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Our news letter is starting to get alot of subscribers.Come take a look and join for yourself, in just a couple days I will be sending out the July News Letter and it will have some good info.Preher TV sends out an informative News Letter every month , but it only gets sent to subscribers so join today!!Learn more by clicking here or by clicking the photo below.

This is a good reference manual on SMPS that I found online.I love reading every day and find it to be very important for a repair technician to help fully understand all the circuits we work on and improve your trouble shooting skills.When you fully understand how circuits work trouble shooting failures becomes easy.This manual will help you to understand how SMPS works.Please click here or click on the photo below to download and read this reference manual.Have a great day and remember to keep reeding about electronics every day, even if it's reading something you have read before just to keep things fresh in your mind.

Flat-panel liquid LCDs are the display of choice in a wide range of portable products from notebook
computers, tablet PCs, and PDAs to digital cameras and portable instrumentation. Compact coldcathode
fluorescent lamps (CCFLs) provide the necessary light source in these applications, enabling a
readable display in both dim and bright ambient light.
Inverters that supply the power to turn on (strike) and run CCFLs control one of the major power
drains in any battery-powered device. These are technically challenging circuits. First, inverters must
accept a wide range of dc input voltages, typically from 3 to 14 V, and provide ac outputs of 500 to
800 V to run the lamps. Then, to ignite CCFL lamps, these circuits must provide momentary strike
voltages that typically are twice that of their run voltages. Many applications also require efficient
dimming capabilities to allow lamp output to match ambient light conditions and thus prolong both
lamp and battery life.
Typical of the consumer electronics market, inverters for portable products also face on-going
demands for ever-increasing efficiency to reduce heat and prolong battery life, while simultaneously
meeting size reduction and ever-lower cost models.
For many years, display makers employed a Buck/Royer inverter topology to strike and power CCFLs.
This analog power topology is essentially a combination of a step-down Buck voltage regulator and a
self-resonant Royer oscillator with an integral step-up transformer.To read more, and to learn about other types of inverter circuits besides the "buck royer" click the photo below.

Please take some time to visit our electronics repair website at http://www.preher-tech.com/. There are lot's of informational pages including more info on our company.You can also check out our certification program and join our news letter.Click the photo below to find out more.....

I want to share with you some of the places I like to buy my testing equipment.For the electronics repair man it is essential to have the right testing devices, but you do not always have to spend an exteme amount of money on a good device.For instance I love Fluke DMMs but a meter that exspensive is not necessary.Not to say you should buy a very cheap meter as that would not be good with poor accuracy.I prefer a medium priced DMM myself like the ones from Sinometer.....click here to see the DMM I use....It is also important to have a good analog meter for testing certain components, but you need to make sure and get the proper one with the needed ranges, you want to make sure that the resistance setting can go up to x10k.I like the Sunwa analog multimeter....click here to see the analog meter I use.Some other important tools are the ESR Meter which I have discussed before and the Ring Tester.Below I would like to share with you some places that I have found to be good sources for purchasing test equipment including all the meters I just discussed.Just click on the photos......

LCDs are rapidly becoming the most popular display technology.They are the most common type of TVs that I repair now.I myself own a couple, one for my living room and one for the computer.Below is some info on LCD technolgy...enjoy.

A liquid crystal display (LCD) is an electronically-modulated optical device shaped into a thin, flat panel made up of any number of color or monochrome pixels filled with liquid crystals and arrayed in front of a light source (backlight) or reflector. It is often used in battery-powered electronic devices because it requires very small amounts of electric power.Read more by clicking the photo below.......

