Shahriar

Hi I have Uploaded a Video Aid Project which I have downloaded from SILICON Chip Website. I think it will help you with what you are going to do. Download it from here http://www.4shared.com/file/9112625/a494a2d5/Video_Aid.html Shahriar

Hi I want to build a Big, High quality Loud Speaker But I do not Know how to choose a high quality speaker for it. I mean How can I determine if a speaker is good or not? Choose it by model? (JVC, Pioneer, ...) choosing by magnet? choosing by diaphragm meterial? How? ThanX in advance Shahriar

Good Points ;) ThanK you very Much for Your reply. Also take a look at this site. It is really fun. Althoght you may have seen it before. ::) http://www.linkwitzlab.com In fact I do not understand very much from those equations, But I really enjoy the Pictures ;D Specially: http://www.linkwitzlab.com/Pluto/photos.htm http://www.linkwitzlab.com/orion_us_examples.htm Shahriar

I know two Kinds of Hall Effect sensors... One type are a Switch like UGN3113 that if they sens a specific value of Flux they switch on a Open-Collector Output. The other type are Linear like UGN3503 that their output is a linear voltage depending on Sensed Flux. Maybe this can help you to solve your problem HTH - Shahriar

Hi Look at this LoudSpeaker http://www.roundsound.com/reference-3-speakers.htm Two Things are dark to me: 1- Is the back of those Speakers Open or Closed. Specially the Woofer? If they are closed, Are they sorrounded with the Round Cabinet or there is a air way between the cabinet and The Main Black Chasis? 2- The two small one Speakers seems to be the same? are they really the same or One of them is Tweeter and the Other one is a midrange? or they are the same but with different Cross-Over circuits? ThanX in advance Shahriar

Dear Audioguru ThanX for your reply. The Maximum Output swing of this opAmp is Vcc/2. i.e. If +vcc = 22V the Maximum Swing will Be 11V Because of R3 & R4 WHich Are equal and provide a Voltage devider. Am I right?

Hi I was Looking in Audio Project section and I encountered with this Project (Motorola Hi-Fi Power Amplifier) http://www.electronics-lab.com/projects/audio/041/index.html Something is strang to me. The output voltage is always equal to OpAmp Output. The Maximum output Swing for Opamp is limited with R3 and R4 to (Vcc/2 - 0.7V) . So the output power will be 1/4 of the Rated powers in Table, which I think is calculated with respect to Maximum swing of Vcc. 1- Tell me if I am wrong. 2- What better OpAmp do you know with Maximum Vcc of +-30V (741 is a little bit Old) ThanX Shahriar

Hi I want to build a system for a big Hall. If I use a usual 2-Speaker cd-Players and at one end of the Hall, People dancing at the other end of hall, do not receive enough power. What is the best topology to use. I mean How many speakers? Where to put them? and ... (what Topology they use in discos to cover all people? this may can help me!!!) ThanX Shahriar

Dear Audioguru what is your first choice for a 30-50W Power Amplifier If you want to build a audio System for yourself. Are STK amplifiers good or do you know any better Power Amplifier ICs (or descret). What do you recommend? ThanX Shahriar

ThanK you for your reply What is the practical way to measure a Power amplifier Distortion? ThanX Shahriar

Last year I built this project for one my friends. Look at the attached files I also attached a SILICON CHIP files too. But I couldn't find the sensors in this project. Just remeber to keep the sensor some where to protect it from Lamp Light. Otherwise you will receive a 50Hz pulse at output although some filters have used to remove it. I used the sensors on both sides but silicon put them in one side. HTH - Shahriar HearRate_Monitor_Schematics.rar SILICON_Heart_Rate_Monitor.rar

Hi I have designed this power amplifier. I think it is a little bit different with Normal PA, because I have tried to use two Voltage-Current converter to drive power output transistors to reduce zero-crossing. I have attached the schematic to tell me anything wrong about the topology I have used. I have not draw all things needed in details. Just about Topology. Let me explain a little more: the Input signal will be converted to Current around U1A and U1B. (one Sink current and one Source current) a feedback is there around R7 & R13 to set the total gain about 40. 1- if the input voltage is greater than zero U1A and q3 sink current from the base of Q1. I(sink) = Vi/R5) 2- if the input is negative U2A and Q2 source current. Isource = Vi/R7 3- U2A veries the voltage to control the output current through speaker. The Marked resistor values (R5 & R8) will be determined depending on desired Output power and speaker ohms. ThanX in advance Shahriar CurrentPA.pdf

