External Audio Amplifier for TV

This is an External Audio Amplifier.Its input is fed from a TV's Audio Out. customer wants this amplifier used to drive a speaker fixed in hotel bath rooms so the visitor can listen audio from the TV .and also they can controll the Volume of speaker by adjust a seprate volume control near the speaker. it uses a stereo signal cable and power for this unit. The volume control is used in Out put section , using multi position selector switch with proper resistor network.

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Transistor numbers and codes

Most transistor markings follow one of these codes: JEDEC, JIS or Pro-Electron. For ICs, look for known numbers (e.g. 741, 4001, 7400) between the prefix and the suffix. Don't confuse it with the date code. ICs typically have two numbers: The part number and the date code. 1. Joint Electron Device Engineering Council (JEDEC) These part numbers take the form: digit, letter, sequential number, [suffix] The letter is always 'N', and the first digit is 1 for diodes, 2 for transistors, 3 for four-leaded devices, and so forth. But 4N and 5N are reserved for opto-couplers. The sequential numbers run from 100 to 9999 and indicate the approximate time the device was first made. If present, a suffix could indicate various things. For example, a 2N2222A is an enhanced version of a 2N2222. It has higher gain, frequency, and voltage ratings. Always check the data sheet. Examples: 1N914 (diode), 2N2222, 2N2222A, 2N904 (transistors). NOTE: When a metal-can version of a JEDEC tra...

Ring tester

In my Electronic repair job I found normal multimeter is somewhat limited in certain area. so special tools are needed for saving a lot of time Ring tester is one of this kind .helping me to check small hi Q inductors SMPS transformer, TV Deflection coils ,LOT ,line driver transformer and almost any inductor working on hi frequency.Normal multimeter can only identify a open coil ,but not a shorted windings. I found some commercial available ring tester. but it is not available in local shops of my area.also it seems priced high. So I decided to make a ring tester of my own. Below is the one I successfully made from the junk box components. I found it very useful. and now it is one of my best test tool collection. Two Ic's, few LED's ,one plastic container and few resistors made this wonderful tool. If we test it with primary of SMPS transformer or LOT windings of a good one shows all its LEDs will light. depending on the inductive reactantce...

Boot Menu Option Keys

Below is a list of PC brands with their corresponding hotkeys for the boot menu and BIOS option. Computer Manufacturer Type Model Boot Menu Key BIOS Key ACER SERIES ACER Esc, F12, F9 Del, F2 ACER netbook AspireOne, Aspire Timeline F12 F2 ACER netbook Aspire v3, v5, v7 F12 F2 ASUS SERIES ASUS desktop F8 F9 ASUS laptop ...

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