Flyback Transformer-How to locate the ABL lineWritten by Jestine Yong
Whenever there is a complaint about monitor contrast problem i will check on flyback transformer ABL (automatic blanking limiter) circuit. Sometimes a weak picture tube might caused contrast problem. If picture tube is good, i will go straight to contrast circuit. The question is how do we find where contrast circuit located? Simple, if you have a datasheet for video pre- amplifier ic, definitely you can find contrast pin. For LM1203N video pre-amp ic contrast pin is located at pin 12. Replace this ic or trace from this circuit to find cause of contrast problem.
From experienced, usually capacitors shorted and resistor turned into high ohms were caused of problem. A video pre-amplifier can also be defective. To confirm whether is circuit or ic problem, just solder out contrast pin and switch on monitor. If monitor display normal picture (contrast ok) then suspect abl line circuit. If it remain same (dim contrast) replace video pre-amp will usually solve problem.
The contrast signal came from one of pin (leg) of a flyback transformer which we called it as abl pin. Many technicians have difficulty to trace abl pin because usually a flyback transformer consist of around 10 pins. Some pins are B+, GROUND, AFC, ABL, X-RAY PROTECT, VCC, to HOT, HEATER, horizontal centering and etc. But there is one and simple way that i'm gone to show you how to locate abl pin. Use two analog multimeters set to x10kohm range. Connect it in series (+ probe to - probe) and measure flyback transformer from anode (the red cap) to all of pins under flyback. You have to desolder all pin or just remove flyback from mainboard in order to get an accurate reading.
VoIP ExplainedWritten by Andrew Taub
Voice over Internet Protocol or VoIP, is one of today's hottest and most confusing new technologies. Because of all confusion and complexity, Teleco has written this page to inform and educate you. We hope you find it helpful. VoIP consists of 2 major technologies....
Making Calls Over Internet
This is most common use of VoIP. It is also called VoIP lines or trunks. If you have a high speed internet connection, like cable modem, DSL, or T1, you can use your high speed connection to make phone calls on internet. There are many companies like Vonage, Lingo, and VoiceWing (Verizon) that offer VoIP lines. Cable companies also offer VoIP lines, but only if you have their cable modem service. So, to boil it down, instead of getting your dial tone from Verizon over traditional phone network, you get your dial done from your internet company. Any phone system made (even an old one) can take advantage of VoIP lines. You do not need an IP based (IP PBX) or even IP compatible phone system.
The advantage of VoIP lines are:
Lower Bills. Usually you pay a flat monthly rate and all your calls in USA and Canada are free You can take your number with you. If you move around corner or across country with VoIP you can keep your existing phone number even if you move to a different area code. Multiple area codes. You can get phone numbers from different area codes or even overseas numbers. Portability. You can move VoIP router with you and take your service easily with you. You can even set it up to use your laptop and a WiFi connections to make calls from anywhere you can get high speed internet access. Features. VoIP lines come with Caller ID, Call Forwarding, and lots of other great features. The problems with VoIP lines are:
Quality is not as good as traditional phone service, but it's close and getting better all time. Set up can be very challenging. Depending on how fast your internet connection is, it may be possible to make several calls at same time over internet. However, more calls you make at once slower your internet connection will be and poorer sound quality of your calls will be. Faxes, modem, and alarm systems don't work well over VoIP lines. Sometimes they won't work at all. If you need a lot of lines, cost of high speed internet connection may outweigh savings. There are some minor technical issue using VoIP lines and Automated Attendants and Voice Mail systems. If your internet access goes down, all your phone lines go down too. VoIP lines normally don't work if power does out, but you can set up back up batteries. Right now Government does not tax VoIP service. If that changes VoIP may not be price effective anymore. Connection Remote Workers or Remote Offices....Voice over IP Stations.