This is an 250mW RF power amplifier project. This circuit is designed to amplify the output of about 7mW wide band FM transmitters to a final level of about 250mW.

Schematic Diagram:

Component Parts:

R1 ____________________ 10R
R2 ____________________ 470R
R3 ____________________ 47R
R4 ____________________ 120R
R5 ____________________ 2K2
R6 ____________________ 4K7
R7 ____________________ 22R
Q1 ____________________ 2N2369
Q2 ____________________ 2N4427
Q3 ____________________ 78L08

C1, C11 _______________ 10n
C2 ____________________ 220u/16V
C3 ____________________ 33p
C4 ____________________ 47p
C5, C6, C7, C8, C9 ____ 1n
C10 ___________________ 10u/25V
L1 ____________________ 5 turn coil
L2 ____________________ 3 turn coil
L3 ____________________ Ferrite
L4, L5, L6 ____________ RFC

This electronic circuit is a simple 2-transistor VHF power amplifier, with about 16dB gain, and requires no tuning or alignment procedures. Wideband techniques have been used in the design and the circuit is equipped with a “lowpass” filter to ensure good output spectral purity. The project has been designed for assembly on a single-sided printed circuit board. The circuit is specifically designed to amplify the output of 7mW to 10mW WBFM transmitters (wide band) to a final level of 250mW to 300mW, after the filter.

The kit of this power amplifier circuit is available at kitsrus.com. You may download the kit manual including the information of schematic diagram, component parts, and circuit works HERE

This simple 220V light dimmer circuit can be used to adjust the brightness of mains lights. It also can be used to adjust the speed of AC motors. It uses a triac, diac and has a radio-frequency interference (RFI) noise suppression circuit built into it as well.

Schematic diagram:

Component part:
R1 = 10K
R2 = 2K2
R3 = 180K
Potentiometer 250K
C1 = 150nF/400V dipped polyester
C2 = 47nF/630V  dipped polyester
C3 = 220nF/250V AC dipped polyester
Triac = 2N6075 or BT136-500D
Diac = HT-32
FUSE 2A or 3A

Download the circuit documentation of 220V/240V Light Dimmer. The kit of this circuit is available at kitsrus.com, please visit the website to purchase the kit.

This is a sound activated switch circuit. It’s will turn on and turn off based on a loud sound such as clapping your hands. You can adjust the sensitivity (how loud of a sound will activate the circuit) from a pin drop to a Mack Truck Horn. Very practical for a variety of projects. Add a relay to turn on a light when your dog barks, or set of a siren when an intruder makes a loud noise.

Here the circuit diagram:

Component Part:

PCB Layout:

Download the manual instruction about the sound activated switch HERE
This circuit kit available at http://www.electronickits.com/kit/complete/elec/ck1607.htm, go to that page to buy the kit.

This is a simple bridge amplifier based on TDA7240A. This circuit is designed for car audio system, but you may use this circuit for your small home audio application…

Schematic Diagram:

PCB Layout:

About TDA7240A:
The TDA7240A is a 20W bridge audio amplifier IC designed specially for car radio applications. The low external component count and compact Heptawatt 7-pin power package the TDA7240A occupies little space on the printed circuit board.

Reliable operation is guaranteed by a comprehensive array of on-chip protection features. These include protection against AC and DC output short circuits (to ground and across the load), load dump transients, and junction overtemperature. Additionally, the TDA7240A protects the loudspeaker when one output is short-circuited to ground.

Download TDA7240A datasheet for circuit reference.

Here’s the circuit diagram of a 70W stereo power amplifier which built using single power IC STA550. The circuit is very simple and require little additional electronic components to support the work of IC STA550.

With the features of this IC is owned, produced the audio output will not disappoint.

About STA550:
The STA550 is a fully integrated power module designed to implement a BASH® amplifier when used in conjunction with STABP01 digital processor.

Download STA550 Datasheet

This is a 220V LED flasher circuit which is intended as a reliable replacement to thermally-activated switches used for Christmas tree lamp-flashing. This a cheap circuit and easy to build.

