The USB Hub or Adapter in Your Mystery Box: What It Can Power
A USB hub or a USB-C adapter is the kind of item you plug in, watch half of it work, and decide is broken. Usually it is not; it is a hub asked to run more than one port's worth of power, or an adapter asked to carry a video signal the laptop never offered. Here is what a port gives, what a bus-powered hub can run, why the HDMI socket sometimes does nothing, and three checks.
A Port Is a Budget
Every USB port on your computer has a power budget, and you never see it until you exceed it. A USB 2.0 port is allowed to supply about 500 milliamps at 5 volts, two and a half watts. A USB 3 port is allowed about 900 milliamps, four and a half watts. A USB-C port can offer more if your laptop was built for it, but many cheap laptops and most phones give you the same few watts through it. A hub with no power supply of its own, which is what your mystery box hub almost always is, takes that one port's budget and divides it among four or seven sockets. Nothing you plug into the hub gets more than the port had to begin with, and everything you plug in shares it with everything else you plug in.
That is the whole of the "half of it works" problem you are seeing. Your keyboard, mouse, flash drive and wireless receiver together draw a few hundred milliamps and a bus-powered hub runs all of them happily. A portable hard drive on its own can want most of an amp to spin up, a phone on charge wants more, and a webcam or a ring light wants a good share; add one of those to a hub already carrying three things and something drops out, usually the last thing you plugged in. What the cables themselves can carry is in how to read the USB cables in your mystery box; a hub inherits the limits of the cable and the port behind it.
What a Bus-Powered Hub Can Run
- A hub without its own power supply divides one port's few watts among its sockets; keyboards, mice, flash drives and receivers are fine, portable hard drives and charging phones are not.
- The HDMI socket on a cheap USB-C adapter only works if the laptop's USB-C port supports video output, which many budget laptops and most phones do not; the adapter cannot add it.
- Test with the hub plugged straight into the computer, one device at a time, before you decide anything is faulty.
| Device | Typical draw | On a bus-powered hub from a laptop | What to do instead |
|---|---|---|---|
| Keyboard, mouse, wireless receiver | Under 100 mA each | Fine, several at once | Nothing |
| Flash drive, memory card reader | 100 to 300 mA | Fine, one or two | Nothing |
| Webcam, ring light | 200 to 500 mA | Marginal; may flicker with other devices | Plug it into the computer directly |
| Portable hard drive | Up to 1 A at spin-up | Often fails to mount or disconnects | Direct port, or a hub with its own power supply |
| Phone on charge | 1 to 3 A | Charges very slowly or not at all | A wall charger |
| A second hub | Shares the same budget again | Unreliable | Do not chain hubs |
| Anything with its own power adapter | Nothing from the hub | Fine | Nothing |
Read the fourth and fifth rows before you write to anyone. A hub that will not run your hard drive or charge your phone is a bus-powered hub doing exactly what its design allows, and your fix is a direct port or a hub with a power brick, which the box did not include. A hub that will not run a mouse on its own, on a direct port, is something else.
Note: The HDMI socket is the one that disappoints you most, and the reason is on your laptop, not the adapter. Video over USB-C uses a mode the laptop's port has to support, and a great many budget laptops, and almost all phones, have USB-C ports that carry data and charging but no video. Plug such an adapter in and the USB sockets work, the card reader works, and the HDMI socket shows you a black screen. Look up whether your laptop's USB-C port supports "DisplayPort Alternate Mode" or video output; if it does not, no adapter in the world will draw a picture from it.
The Three Checks
- Direct port, one device. Plug the hub into the computer itself, not a monitor or another hub, and connect a mouse alone. It should work for you at once with no driver. If it does not, try a second port and a reboot; still dead is a fault.
- Add devices one at a time. Keyboard, then a flash drive, then the receiver. Note which addition, if any, makes something drop out; that is the budget you have just found, not a fault.
- For a USB-C adapter with HDMI, confirm the laptop's port supports video before you judge the HDMI socket. If it does and the screen stays black on a known-good cable and monitor, that socket is faulty.
A hub dead on a direct port, a socket that works only when the plug is held at an angle, or an HDMI output that stays black on a laptop with a video-capable port are faults to report inside the seller's window with photographs; the routine is in how to document a mystery box on arrival. A hub that cannot spin your hard drive is a hub.
