San-Francisco-Chronicle-preher-tv

Just wanted to share that we got our letter in the mail the other day and I'm proud to say Preher-Tech is a Google favorite place. Check us out on Google today. Click on the photo below.

Have you ever wondered what Ripple Rejection Ratio is?
Ripple Rejection Ratio or Power Supply Rejection Ratio (PSRR) is a measure of
how well a circuit, component or Power Supply rejects ripple coming from it's input
at various frequencies and is very critical in
many RF and wireless applications. In the case of an LDO(Low Drop Out Regulator),
it is a measure of the output ripple compared to the input
ripple over a wide frequency range (10 Hz to 10 MHz is
common) and is expressed in decibels (dB).

Read more by checking out this PDF file. Or click on the photo below.

If you are an electronics repair specialist or just an electronics hobbyist interested in learning more about SMPS repair you must get this e-book. "Troubleshooting & Repairing Switch Mode Power Supplies" is the latest edition to Jestine Yong's series of excellent electronics repair books and I have to say this one is my favorite so far, It explains all the major circuits of the SMPS, how to identify all the major components, troubleshooting and testing methods plus so much more! This is the essential reference to anyone interested in learning SMPS repair. If you are a professional in the field of electronic repair like myself, then this book will help you big time, because as you know a large percentage of electronics equipment failures are related to the power supply and a large majority of electronics devices today use an SMPS. Don't hesitate check out this great book today, I highly recommend it.

I went out on a service call today for a Hyundai LC-23Y18, TV had standby light and when you tried to power the unit on the standby light would start flashing. As usual I checked all the Electrolytic capacitors in the SMPS first thing and sure enough like usual I found a capacitor with a high ESR. It was a 470uF capacitor on the secondary side of the standby switching transformer. The capacitor had an ESR of 7. After replacing the capacitor the TV worked like new. You can see I am very often replacing electrolytic capacitors in these LCD TVs and that is why I always check the Electrolytic capacitors in the SMPS first thing because so many problems can occur when these fail. That is why it is so important to have a good ESR meter if you want to do electronic repair, electrolytic capacitors are everywhere not just in the SMPS circuits.

A customer dropped off a Samsung SyncMaster 204T monitor for repair earlier this week, the display flickered and then went dim. He was told by his "computer guy" that the monitor needed a new CCFL. I told the customer I would look at it and that I thought it was more likely to be an inverter circuit issue. After opening the monitor as usual the first thing I did was look for loose connection and bad electrolytic capacitors on the SMPS board(bad electrolytics cause all sorts aof problems and are often the cause of failure), in this case the SMPS and inverter are integrated into one board. Right away I found that 2 secondary filter capacitors in the SMPS that had an ESR of 6 ohms and had changed value from 820uF to 10uF. Both capacitors had a max working voltage of 25V. After looking over the rest of the monitors circuits and checking the components in the inverter circuit I found no other problems. I re-soldered the HV transformers and MOSFET ICs in the inverter circuit as there was a few pins on the ICs with ring cracks as well as the HV transformer pins. I replaced the 820uF 25V capacitors and put the monitor back together. After setting it up and turning it on it was as good as new.I called the customer and told him he could come pick up his monitor. The customer was very pleased and the service charge was only $60. Hope this helps some of you they may come across one of these monitors with the same problem.

We have started a video tutorial on LCD TV repair, we will do one video every 1-2 weeks. Here is the first video which is an overview of all the major circuits within the LCD TV.

I have spoke of this book before, but I wanted to mention it again as it is such a great e-book. If you would like to learn LCD monitor repair than you need to take a look at this book. The author is Jestine Yong a great friend of mine and a master at electronics repair. Take a look at LCD Monitor Repair today.

Click here.



More titles by Jestine Yong, How To Find Burnt Resistor Value and Testing Electronic Components.

Cool video I saw on Jestine Yong's Blog today, decided I would share it with you.

Here is a great reference manual for you to print out and add to your collection.

Linear & Switching Voltage Regulator Handbook

Here is a great video on transistor biasing, Enjoy.

Have you seen the Preher-Tech Tools and Tips page? If not check it out today, here are a few of the great links you will find there.

Understanding Switch Mode Power Supplies
Identifying Television SMPS Problems
Algebra Course
Understanding The TV Horizontal Output Stage
Soldering 101
Practical Transformer Handbook
Capacitor Tutorial
Understanding Transistors

Got to the tools and tips page by clicking here.

Here are some more certifications, all of these are related to computers. Take a look maybe one of these will be one you can take and help boost your resume.


Computer Technician Test

Computer Skills Test

DOS Test

Microsoft Office Access 2007 Test

Click Here to see more.

Getting an electronics certification not only makes you feel great about all you have learned and accomplished, but it also let's employers, friends and family see that you really have what it takes to be professional in the electronics field. It will give you a great sense of pride that will motivate you to do better at your job and to continue learning and achieving even more certifications.

Here is a great place to get some electronics certifications. These are not easy tests and I suggest you study before trying to take one.

Basic Electronics Test

Integrated Circuits Test

Amplifiers And Filters Test

Analog Electronics Test

See all tests and pricing by clicking here


Also the C.E.T.G. offers electronics technician courses and certification.

C.E.T.G.

Apprentice Test

Journeyman Test

Master Technician Test

Here are a few cool links for people who need help repairing or modifying their game console, enjoy.

Video Game Console Repair

Wii Repair

Check out our latest youtube video.

