Wednesday, December 30, 2009

We are a Google favorite place!

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.

Friday, December 25, 2009

Ripple Rejection Ratio

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.



Power Factor Correction

I have a friend that is a fellow TV repair man and he was having some trouble understanding power factor and power factor correction. I suggested he read the "Power Factor Correction Handbook" by ON Semiconductor and I also wanted to share it with you guys as well. These guides are great and by reading this book you should have a general understanding of power factor correction. Click on the picture below to download this great book for free.




Wednesday, December 23, 2009

Power Supply Repair Guide

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.




Wednesday, December 16, 2009

Electronic Repair News Letter

If you missed the Preher-Tech News Letter in 2009, then now is the time to subscribe and get all our great electronics repair tips for 2010. Join now and receive 12 free electronic repair articles, one each month for the year of 2010.

Tuesday, December 8, 2009

LCD TV Repair

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.

Sunday, December 6, 2009

LCD Monitor Repair

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.