Contact Bounce and De-BouncingThe DefinitionPush-button switches, toggle switches, and electro-mechanical relays all have one thing in common: contacts. It's the metal contacts that make and break the circuit and carry the current in switches and relays. Because they are metal, contacts have mass. And since at least one of the contacts is on a movable strip of metal, it has springiness. Since contacts are designed to open and close quickly, there is little resistance (damping) to their movement.
Because the moving contacts have mass and springiness with low damping they will be "bouncy" as they make and break. That is, when a normally open (N.O.) pair of contacts is closed, the contacts will come together and bounce off each other several times before finally coming to rest in a closed position. The effect is called "contact bounce" or, in a switch, "switch bounce".The ProblemIf all you want your switch or relay to do is turn on a lamp or start a fan motor, then contact bounce is not a problem. But if you are using a switch or relay as input to a digital counter, a personal computer, or a micro-processor based piece of equipment, then you must consider contact bounce.

I am receiving a new ESR meter and a ring tester from a friend of mine in Russia, Mike.The ESR micro v3.1 and the FBtest both are from his company "Radio Devices".After I get them and use them I will post a review.I am very excited to test try the ESR microv3.1, it has a nice range for testing capacitance.I have another capacitance meter for testing anything under 1uF(the low end of the esrmicro), but my problem with that meter was that I can only check up to 200uF at it's high end, with the ESR micro v3.1 I can test up to 60,000 uF!!It is also very compact Compared to my other ESR meter or Capacitance meter.I am also excited to try the FBtest and compare it with my other ring tester that I currently use.I will let you all know more once I test these units out for myself.

Thanks again to "Radio Devices" ,you are awesome Mike, please check them out for more info by clicking here.Click on the photos below for more info on the individual devices.

Capacitive Reactance.Learn how capacitors effect AC circuits. Click the photo or click here.

Most Common SMPS Problems,The following probably account for 95% or more of the common SMPS ailments:

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Supply dead, fuse blown - shorted switchmode power transistor and other semiconductors, open fusable resistors, other bad parts. Note: actual cause of failure may be power surge/brownout/lightning strikes, random failure, or primary side electrolytic capacitor(s) with greatly reduced capacity or entirely open - test them before powering up the repaired unit.
Supply dead, fuse not blown - bad startup circuit (open startup resistors), open fusable resistors (due to shorted semiconductors), bad controller components.
One or more outputs out of tolerance or with excessive ripple at the line frequency (50/60 Hz) or twice the line frequency (100/120 Hz) - dried up main filter capacitor(s) on rectified AC input.
One or more outputs out of tolerance or with excessive ripple at the switching frequency (10s of kHz typical) - dried up or leaky filter capacitors on affected outputs.
Audible whine with low voltage on one or more outputs - shorted semiconductors, faulty regulator circuitry resulting in overvoltage crowbar kicking in, faulty overvoltage sensing circuit or SCR, faulty controller.
Periodic power cycling, tweet-tweet, flub-flub, blinking power light - shorted semiconductors, faulty over voltage or over current sensing components, bad controller.
In all cases, bad solder connections are a possibility as well since there are usually large components in these supplies and soldering to their pins may not always be perfect. An excessive load can also result in most of these symptoms or may be the original cause of the failure. And don't overlook the trivial: a line voltage select switch in the wrong position or between positions (possibly by accident when moving the supply, particularly with PCs), or damaged.

This is a very important tool for any electronics technician.Capacitors(mostly electrolytic) are very often the cause of failure with many devices, these capacitors may seem fine when checked with the capacitance setting of your DMM or when checking them with the ohm settings of an analog meter, but These meters will not tell you the ESR or "Equivalent Series Resistance" of the capacitors being tested.The ESR may have become very high even though the capacitance checks within tolerance on a capacitance meter and the capacitor seems to charge and discharge fine with the analog meter, as a matter of fact this is very common.That is why the ESR meter is a necesary tool, not to say the DMM and analog meter don't have there advantages too, they are also necesary.You will need them to test for shorted capacitors(an ESR meter would see this as a good capacitor), to make sure the capacitor charges and discharges properly and to check a whole array of other components, a good tech has all the meters and tools of his trade to make him proficient in his job.Now lets take some time to discuss what ESR actually is.

click here to read the rest of this article......

Here are a couple of my favorite books from one of my favorite authors and a good friend of mine Jestine Yong.

Testing Electronic Components

How to Find Burnt Resistor Value

LCD Monitor Repair