ComputersTablet
Lenovo TB390FU Computer Manual
Setup, everyday use, maintenance and troubleshooting for the 12.9 in. tablet, with verified specifications.
- Memory12 GB
- Screen12.9 in.
- Est. yearly cost$1.04
About the Lenovo TB390FU
Lenovo model TB390FU is a 12.9 in. tablet that meets ENERGY STAR computer efficiency requirements.
The certified configuration includes 12 GB of memory, running Android. Retail configurations of the same model can differ, so check the system information on your unit.
Hardware listed in the certification record includes a 12.9 in. touch display (7.67 megapixels), a 39 Wh battery, and a 45 W external power adapter.
Its typical energy consumption (TEC) is 6.1 kWh per year, 70% below the ENERGY STAR limit of 20.1 kWh for its configuration. Measured idle power is 2.8 W, and sleep draws 0.2 W. The TEC figure is lower than 74% of the 104 Tablet models in our database.
Specifications
| Brand | Lenovo |
|---|---|
| Model number | TB390FU |
| Computer type | Tablet |
| Base clock speed | 3.2 GHz |
| Neural processing unit (NPU) | No |
| Memory (as certified) | 12 GB |
| Installed storage drives | 1 |
| Operating system | Android |
| Built-in display (diagonal) | 13.0 in. |
| Display resolution | 7.67 megapixels |
| Touch screen | Yes |
| Battery capacity | 39.1 Wh |
| Power adapter rating | 45 W |
| Energy Efficient Ethernet | No |
| Sleep timer (as shipped) | 1 min |
| Display-off timer (as shipped) | 1 min |
| Short-idle power | 2.8 W |
| Long-idle power | 0.2 W |
| Sleep power | 0.2 W |
| Off power | 0.2 W |
| Typical energy consumption (TEC) | 6.1 kWh/yr |
| ENERGY STAR TEC limit | 20.1 kWh/yr |
| Below ENERGY STAR limit | 70% |
Safety information
- Lithium-ion batteries can overheat if damaged. Do not puncture, crush or expose the device to high heat (for example, a closed car in summer). Stop using it and contact service if the case bulges, the battery swells or you notice a burning smell.
- Use the computer on a hard, flat surface. Do not block the vents with bedding, cushions or your lap for long periods; the underside can become hot enough to cause discomfort or burns.
- Use the 45 W power adapter supplied with the computer, or a replacement from the manufacturer with the same voltage and an equal or higher wattage rating. Inspect the cord regularly and replace it if the insulation is damaged.
- Keep liquids away from the keyboard and vents. If liquid is spilled, shut down immediately, unplug the power and let the computer dry completely before restarting.
Setup
- Unpack and inspect
Remove all packaging, protective film and cardboard inserts. Keep the box and receipt until you are sure the tablet works correctly.
- Connect power
Plug in the 45 W adapter before first start-up; the battery may ship with a low charge. You can use the tablet while it charges.
- Complete operating system setup
Follow the on-screen setup to connect to Wi-Fi and sign in with your Google account, then check Settings for system updates.
- Set up backups
Turn on cloud sync or connect an external drive and schedule automatic backups before you store important files on the computer.
Using your tablet
Sleep and power settings
As shipped, the Lenovo TB390FU turns off its display after 1 minute of inactivity and goes to sleep after 1 minute. Keeping these timers short is the easiest way to save energy. Measured sleep power is 0.2 W, compared with 2.8 W when idle with the screen on.
Battery care
The battery stores 39 Wh. At the measured idle draw of 2.8 W that is a theoretical ceiling of about 14 hours with the screen on and nothing running; real-world runtime with browsing, video or calls is shorter.
- If the manufacturer's software offers a charge limit (often 80%), enable it when the computer stays plugged in most of the time.
- Avoid leaving the computer in hot places; heat is the main cause of permanent battery capacity loss.
- For storage longer than a month, charge to about 50%, shut down fully and keep it in a cool, dry place.
- Use the operating system's battery-saver or efficiency mode when you are away from an outlet.
Performance
With 12 GB of memory, close unused apps and browser tabs to keep the system responsive.
