get the ideas?

Any SMPS that comes across my repair bench, I would not immediately repair it, in fact I will take couples of minutes to analyze the circuit design and see it from all angles before I begin to repair. Troubleshooting SMPS is not limited to only one procedure in fact many electronic repairers have their own unique ways and methods to solve SMPS problems. Some prefer to use light bulb to isolate SMPS faults while others like to use resistors. Troubleshooting SMPS is fun and flexible but in some cases could make you get very frustrated too.

Remember, don’t limit yourself to only one or two sources to get you understand and be able to repair SMPS. If you have the budget, get the books that have related to SMPS repair-study and start doing practical about it. Share your problems with other fellow electronic repairers and the most important thing is don’t give up. There’s lot of mountain in the journey of our live and you yourself have to climb and conquer it. All the best!

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www.bug-transmitter.com Many thanks to talkingelectronics. In this video we are showing you how to make a FM transmitter Bug using 2 transistors and with a transmission range of 800 meters !! This FM transmitter Bug is very easy to build. The size of the circuit board is ONLY 21mm x 15mm. I design the circuit board layout using Pain shop pro X2 ,it takes me 2 hours to get the design right ,i want a very small PCB. To make the PCB i will be using the toner transfer method and Ferric Chloride. Parts used Home made PCB ,21mm X 15mm BC547 transistors x 2 1nf ceramic capacitor 10pf ceramic capacitor 33pf ceramic capacitor 22nf axial ceramic capacitor x 2 1 – 5p to 30p air trimmer 470R resistor 10K resistor 47K resistor 68K resistor 1M resistor 10mm Mic 175cm antenna Battery Plug Some solder 19mm heatshrink

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Ultraviolet LED lights are used for anti-counterfeiting purposes. This type of lighting can replace the technology of black lights. This can actually illuminate watermarks on currencies and documents so inspectors can see traces of fraud. Also, this is a good device that can get rid of harmful micro organisms. Most micro organisms known to science are sensitive to UV rays and they immediately die when they absorb this. This can be used to disinfect and sterilize things at home especially those used by babies.

This is expensive if you purchase it from the market. This is why home-made UV LEDs projects were introduced. The following is a do it yourself project one can easily follow at home:

Step 1: Purchase your UV LED bulb from the electronics store first. If the nearest store do not have this in their inventory, you can always scour for good finds online. Also purchase the other materials you are going to need such as ¼ watts of 100 ohm resistor.

Step 2: Buy an inexpensive flashlight, preferably one that uses 1.5 volt batteries-4 batteries. Use this flashlight but you only need to remove a few parts and replace it with the UV ones.

Step 3: Now remove the head of the flashlight and the lid that covers the bulb. Gently remove the bulb. Some flashlights have easy to remove bulbs-you might need only to give it a little pull while some requires you to remove some screws first.

Step 4: Once you have already removed the old bulb, install the new one. Use a clamp to position it to the right place and then use a soldering iron to heat up the bottom part of the bulb.

Step 5: After the bulb has cooled down, solder the 100 ohm resistor this time. Attach it to the positive lead. Locate the positive lead of the flashlight. It is usually the longer end. Get the shorter end and fold it so you can make a right angle. Snip off the excess part of the positive lead. Also snip off the leads of the resistor so they have half an inch of size.

Step 6: Now solder the resistor to the positive end of the lead. Make sure you have inserted the longer lead to the bottom part of the bulb. There should be a hole there so you can insert the lead.

Step 7: Now you can assemble the outer covering and use the UV LED flashlight you have created.

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Hey, this is an introduction for building your very own LED audio meter (known as PFL). You can find these meters on almost every mixer, however the number of lights (= precision) varies among brands. In the next video I will show you how you can built this using general electronic parts. This project is great if you don’t have a nice PFL meter like this one on you mixer. It is also a very cool light effect near your dj-booth. If you want to built this with me watch the upcoming video where i show you how to assemble this unit. You can already buy the following parts at an electronics specialist: 1 Resistor 1 kΩ 1 Condensator 2,2 µF 10 LED’s (any color you want) 1 LM 3915 A piece of blank prototype board Any battery between 2-10 volts Soldering is required! Practice and Enjoy

http://www.youtube.com/watch?v=s1IxV2krKwg&hl=en

Vishay-Beyschlag 4.75K ohm Surface Mount Thin Film Precision Resistor 0603 0.1% 1/10W 25ppm 2312-201 (Continuous strip of 10)

Vishay-Beyschlag 4.75K ohm Surface Mount Thin Film Precision Resistor 0603 0.1% 1/10W 25ppm 2312-201 (Continuous strip of 10) Feature

• Resistance: 4.75K ohms
• Case Type: 0603
• Tolerance: 0.1%
• Wattage: 1/10 watts
• Temperature Coefficient: 25ppm

Vishay-Beyschlag 4.75K ohm Surface Mount Thin Film Precision Resistor 0603 0.1% 1/10W 25ppm 2312-201 (Continuous strip of 10) Overview

Vishay-Beyschlag 4.75K ohm Surface Mount Thin Film Precision Resistor 0603 0.1% 1/10W 25ppm 2312-201 100% TIN RoHS (Continuous strip of 10)

Vishay-Beyschlag 4.75K ohm Surface Mount Thin Film Precision Resistor 0603 0.1% 1/10W 25ppm 2312-201 (Continuous strip of 10) Specifications

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*** Product Information and Prices Stored: Apr 24, 2011 11:12:24