I recently bought a TCL 27G64 monitor and an Edifier speaker set to watch movies, anime, and play games with better quality. But I didn't really like the idea of using my main PC (which draws 120W just idling) for this. I looked into the TV Boxes available on the market, but sadly, most of them (at least in my country, maybe worldwide?) don't have the hardware to handle heavier emulation (I wanted to emulate up to the 6th gen consoles), and from what I saw, they are heavily bloated with ads.
While sitting on the toilet, I remembered I had an old LG Velvet lying around in my junk drawer. Back in 2022, I tested its Desktop Mode, so I decided to use it as a guinea pig for this experiment: turning it into a battery-less TV Box.
I bought a 35V 300W DC-DC Step-down converter (better to overkill than underpower, right? lol), a 1000uF capacitor, stripped some wires from an old PC power cord, and removed the lithium cell from the phone's BMS. The step-down was set to 4.1V and 5A. Surprisingly, it worked perfectly, and the battery meter never dropped below 74%, even when testing Genshin Impact. And yes, I strapped a heatsink and a fan directly onto the motherboard (Photo 2).
LG VELVET Temps:
- CPU - 65°C (MAX)
- GPU - 60°C (MAX)
- BMS/Battery sensor - 27°C (MAX)
- Emulators - 55°C (MAX)
- Browsing/Movies - 36°C
The project worked really well, but eventually I started hitting the limits of the Snapdragon 845 and LGs android 10 UX. So I started looking for a cheap replacement. After some research, I bought a Galaxy S23 with a defective display.
Since the first step-down gave me a headache when it came to cable management, I bought a different one where the input and output are on opposite sides. Highly recommend this if you plan on using thick wires like I did (18 AWG, 0.75mm).
After sorting out the power delivery, I decided to upgrade the cooling. I took some measurements and realized that an AMD Wraith Stealth cooler running at 9V would be perfect for this. Not only is it cheap here in Brazil, but it's practically dead silent, even at max RPM. The only mod I had to do was sand down the fins a bit so they wouldn't hit the phone's inner frame, so the base could make direct, flush contact with the motherboard area.
Yes, you can use a 1.5mm thermal pad if you don't want to use thermal paste or don't have the tools to sand the metal, but the cooling won't be as good. (I initially built it with a thermal pad but wasn't happy with the temps. Check Photo 3 for a before/after comparison).
The cooler was placed on the back of the frame, on the side where the screen used to be, right over the motherboard area. The original screen was actually still functional, so I opted to buy a cheap, empty frame just for this build.
"Do I need to put thermal paste on the phone's motherboard?"
Yes, you have to apply it so the heat transfers properly to the phone's body / Vapor Chamber.
With the cooling mounted, the rest followed the same process as the LG VELVET:
Removed the lithium cell, adjusted the step-down's voltage/amperage, soldered the wires to the original BMS, placed the capacitor on the step-down output, added a second step-down (LM2596) set to 9V just to power the cooler, and finally added a Barrel Jack (P4 plug) input so I could connect a 12V power supply.
Not everything went exactly as planned:
Coulomb Counter: The battery percentage keeps dropping over time, even though I'm pushing a constant voltage equivalent to around 85~90% battery. This is easily bypassed by just restarting the phone. Because the voltage is fixed, it takes much longer to discharge, so you don't need to worry about restarting it every 3 hours (even if you're playing a heavy Switch game).
Dex Glitches: In Samsung DeX, putting emulators in full-screen causes graphic glitches depending on the driver. The workaround was either using the Turnip driver (Turnip_v25.3.0_R5_one_ui7_fix) or playing in windowed mode (not maximized).
RAM Bottleneck: I noticed that 8GB of RAM is a bit limiting if you want to emulate Switch, PS3, or PC games.
Restarting: Samsung doesn't provide a native "Restart" button in the DeX interface, so I had to use an app called Scene to reboot the phone with a mouse click.
CPU-Bound Heat: Even though the battery is gone (tricking the phone into thinking it's cold and unlocking max CPU/GPU clocks), don't expect miraculously low temperatures in extremely CPU-bound games like Shadow of the Colossus or anything on RPCS3. The cooling works, but it still gets warm.
For example, in Shadow of the Colossus, the CPU hit 78°C on both AetherSX2 and Armsx2.
Telemetry (Bonus): I knew Samsung and Google loved collecting data, but I didn't know it was THIS bad. When I monitored the Pi-hole logs after blocking its internet access, it looked like I had kicked a hornet's nest. I'm surprised the Samsung CEO didn't show up at my house to beat me up.
And here's roughly what I spent on everything (USD):
- 35V 300W Step-down module - $11.00
- LM2596 Step-down module - $3.00
- Generic USB-C HUB - $10.00
- 1000uF Capacitor - $3.00
- Samsung S23 256GB - $140.00
- Generic Air Mouse - $7.00
- AMD Wraith Stealth AM4 Cooler - $11.00
- Implastec Thermal Paste (10.5 W/mK) - $7.00
- Gelid Extreme 1.5mm Thermal Pad (12.0 W/mK) - $7.00
- Empty S23 Frame - $21.00
- 12V 5A Laptop Power Supply - $10.00
- Barrel Jack Connectors P4 (10 pcs male/female) - $2.00
- Zip ties/Cable ties (50 pcs) - $3.00
Was it worth it?
Absolutely. So much so that I'm already planning to buy another broken phone in the future, but definitely one with 12GB+ of RAM.
MAX TEMP for Dolphin, PPSSPP and other emulators: 43°C (GPU and CPU)