Hello again from the office of Preher-Tech. It is getting pretty cold here in Medford Oregon, time to stop drinking the iced caramel mocha's...LOL. Halloween is coming soon, so I thought we should do a Halloween project. Here is my Jack O Lantern Light/Flasher. The video doesn't perfectly capture the way the LED's flash but you get the idea. Hope you enjoy and if anyone wants the schematic just email me john@preher-tech.com.

This is an awesome place to get parts. I have used this company in the past and have had nothing but great results. Take a look at Shop Jimmy today by clicking this link. Also read this article at "the star tribune" about the owner Jimmy Vosika and also a look into how things are done over at Shop Jimmy.






Shop Jimmy is going to give away a FREE refurbished flat screen TV, as soon as they hit 1,000 followers on there Twitter account, so follow Shop Jimmy today and tell everyone you know to follow them as well.

Here is some good info on making a better linear voltage regulator then the shunt type Zener Diode regulator in the last post ,with the addition of a NPN BJT the circuit becomes a much more efficient series regulator. Click here to read more.

Here is a cool article on using a zener diode and resistor to make a simple voltage regulator. This is a basic shunt regulator. Click here to read the full article.

I really like this magazine every month it contains lots of good information on electronics and cool project ideas. This month in the article "Properly Selecting Electronic Components, part 2" there was a lot of good information on components, tools and good electronic theory info including formulas for construction of your own capacitors and inductor's, plus other classic electronic formulas and facts. This is a really good magazine that everyone can enjoy and learn from.Thanks Nuts and Volt's and I hope you continue to put out awesome magazines every month for years to come. Click here to find out more about this great magazine or click on the photo below.

The Preher-Tech tools and tips page has recently been updated and lots of new info has been added and we will be adding a lot more shortly. Click here to go to the tools and tips page now and start reading all the recently added articles. All this info is specially picked out for those in the electronics repair field or those just wanting to learn more about electronic theory. Enjoy.

This is an important topic, all good technicians not only need to know what a transformer is and what they look like but also need to understand the theory behind how they work. It is also good to understand the different types of construction and there applications. There is a lot more to transformers than you may realize.



A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors — the transformer's coils. A varying current in the first or primary winding creates a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the "secondary" winding. This effect is called mutual induction.
If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will be transferred from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (VS) is in proportion to the primary voltage (VP), and is given by the ratio of the number of turns in the secondary (NS) to the number of turns in the primary (NP). To read more click here and here.

Just wanted to inform all my news letter subscribers that this months news letter is delayed until the 14th. I apologize but repair work has been very good , I keep getting influxes of LCD repairs. I want to make sure my book is ready before releasing the news letter and did not have enough time to finish the book yet. Thanks for understanding. I will be updating the Blog with lots of good info until then though so stay tuned.

Here is the ESR-micro v3.1 I had told you was being sent to me in a past blog. Well it is here now and I have done a review on my website.To see the review click here or click on the photo below. I have to say I really love this meter as it is so small, well made and also it checks capacitance and has a large range too 1uF-60mF(60,000uF). This meter will be getting a lot of use from me and we will see how it stands the test of time.

Recently one of my news letter subscribers wrote me looking for some information on testing BJTs, so I thought this would be a good topic for the Blog. Here are 2 links to some good information on testing a BJT , click here for link 1 and click here for link 2 you can also click on the photo below.

Don't forget to sign up for our FREE monthly electronics news letter, if you have not already signed up do it now by clicking here. Every month Preher TV will send out a news letter packed with electronics information and August's news letter will also be the release of my new book on electronics repair including LCD TV repair. Don't miss out, again if you are not a subscriber start today by clicking here or by clicking the photo below.

The third part on making electrical measurements. Click here to read part 3. These three articles just touch the surface, to learn much more about making measurements and testing electronic components you must read a good book on the subject, like "Testing Electronic Components" or "Electronic And Electrical Servicing", these are great books and by reading them not only will you have gained great amounts of knowledge but you will also have completed the first 2 necessary steps towards getting a CETG apprentice certification.

Second part of Making electrical measurements.Click here to read more.

Here is part one of a good article for taking electrical measurements, this is something you should feel very comfortable doing if you want to be an electronics repair technician, if you want to feel comfortable it is essential you know what you are doing..Click here to read more.

Beware of blue star international components, I have used them in the past with no problems, but I usually don't because they are over priced. This time I made an order because my normal distributor did not have the part I needed in stock and I needed it fast. Well guess what? These guys sent me a used refurbished convergence IC, it looked like it was pulled from a junk pile!!! it had rust on the back even!!! And guess what, it didn't work, I had to order another one from some where else to fix this customers set, and refund the customer the express shipping on that used part.I have emailed blue star international components asking them how they will resolve this and why they would send me this horrible used part when I was purchasing a new one, they have failed to respond and chose to ignore me. Oh well my business will never use this horrible company again, and I urge any of you that use this company to be aware they are using bad and illegal business practices. Be careful of anywhere you buy parts and stick with your trusted distributors.

Don't use these guys they do bad business, BEWARE!!!!
http://www.bluestar-online.com/


(Edit 7/30/09)
Well I have to say that although I have never received a response from Bluestar , I did notice today that they refunded me the money for the IC, when checking my bank account. I'm glad they refunded my money but it really does not excuse selling that "rebuilt" STK393-110.

Here is the Schematic and the parts list for the "Astable DJ" circuit featured on our project page recently.Visit the project page by clicking the photo below.

Here is our latest recycling project, using broken electronic devices from around the shop.This is a simple astable mutivibrator using variable resistors for an adjustable time constant.The parts list and schematic will be available soon on our project page, click here to visit the project page.Enjoy the video clip.