Schematic diagram:

Component Parts:

R1_________ 100K
R2,R5______ 1K
R3,R6______ 470R
R4_________ 12K
C1_________ 1000µF 25V
D1-D4______ 1N4007
D5_________ SCR  P0102D
Q1_________ BC327
Q2_________ BC337
SK1________ Female Mains socket

How the circuit works:
The device formed by Q1, Q2 and related resistors triggers the SCR. The flashing frequency is provided by R1, R2 and C1. To change flashing frequency value, just  set C1 value from 100 to 2200µF, don’t modify R1 and R2.
Best performances are obtained with C1=470 or 1000µF and R4=12K or 10K. Due to low consumption of normal 10 or 20 lamp series-loops, very small and cheap SCR devices can be used, e.g. C106D1 or TICP106D.

Source: redcircuits.com

Below is a 80W amplifier circuit is constructed by using a power IC TDA7295. With a very simple design, makes this circuit very easy to build. TDA7295 has many features to support your audio system, the most important is that the IC has very low distortion and very low noise feature.

Schematic diagram:

PCB Layout:

Notes:

• Power supply voltage should not exceed 40V.
• Use stable and regulated power supply. The power supply should be has  minimum current output  2A.
• Use heatsink to prevent overheating on the power IC.

About TDA7295:

The TDA7295 is a monolithic integrated circuit in Multiwatt15 package, intended for use as audio class AB amplifier in Hi-Fi field applications such as home theatre and topclass TV. The wide voltage range and to the high out current capability make the TDA7295 able to supply the highest power into both 4W and 8W loads even in presence of poor supply regulation, with high Supply Voltage Rejection.

The built in muting function with turn on delay simplifies the remote operation avoiding switching on-off noises.

Download the datasheet document for yuor reference to optimize this circuit diagram.
Download TDA7295 datasheet

Fixing a cell phone is basically not a difficult thing. All you need is proper equipment, basic knowledge of electronics and of course a manual guide, including schematic diagrams. Nokia is one of the largest mobile phone manufacturer in the world. The products are very diverse, lots of types of nokia available in the market.

If you are a cellular telephone repairman, then you should have a service manual guide as complete as possible.

I’ve found a complete Nokia wiring diagram at 4shared.com. The files has been shared by someone there.
Here the links. There are divided in 2 zip parts. Use winrar to extract the files.
» Nokia wiring diagram part 1
» Nokia wiring diagram part 2

Note: I’m not responsible about the file, about the risk or another broken/damage caused. Use the files for your own risk.

The following is a quad amplifier circuit (amplifier with four inputs and four outputs) based TDA7381. This amplifier is designed for car audio system, but you can also use this circuit for other purposes. This circuit has a design very simple and very easy to build.

Schematic diagram:

PCB layout:

Top layout / component placement:

About TDA7381:

The TDA7381 is a class AB audio power amplifier in Flexiwatt25 package designed for car radio applications. You may use the circuit for another application such as mp3 player, computer etc. Thanks to the fully complementary PNP/NPN output configuration the TDA7381 allows a rail to rail output voltage swing with no need of bootstrap capacitors..

The extremely reduced components count allows very compact sets. The on-board clipping detector simplifies gain compression operations. The fault diagnostics makes it possible to detect mistakes during Car- Radio assembly and wiring in the car

Download TDA7831 Datasheet. All information about this circuit is provided in the datasheet.

Following is a circuit you can use to delay an electronic device to be disabled. For example, you can connect this circuit to the lamp in your room. When you turn off the lamp with a switch on the circuit, the lamp will remain lit in a certain period of time, before the lamp really switched off.

Electronic Parts:

How the circuit work:
Due to the low current drawing, the circuit can be supplied from 220Vac mains without a transformer. Supply voltage is reduced to 10Vdc by means of C1 reactance, a two diode rectifier cell D1 & D2 and Zener diode D3. IC1 is a CMos 555 timer wired as a monostable, providing 15 seconds on-time set by R3 & C4. When SW1 is closed, IC1 output (pin 3) is permanently on, driving Triac D4 which in turn feeds the lamp. Opening SW1 operates the monostable and, after 15 seconds, pin 3 of IC1 goes low switching off the lamp.

Notes:

• The circuit is wired permanently to the mains supply but current drain is negligible.
• Due to transformerless design there is no heat generation.
• The delay time can be varied changing R3 and/or C4 values.
• Taking C4=10µF, R3 increases timing with approx. 100K per second ratio. I.e. R3=1M Time=10 seconds, R3=1M8 Time=18 seconds.
• Low Gate-current Triacs are recommended.
• Use a well insulated mains-type switch for SW1.

This circuit using high voltage source. Please Make sure you use a safety device before trying to activate this circuit.

Source: redcircuit.com