1.5V and 9V Battery Tester

Here is the circuit diagram of battery tester designed by Matthew B.. This circuit can be used to measure the 1.5V and 9V battery. The circuit is very-very simple and very easy to built since it uses five resistors and a panel meter only, and of course it is inexpensive too. Components List: R1 =… Read More »

Adjustable Sine/Square Wave Oscillator

The following scheme diagram is the circuit diagram of simple easily tuned / adjustable sine and square wave oscillator. With this circuit you can easily generate sine/square wave which can be adjusted both the frequency and amplitude. The circuit uses IC LM101A, a general purpose operational amplifier (op-amp) and IC LM111, a high-speed voltage comparator… Read More »

NiCAD Battery Charger with Current and Voltage Limiting

The following diagram is the schematic diagram of Ni-CAD battery charger circuit which featured with current and voltage limiting to keep the battery lifetime. The lamp L1 will be light brightly and the LED will be out when the battery is low and battery charging in progress, but the LED is very bright and the… Read More »

Tube Distortion Pedal

The following circuit is tube distortion pedal for guitar effect. The circuit designed by Ron Black. Circuit Notes: IC1 : 747 dual op-amp, other ICs may be substitued but pinout will different. You should check the datasheet IC2 : LM340K-12V Voltage Regulator All resistors are 1/2 W Bridge Rectifier – Full wave bridge recitifier, 50… Read More »

2 x 5W Stereo Audio Amplifier based TA7227 + Tone Control

The following circuit is a 5W stereo audio amplifier, built based on single amplifier IC TA7227. The TA7227 can be used for dual mode (stereo amp) and single mode (bridge connection/mono amp). This IC type featured some circuit protection: thermal protection, over voltage protection, current limitter and BTL DC short connection. The tone control circuit… Read More »

200mA/Hour – 12V NiCAD Battery Charger

The following diagram is the schematic diagram of 12V NiCAD battery charger with charging rate of 200mA/Hour. Components List: Resistor: 1 K Ohm, 68 Ohm, 2 K Ohm, Potensiometer 10K Ohm Diode: IN4001, 2x Zener IN752 Transistor: 2N2219, 2N2222

Tube Mic Pre-Amp

The following diagram is the circuit diagram of tube mic pre amplifier 12AX7. This circuit is little hard to built. You must have an intermediate or advanced skills to build this circuit. All capacitors with value of 33uF are 16V, while the all others are 50V unless marked otherwise. Resistors marked with “#” are 1%… Read More »

Electro-Harmonix Big Muff Pi Effect

The following diagram is the schematic diagram of electric guitar effect: Electro-Harmonix (EH) Big Muff Pi. The EH Big Muff Pi effect circuit would probably be better making the change by a modern input-jack power and a DPDT bypass switch. The types of transistors and diodes are unknown. It is likely that any high gain… Read More »


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