Hi 1- How is the quality and distortion in Class-D amplifiers in compare with usual Class-AB PA? 2- How is the Power efficiency in Class-D amplifiers in compare with usual Class-AB PA. As I remeber efficiency in Class AB was something around 78%. How about class D ThanX Shahriar

Hi I found this link amazing. Hope U like it. http://www.inventgeek.com/default.aspx Shahriar

Hi I am new to LCD monitors (but Have lots of experience with CRTs) and I want to take my skills to the next level. I would apreciate it if You could guide me through some training documents to start LCD Monitors diagnostics. ThanX in advance Shahriar

Hi One of my friend has uploaded a Plasma TV training document for me to a free site. But unfortunately the damn proxy-serverds do not let me download it. I will apprecaite it If anyboady could download it and Upload it some where or email it to me. It will expire within 6 days. here the link http://www.yousendit.com/download/QRgOCY4vz4N5TA%3D%3D and my email [email protected] ThanX in advance Sahriar

Dear jomiservice ThanK you very much for your articles. they are very useful for me. shahriar

Hi I want to know if anybody has any Plasma circuit description document or any Plasma training document. or any link to download. There are lots of service manuals on th web but as U know there isn't any circuit description in service manuals. ThanX Shahriar

Dear $@$ sometime ago I decided to build a line follower robot by a small camera.( Not a Web cam.) I had decided to detect between the black Line and the white background by proceesind the video sinal. and to position it by other pulses in a component video signal. U should have enough information about a video signal to understand what I mean. Although i didn't the job, But I still think it is possible to do such thing very easily. It has many benefits to using a sensor. meybe u can use suck tricks to recognize wall depending on your conditions. HTH - Shahriar

Hi I want to build this Active 3-way cross-over circuit. But I do Not kow how to choose Power amplifiers. Here the problems: 1- If I choose a 15W subwoofer and a 15W STK power Amplier (STK4121) for it then what kind of Midrange and tweeter will be needed? Does it mean I have to choose a 15w Midrange and a 15W tweeter? 2- Should the gain of all PA be the same? i.e. if the Midranges are 8Ohm and Subwoofers are 4Ohm, how to choose the gain of PA? ThanX in advance Shahriar

Dear mvs sarma Thank you very much i will check it out. BTW, don't you have any Idea about Over Voltage protection? Dear Ante. You are right, maybe many of them don't worth to repair, but many of them has just a bad diode bridge or a blow up cap. and repairing of them takes about 20 minutes. 8) thanX Shahriar

Hi, ThanX both of you, I Understood it now. ;D But what is the roll of L6 there? Shahriar

Hi I am trying to repair Some ATX power Supplies.but some of them do not have ordinary faults. Most of them are in these two categories. 1- The computer assembler told me that with this bad PS, computer is working well but after a while (i.e. 10 Minutes or more) it will resets. but when they have replaced the ATX power supply, the problem was solved. Where should I look for this problem in ATX? 2- Some ATX power supplies will cause the mother board to fail. I was wondered to hear this because of the Over Voltage Protection circuit in ATXs, but I think maybe the Factory has removed those circuits. My question: Is it possible such thing in case of a OverVoltage protection circuit? 3- When I repaired an ATX, how can I test whether Over Voltage protection (OVP) circuit works to prevent MotherBoard Failing? ThanX in advance Shahriar

Hi Look at the this OLD ATX power supply. Can somebody explain how the 3.3V regulatosr built around TL431 IC works. It looks like a Shunt regulator but very strange. I know How TL431 works but can't understand this circuit. i.e. if Q13 Current changes, how does this affect 3.3V rail. (look at R71) http://www.4shared.com/file/4564161/afd71557/atxps.html ThanX Shahriar

Look what another guy has said about this topic: ESR is usually something to be minimized in a capacitor. However, where the original design depended (probably by accident) on a certain ESR, this may not always be the case: (From: Lee Dunbar ([email protected]).) Substitutions of low ESR caps into circuits which had lousy caps is not always the good idea that it appears to be.... Caution is advised, as low ESR caps will not limit surge currents. The circuits' series impedance drops (compare substituted capacitors ESR when new with the original capacitor's ESR was when it was a new capacitor), which, in turn, lets the surge magnitude rise, the higher currents destroy can semiconductors and other components. I guess what the industry needs is a good capacitor cross reference guide for aluminum electrolytics!