How to Reliably Power HDMI Dongles: TV USB Ports Versus Dedicated Adapters

Your HDMI dongle keeps dropping signal. The screen goes black for two seconds in the middle of a boss fight. You are blaming the dongle. Stop. The problem is almost certainly your TV's USB port, and the fix is a five-dollar wall adapter. The choice between powering an HDMI dongle from the TV or from a dedicated adapter is the single most common failure point in retro upscaling setups. It has nothing to do with the scaler's video processing. It is a power delivery problem.

How Dongles Draw Power

An HDMI dongle like the Marseille mClassic draws its operating current from the HDMI port. The HDMI specification allows the source device to supply up to 50 mA on the +5 V line, which is 0.25 W at best. The device needs 5 V at 1 A, which is 2.5 W typical. That gap is an order of magnitude beyond what the HDMI port can deliver. The unit tries to compensate by drawing additional power from its USB input. If that USB input is connected to a TV port that cannot sustain the amperage, the voltage sags. When the voltage drops below the processor's minimum operating threshold, the unit resets. You see a signal dropout. This is not a fault of the scaler. It is a fault of the power chain.

The Same Failure Mode Across Devices

This failure mode affects any HDMI dongle that uses HDMI port power plus a USB supplement. The mClassic is the most common case because of its popularity in retro gaming circles, but the principle applies to any device that expects 5 V at 1 A from a source that cannot guarantee it. The manufacturer's Quick Start Guide explicitly states that an unpowered HDMI source is insufficient and that external USB power is required. The red LED on the unit lights up when it is underpowered. A green LED means it has enough. Check that LED before you troubleshoot anything else.

TV Ports Are Built for Flash Drives

A TV USB port is designed for media playback from a flash drive or for powering a streaming stick that draws under 0.5 A. The USB 2.0 specification allows up to 0.5 A, and USB 3.0 allows up to 0.9 A, but many TV manufacturers underspec the port to save cost and heat. A typical Hong Kong market TV from 2020 to 2024 delivers between 0.3 A and 0.5 A on its USB port, measured at 5 V. That is between 1.5 W and 2.5 W. The mClassic needs 2.5 W at peak. If your TV's USB port delivers 0.4 A, that is 2.0 W, and the unit will brown out during high-processing scenes such as context-adaptive anti-aliasing on a busy Super Nintendo screen.

Voltage sag makes it worse. Even if the port is rated for 0.5 A, the voltage at the dongle's USB input can drop below 4.75 V under load because of the cable length and the TV's internal wiring. A 0.25 V drop at 1 A is enough to push the processor into reset. The fix for power dropout is almost always the same: stop using the TV USB port.

Why a Wall Adapter Solves It

Dedicated USB mains adapters are regulated. A 5 V 1 A adapter from a reputable brand maintains its voltage within 5 percent under full load. That is a steady 5 V at 1 A, which is 5 W, double what the device needs. The margin is comfortable. The sag that plagues TV USB ports does not happen with a wall adapter because the power supply has its own regulation circuit and a direct connection to mains power. For the mClassic, a phone charger from any major brand works. For a RetroTINK 5X Pro, which requires 5 V at 1 A minimum, the same rule applies. For a RetroTINK 4K, which needs 5 V at 2 A, the TV USB port is even more hopeless.

Device	Voltage	Minimum Current	Power Connector	Adapter Included
mClassic	5 V	1 A	Micro-USB	No
OSSC v1.6	5 V	500 mA (1 A recommended)	2.1 mm x 5.5 mm barrel jack	No
RetroTINK 2X Pro	5 V	500 mA	Micro-USB	Cable only
RetroTINK 5X Pro	5 V	1 A	USB-C	Cable only
RetroTINK 4K	5 V	2 A	USB-C	Cable and 5 V 2 A USB mains adapter

Powering the mClassic

Any 5 V 1 A USB mains adapter that uses a BS 1363 plug works in Hong Kong. The power connector is Micro-USB. Use the cable that came with the unit or any standard Micro-USB cable rated for at least 1 A. Do not use a cable longer than 1.5 metres. Voltage drop over distance becomes measurable at 1 A. A cheap USB cable from a Sham Shui Po stall with thin gauge wire can lose 0.3 V over two metres, which is enough to trigger the red LED.

