The Complete Guide to Digma Linx A400 Stock Firmware

Download free stock firmware files, compare available builds, and use the matching flash guide before writing anything to the phone.

Brand Digma
Published October 13, 2022
Updated Sep 21, 2025
Read time 3 min
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Before you flash

Match the exact model, region, and branch name. Similar model numbers are not the same device.

Need flashing steps?

Firmware files are here on Inar Guide. Tutorials, flash tools and USB drivers are on FlashGuideHub.

The Digma Linx A400 is an ultra-budget smartphone released in 2016, designed for essential communication with its compact 4-inch display and 3G connectivity. Due to its very modest hardware (256MB of RAM), the device can become slow or unresponsive over time. For owners looking to restore this phone to its original Android 5.1 Lollipop performance, flashing the official stock firmware is the most effective solution.

This guide provides the official firmware package and a clear path to safely reinstalling the software on your device.

Digma Linx A400 Firmware Details

Below are the key specifications for this official firmware package:

Attribute Details
📱 Device Digma Linx A400 (LT4001PG)
🆔 Chipset Spreadtrum SC7731C
🤖 Android OS 5.1 Lollipop
🔢 Build Number 20160612
📂 File Type .PAC Firmware
💻‍💻 Flashing Tool SPD Upgrade Tool

Why Flash the Stock Firmware?

Reinstalling the official firmware is the best solution for a variety of critical software issues on the Linx A400:

  1. Unbrick Your Phone: Revives a device that fails to boot past the startup logo or is completely unresponsive.
  2. Restore Performance: With only 256MB of RAM, the phone is very susceptible to slowdowns. A full flash is the best way to clear system memory and restore its original speed.
  3. Eliminate Viruses: A complete flash is the most thorough method for removing malicious software from your device.
  4. Fix System Errors: Resolves frequent application crashes and other system-wide bugs that can occur on low-memory devices.

⚠️ Important Prerequisites

Before you begin, ensure you have the necessary drivers and tools. You will need to download the SPD Upgrade Tool and install the correct Spreadtrum (Unisoc) USB drivers on your computer. A full backup of your device data is also highly recommended as this process will erase everything.

Download Official Firmware for Digma Linx A400

  • File Name: Digma_Linx_A400_LT4001PG_20160612_SPD.zip
  • Size: 450 MB
  • 🔗 Download Link (Google Drive): Digma Linx A400 Firmware

How to Flash the Firmware

This device’s firmware is a .pac file and must be installed using the SPD Upgrade Tool. Here is a summary of the main steps:

  1. Download and extract the firmware and required tools.
  2. Install the correct Spreadtrum (Unisoc) USB drivers on your PC.
  3. Launch the SPD Upgrade Tool and load the .pac firmware file.
  4. Power off your Digma Linx A400. This model has a removable battery, so taking it out for 10 seconds is recommended to ensure a full power down.
  5. Connect the device to your computer while holding the Volume Down key to initiate the flash.

For a complete, step-by-step tutorial with screenshots and troubleshooting, please follow our master guide:

→ How to Use the SPD Upgrade Tool to Flash Your Smartphone

Disclaimer: Flashing firmware carries inherent risks. If instructions are not followed precisely, it could damage your device. We are not responsible for any data loss or damage. Proceed with caution.

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