Care and maintenance
| When | What to do |
|---|---|
| Weekly | Restart the tablet to apply pending updates and clear memory; confirm that backups completed. |
| Monthly | Install operating system and application updates. Wipe the screen and case with a soft, slightly damp microfiber cloth (power off first). |
| Every 3–6 months | Inspect the charging port and gently remove lint with a dry, soft brush or wooden toothpick; check the case and screen protector for cracks. |
| Every 6–12 months | Review free storage space and remove unused apps and large files; firmware updates arrive with the operating system updates. |
| Yearly | Check battery health in the operating system; replace the battery through an authorized service provider if capacity has dropped significantly or the case is bulging. |
Troubleshooting
Start with the simple checks below. For error messages specific to this model, use the manufacturer's built-in diagnostics and support documentation.
| Problem | Possible cause | What to try |
|---|---|---|
| Will not turn on | Depleted battery; charger not connected or faulty. | Connect the charger and wait 15–30 minutes, then hold the power button (or the restart combination in the manual) and try again. |
| Runs hot | Heavy app or game; charging in a hot place or inside a thick case. | Close demanding apps, remove the case while charging, and check the battery and app-usage screen in Settings for apps using a lot of power. |
| Slow performance | Too many background apps; storage nearly full; pending updates. | Close or disable unneeded apps, free up storage space, install updates and restart. |
| Will not wake from sleep | Software or firmware issue; accessory preventing wake. | Press the power button, connect the charger, and force-restart if needed; install the latest system update. |
| Wi-Fi drops or is slow | Weak signal; outdated software; router issue. | Move closer to the router, forget and rejoin the network, and restart the router. |
| Battery not charging | Adapter underpowered or damaged; charge limit enabled; battery worn. | Use the original 45 W adapter, check the charge-limit setting, and run the manufacturer's battery diagnostic. |
Energy use and running costs
The Lenovo TB390FU has a typical energy consumption (TEC) of 6.1 kWh per year, about $1.04 a year at $0.17 per kWh. TEC combines the measured off, sleep and idle power with ENERGY STAR's standard assumptions about how many hours a year a tablet spends in each state. It does not include time under heavy load such as gaming, rendering or video export, which can draw several times the idle figure.
| Power state | Measured power |
|---|---|
| Short idle (on, screen on, nothing running) | 2.8 W |
| Long idle (display off) | 0.2 W |
| Sleep | 0.2 W |
| Off (plugged in) | 0.2 W |
Sleep settings matter: leaving the computer on and idle for the 16 hours a day you are not using it adds about 16.4 kWh ($2.78) a year, versus 1.17 kWh ($0.20) if it sleeps during those hours.
Frequently asked questions
What processor and memory does the Lenovo TB390FU have?
The certified configuration has 12 GB of RAM. Other retail configurations may differ.
How much electricity does the Lenovo TB390FU use?
Its ENERGY STAR typical energy consumption is 6.1 kWh per year — about $1.04 at $0.17/kWh. It draws 2.8 W at idle and 0.2 W in sleep.
How big is the battery in the Lenovo TB390FU?
The battery is rated at 39 Wh, which is under the 100 Wh carry-on limit for U.S. flights without airline approval. Runtime depends on screen brightness and workload.
What size is the Lenovo TB390FU screen?
It has a 12.9 in. touch display with a resolution of about 7.67 megapixels.
What operating system does the Lenovo TB390FU run?
It was certified with Android.
Does the Lenovo TB390FU have an NPU for AI features?
The certification record does not list an installed NPU for this configuration. If on-device AI features matter to you, check the processor specifications for your exact unit.
What charger does the Lenovo TB390FU use?
It ships with a 45 W external power adapter. Replacements should match the voltage and connector and be rated for at least 45 W.
Sources and disclaimer
Specifications on this page come from the ENERGY STAR certified computers dataset published by the U.S. Environmental Protection Agency (record certified January 14, 2026), retrieved October 7, 2026.
The setup, operating, maintenance and troubleshooting guidance is written by ManualHarbor's editors for this specific product type and configuration. It is an independent guide — not a reproduction of the manufacturer's manual — and ManualHarbor is not affiliated with Lenovo. Always follow the safety instructions, installation requirements and warranty terms supplied with your unit, and contact Lenovo or an authorized service provider for warranty repairs and replacement parts.
Running-cost figures use assumed U.S. average utility prices and are estimates for comparison only. See our editorial methodology for details.
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