Powering the OSSC

For the OSSC, the power input is a 5 V DC centre-positive barrel jack with a 2.1 mm by 5.5 mm plug. The OSSC wiki recommends a 5 V 1 A regulated supply. The OSSC does not include a power supply, so you must buy one separately. A generic 5 V 1 A switching adapter with the correct plug works, but check the polarity. Centre-positive is standard for most consumer electronics. A reverse-polarity adapter can damage the OSSC. The OSSC wiki hardware specifications confirm the requirement.

Powering the RetroTINK Line

For the RetroTINK 2X Pro, power comes through Micro-USB at 5 V 500 mA minimum. The product page states that a USB-A to Micro-USB cable is included, but no mains adapter. A phone charger rated for 5 V 1 A covers it.

For the RetroTINK 5X Pro, power is USB-C at 5 V 1 A minimum. The product page includes a USB-A to USB-C cable but no adapter. Again, any 5 V 1 A phone charger works.

For the RetroTINK 4K, power is USB-C at 5 V 2 A minimum. The product page includes both a USB-C cable and a 5 V 2 A USB mains adapter. That is the only scaler in the table that ships with a proper adapter, which tells you something about the power demand.

Every Link in the Chain Matters

Power delivery stability matters most in retro gaming upscaling because the equipment is often connected in a chain: console, scaler, display, capture card. Every link adds a potential power dropout. The fix for the mClassic is straightforward, but the underlying problem of underspec ports affects every HDMI dongle that draws significant current from the bus.

The mClassic is not the only device affected. The GBS-Control board, a community-developed firmware for the GBS-8200 VGA scaler, draws power through its own barrel jack. The RetroTINK line uses USB. The OSSC uses a barrel jack. None of these devices should be powered through a TV USB port if you want stable operation. The single exception is a scaler that draws under 0.5 A and has a dedicated power regulator on board. No retro gaming scaler meets that bar.

Power Each Device Separately

If you are using an mClassic with a RetroTINK or an OSSC in the same chain, power each device from its own dedicated adapter. Do not daisy-chain USB power from one scaler to another. Do not power a scaler from a console's USB port. Console USB ports are unregulated and share power with the console's own load. The power source options listed in the Quick Start Guide include a TV USB port, a console USB port, or a USB mains adapter. The guide lists all three. Only the mains adapter is reliable.

The RetroTINK 4K is the ceiling of the market. It requires 5 V at 2 A minimum, which is 10 W. No TV USB port on the market delivers that. The RetroTINK 4K ships with a 5 V 2 A USB mains adapter. Use it. Attempting to power a RetroTINK 4K from a TV USB port will cause the device to fail to initialise or to reset during operation. The blue LED will not light, or it will flicker. The product page includes the adapter for a reason.

If you lose the adapter, any 5 V 2 A USB-C power supply that complies with USB PD or QC works. A phone charger rated for 5 V 2 A is fine. A laptop USB-C charger rated for 20 V at 3 A will negotiate down to 5 V at 2 A over USB PD, which also works. Do not use a charger that only outputs 5 V at 1 A. The RetroTINK 4K will draw more than the supply can deliver and the voltage will sag.

The most common failure is not the scaler or the dongle. It is the assumption that a TV USB port is a regulated power supply. It is not. It is a convenience feature for low-power accessories. Treating it as a power source for a 2.5 W HDMI dongle is the mistake that causes every dropout you have been seeing. Use a dedicated 5 V 1 A USB mains adapter with a short cable. The problem disappears. The LED turns green and stays green. The RetroTINK stays locked. The signal stays on screen.