Two Things Worth Knowing About Cheap Hubs
They get warm, and that is normal up to a point. A USB-C adapter carrying video and a few devices runs warm when you touch it; one that is hot to hold, or that makes the laptop throttle, is drawing more than it should and comes out. And they identify to your computer as what they are: a hub is a hub, and the devices behind it appear as themselves. A hub that makes the computer report a keyboard when nothing is typing is the one case that ends the test, for the reason set out in is it safe to plug in a USB gadget from a mystery box. Your wireless receivers sit happily on a hub for keyboards and mice, but a receiver behind a hub behind a desk can lose range; where to put it is in wireless keyboard or mouse from a mystery box: dongle, Bluetooth, pairing.
What This Means When You Order
You should expect a hub from a mystery box to be bus-powered, good for small peripherals and not for drives or charging, and a USB-C adapter's HDMI socket to depend entirely on the laptop it meets. Ask the seller whether hubs and adapters in their boxes are tested on a computer before dispatch; Mewoo powers on devices before packing and states what its boxes are built around, and any seller should tell you the same. Then plug it into a direct port with one device, add the rest one at a time, and keep the hard drive on the laptop's own socket.
FAQ
Why does my USB hub only work with some devices?
Because it has no power of its own and is sharing a single port's small allowance across every socket. Low-draw items such as a mouse, a keyboard, a flash drive or a receiver fit inside that allowance together; a hard drive spinning up, a phone charging or a webcam with a light can each want most of it, and once the total is exceeded the last device added drops out. Move the hungry device to the computer's own port.
What is the difference between a powered and an unpowered hub?
A powered hub has its own wall adapter and gives each socket a proper supply, so it can run hard drives, charge phones and feed several cameras at once. An unpowered, or bus-powered, hub borrows the few watts from the port it plugs into and shares them out, which suits small peripherals only. Boxes ship the unpowered kind almost without exception, so treat it as an extension for mice and keyboards rather than a docking station.
The HDMI port on my USB-C adapter shows nothing. Is it broken?
Check the laptop before the adapter. Sending video through a USB-C port needs a capability the port itself must have, and many budget laptops and nearly every phone lack it, even though data and charging through the same port work fine. Search your laptop model for "USB-C video output" or "DisplayPort Alt Mode". Where the port is capable and a good cable and monitor still give a black screen, blame the adapter; where it is not, nothing can help.
Can I charge my phone through the hub?
Slowly at best. A bus-powered hub can pass only a fraction of an amp to a phone, and with anything else plugged in the phone gets less still, so you will see a trickle or a "not charging" message. That is not a defect. Use a wall charger for the phone and keep the hub's sockets for devices that need data. A pass-through charging port on a USB-C adapter is for the laptop's own charger, not the phone.
Is it safe to plug an unknown USB hub into my computer?
As safe as any USB accessory, with the same one-second check: watch the screen when you connect it. Every device you plug into it ought to show up under its own name and nothing else. If the computer announces a keyboard nobody attached, or text begins to type itself, unplug it and stop. Beyond that, a hub carries no storage and cannot hide files, and the ordinary cautions about drives do not apply to it.
Why does the hub get warm?
Because the small chip inside converts and routes power and data for every socket, and a USB-C adapter carrying a video signal works harder still. Warm to the touch is expected. Hot to hold, a smell of plastic, or a laptop that slows down while the adapter is connected means the adapter is drawing too much or is poorly made, and it should come out. Give it air rather than burying it behind the laptop against a wall.
Final Thoughts
A hub from a mystery box shares one port's few watts among its sockets, so it runs keyboards, mice, drives and receivers and fails on hard drives and phones; that is the design, not a fault. A USB-C adapter's HDMI socket works only on a laptop whose port carries video. Test on a direct port with one device, add the rest one at a time, and report a hub that is dead alone.
If you want a box whose accessories are checked before dispatch, with the categories stated on the product page, start with the Triple Reveal Electronics Mystery Box (3 items) or the Party Electronics Mystery Box (6 items). Compare every tier side by side on the electronics mystery box category page.
See how devices are tested before dispatch →
