Match the exact model, region, and branch name. Similar model numbers are not the same device.
Firmware files are here on Inar Guide. Tutorials, flash tools and USB drivers are on FlashGuideHub.
When Tunde’s Digma Citi Z400 3G (CT4024PG) tablet bricked during a routine app install—refusing to boot and stuck on the Digma logo—he turned to the firmware community for help. This “Community Hero” story documents how forum wisdom and precise flashing with the official V20170810 SPD firmware brought his device back to life.
User Experience: Tunde’s Tablet Crisis
👤 Profile
Tunde is a tech enthusiast in Lagos who uses his Citi Z400 for podcasts and online research. After his tablet froze mid-update, it never recovered. He posted his error logs on XDA Developers and 4PDA, prompting actionable community advice.
Firmware & Device Details
| Property | Value |
|---|---|
| Firmware Filename | Digma_Citi_Z400_3G_CT4024PG_20170810_SPD.zip (502 MB) |
| Build Date | 2017-08-10 |
| Key Files | CT4024PG_20170810.pac, preloader, system.img, nvram.img |
Specifications Verification
| Specification | Details |
|---|---|
| Model | Digma Citi Z400 3G (CT4024PG) |
| Chipset | UNISOC SC7731E (Quad-core 1.3 GHz) |
| RAM/Storage | 1 GB RAM / 8 GB Storage |
| Display | 8″ IPS 1280×800 |
| Android Version | Android 6.0 Marshmallow |
⚠️ Critical Warning
Flashing the nvram partition incorrectly will erase IMEI data. Always back up NVRAM before proceeding.
Required Tools & Drivers
- SPD Upgrade Tool R27.10
- Spreadtrum USB Drivers v4.20.0201
- Windows 10 PC, USB 2.0 cable (disable auto-driver install)
For a complete walk-through of the SPD flashing process, refer to our guide: How to Use the SPD Upgrade Tool to Flash Your Smartphone.
Flash Execution: Step-by-Step
- Uninstall Drivers & Reinstall:
- Remove existing mobile drivers, reboot into Safe Mode, install Spreadtrum drivers.
- Extract Firmware:
- Unzip to reveal
CT4024PG_20170810.pac; verify MD5 from community thread.
- Unzip to reveal
- Load Packet in SPD:
- Launch SPD R27.10 → Gear icon → Load Packet → select
.pac.
- Launch SPD R27.10 → Gear icon → Load Packet → select
- Configure Mode:
- In Settings → uncheck “Auto Format” → enable “Download Only” → save profile “CitiZ400-20170810”.
- Connect & Flash:
- Power off tablet, hold Volume Down, connect USB → tool shows “COMx” → click Start.
- Verify & Boot:
- Wait for Passed, disconnect, power on, and allow up to 3 minutes for setup.
Recovery Results
🏆 Success Metrics
- Boot Time: From 5 minutes to 40 seconds
- System Stability: No more random reboots or UI freezes
- Network Performance: Restored 3G connectivity with stable data
- User Feedback: Tunde reports 100% uptime during work sessions
Advanced Tips & Community Links
- Check XDA for custom kernels compatible with SC7731E for improved performance
- Explore 4PDA for regional CSC packs to enhance network compatibility
- Use
MhlNpToolto back up and restore NVRAM partitions
Share Your Story
Did this guide bring your Digma Citi Z400 3G back from the dead? Post logs, screenshots, and your unique fixes below to help fellow community members succeed!