I Turned This Broken Phone into a Mini PC!

Summary of Tech Concepts / Build Details

• Goal: Turn a broken Samsung Galaxy S9 (bought on eBay for ~$22) into a functional mini PC on a total budget of about ~$52 (including adapters, enclosure, wiring, and power parts).

• Core software platform: Use Samsung DeX instead of Windows. DeX converts the phone’s Android interface into a desktop-like UI when connected to a display.

  • DeX origin: Introduced around 2017 (Galaxy S8 / S8+), and the S9 is from the early DeX era.
  • Hardware approach (PC conversion):
  • Uses a 5-in-1 USB-C hub (about ~$12) providing USB + HDMI + power delivery, enabling video output and peripheral support.
  • Setup was straightforward: the display appears immediately, and input feels responsive.

Hardware Recovery / Modifications

Phone condition

• The phone had severe screen damage (flicker, color issues, partially failing panel).
• Touchscreen still worked, which was sufficient for the builder’s needs.

Battery heat + aging (main issue)

• The S9’s battery health is poor, showing visible drain.
• Charging caused noticeable heat, which can be problematic for long-running desktop/gaming use.
• Performance becomes inconsistent as temperature rises (lag/stutter).

Battery removal power method

• Removes the battery entirely and powers the phone directly through the battery contacts.
• Adds a voltage regulator board to supply stable, correct voltage for reliable operation without a battery installed.
• Powers an RGB fan from the same power source (via a Molex connector).

Power control

• Adds a simple power switch so the device can be turned on/off without unplugging power.
• Confirmed behaviors:
  • Instant shutdown
  • Normal reboot when toggling the switch

Enclosure (custom mini PC case)

• No ready-made case was found for a Samsung DeX setup, so the builder 3D-printed a custom enclosure.
  • Print cost: about ~$6
  • Design features:
    • Vented ends
    • Top panel held by magnets (no screws)
    • Internal mounting space for a small fan under the top cutout

Mechanical workarounds

• Reuses a phone clamp (from an old camera mount) to secure the S9 inside.
• Fixes a too-long USB-C connector using a U-shaped USB-C adapter (~$2.50) to route the cable neatly inside the case.

Performance / Testing Results

Resolution limitation (1400p / 1440p)

• The highest target attempted was 1,440p.
• DeX would not output 1,440p.
• The builder tried using Good Lock and searching settings, but lacked needed modules (missing MultiStar / DeX options).
• Conclusion: likely a hardware limitation (left unresolved).

Video playback

• Output is very smooth:
  • Near-instant scrubbing
  • Immediate playback start
• Tested 1,440p video with no noticeable stutter/lag or dropped frames.

Game tests (emulation via connected controller)

• Controller: Bluetooth pairing works quickly and reliably.

Gran Turismo 4 (PS2)

• Runs surprisingly well
  • Sometimes near ~60 FPS
  • Drops in heavy scenes to about ~25 FPS
• CPU often runs near full utilization.

The King of Fighters

• Generally smoother:
  • Typically around ~50 FPS with fewer drops
• CPU still stays fully active to maintain stability.

God of War II

• Much harder workload:
  • Hovering around ~33 FPS
• Suggests performance could improve by lowering rendering resolution, but it’s close to hardware limits.

PSP / Dreamcast

• Feels more comfortable (lighter workload).

Minecraft (1.7.10)

• Performance often exceeds ~200 FPS
• Sometimes around ~150 FPS
• Generally very smooth.

Key Takeaways

• The project shows that Samsung DeX + a USB-C hub can turn even an 8-year-old broken phone into a lightweight mini PC for:
  • Smooth video playback
  • Retro / older console emulation (with FPS varying by game demands)
• The biggest challenge was thermal/power stability, addressed by:
  • Removing the battery
  • Direct battery-contact power with voltage regulation
  • Added cooling (RGB fan)

Speakers / Sources

• Main source / speaker: Unspecified single creator (builder narration throughout the project and tests).
• Tech/platform referenced: Samsung DeX and Samsung Good Lock / MultiStar module.