Rock Star Phone Repair Shop

Welcome To My Shop.
(1)

20/09/2025

iPhone 17 Air
Power Button

17/09/2025

CNC Code Formular

17/09/2025

60-Watt Darlington Transistor Amplifier: Power, Simplicity, and Analog Excellence

If you're passionate about building high-power audio amplifiers with discrete components, this 60-watt Darlington transistor amplifier is a perfect blend of performance and elegance. Designed for robust audio output, it uses the Darlington pair configuration to deliver clean, powerful sound—ideal for home audio systems, guitar amps, or DIY speaker projects.

At the heart of this circuit are TIP142 (NPN) and TIP147 (PNP) Darlington transistors, which provide extremely high current gain. These are paired in a Class AB push-pull output stage, allowing efficient amplification with low distortion. The Darlington setup boosts the base drive, enabling the output transistors to handle large currents while maintaining stability.

The input stage uses two 2N5401 PNP transistors in a common-emitter configuration to amplify the weak audio signal. This stage is coupled via a 10µF capacitor and biased with resistors (22kΩ, 1kΩ) to set the operating point. A 47pF capacitor helps stabilize the circuit against oscillations.

Key design features:

±33V power supply provides ample headroom for high-voltage swings
Emitter resistors (0.33Ω, 5W) ensure thermal stability and prevent runaway
Biasing network with 100kΩ and 33kΩ resistors maintains proper quiescent current
Zener diodes (4007) provide voltage reference for stable biasing
Output coupling capacitors (100nF, 100µF) block DC and pass only AC audio
The circuit delivers 60 watts RMS into an 8-ohm load, with excellent linearity and low noise. It's built for reliability, featuring protection against short circuits and overheating through careful component selection.

This amplifier showcases the beauty of analog design—no ICs, just transistors, resistors, and capacitors working together in harmony.

For more high-power audio builds, visit my site .

17/09/2025

Voltage Regulator Circuit Schematic

17/09/2025

မီးခုံနှင့်အတွင်းပိုင်းတပ်ဆင်ပုံ

17/09/2025

VU Meter Using LM324: Visualize Your Audio Levels with Style

If you're into audio projects, music, or DIY electronics, this VU (Volume Unit) meter using the LM324 quad op-amp is a fun and educational build that brings your sound levels to life. It’s a simple yet effective way to visually monitor audio signal strength—perfect for guitar amps, mixers, or home studios.

The heart of this circuit is the LM324, a popular quad operational amplifier IC known for its low power consumption and excellent performance in battery-powered applications. Here, it’s used in comparator mode to drive a series of LEDs that light up progressively as the audio input increases.

The audio signal enters through a 33kΩ resistor and 50kΩ potentiometer, allowing adjustable sensitivity. The signal is then fed into a chain of six non-inverting comparators, each set to trigger at a slightly higher voltage threshold. These are created using 1kΩ resistors and 330Ω current-limiting resistors for the LEDs.

As the input signal rises, each comparator turns on one by one, lighting up the corresponding LED—creating a classic "bar graph" display. The colors (red, yellow, green) indicate different volume levels: red for high, green for normal, and so on. This visual feedback helps prevent clipping and ensures optimal sound quality.

The circuit runs on just 6V DC, making it ideal for portable or battery-powered setups. The LM324’s internal structure allows all four op-amps to be used efficiently—three for comparison, one as a buffer or reference.

Key features:

No microcontroller needed – pure analog design
Easy to build and customize
Adjustable sensitivity via the 50kΩ pot
Low cost and compact
This project is perfect for beginners learning about op-amps, comparators, and audio signal processing. It's not just a meter—it’s a cool visualizer that adds style to any audio setup.

For more audio circuits and tutorials, visit my site .

17/09/2025

220V AC To 12V DC

17/09/2025

AC 220V input to AC 110V output, likely for voltage reduction.
It utilizes two components labeled "Suppressor capacitor" connected in series.
The circuit is designed to step down the AC voltage from 220V to 110V.
The components are rated for 250V~, indicating their suitability for AC circuits.
The wiring shows a clear input and output, with the suppressor capacitors playing a role in the voltage conversion process.

17/09/2025

Simple Electronic Code Lock Circuit: Secure Your Space with Digital Logic

If you're looking for a smart, low-cost way to secure a drawer, cabinet, or small door, this simple electronic code lock circuit is a fantastic DIY project. Built around the CD4017 decade counter IC, it’s a clever application of digital electronics that uses just a few components to create a functional keypad-based access system.

The CD4017 is a Johnson counter that sequentially activates one of its ten output pins (Q0–Q9) with each clock pulse. In this design, it's used as a digital comparator—when the correct sequence of button presses matches the preset code, the relay activates, unlocking the mechanism.

Here’s how it works:

Ten push-button switches (S1–S10) represent digits 0–9.
Each press sends a signal through a diode (D1–D9) to trigger a clock pulse on the CD4017.
The clock input (CLK) is controlled by a 555 timer or manual pulses via R2, R3, and C2.
A reset switch (S10) clears the counter if an incorrect code is entered.
When the right sequence is pressed, the Q10 output goes high, turning on transistor T1 (SL100), which energizes the 12V relay (RL1).
The relay can control a solenoid lock, alarm, or even a light—making it versatile for various security applications.

Key advantages:

No microcontroller needed – perfect for beginners
Low component count – easy to build and debug
Adjustable code length – change the logic to set a 3-digit or 4-digit code
Built-in reset function – prevents lockout
This circuit is ideal for students, hobbyists, or anyone wanting to learn about sequential logic and digital circuits. It’s not just a lock—it’s a hands-on lesson in state machines and timing.

For more DIY security projects, visit my site .