1. Introduction
This manual provides detailed instructions for setting up, operating, maintaining, and troubleshooting your surmen M75 75% Wireless Mechanical Gaming Keyboard. The M75 keyboard features a compact 75% layout, triple-mode connectivity (wired USB-C, Bluetooth 5.0, and 2.4GHz wireless), a gasket-mounted design with sound-absorbing pads for enhanced acoustics, pre-lubed switches, and hot-swappable sockets.

Figure 1: surmen M75 75% Wireless Mechanical Gaming Keyboard (Starlight White)
2. Package Contents
Before you begin, please ensure all items are present in the package:
- surmen M75 Keyboard
- USB-A to C Cable
- 2.4Ghz Wireless Receiver (often stored in the keyboard's back compartment)
- Keycap Puller
- Switch Puller
- Extra Keycaps (color may vary by model)
- Extra Switches
- User Manual (this document)
3. Setup and Connectivity
The surmen M75 keyboard supports three connection modes: Wired, 2.4GHz Wireless, and Bluetooth 5.0.
3.1. Wired Connection (USB-C)
- Locate the USB-C port on the back of the keyboard.
- Connect the provided USB-A to C cable to the keyboard and your computer's USB port.
- Ensure the mode switch on the back of the keyboard is set to "Line" (wired mode).
- The keyboard will be automatically recognized by your computer.

Figure 2: Connectivity Switches and USB-C Port
3.2. 2.4GHz Wireless Connection
- Locate the 2.4GHz wireless receiver, usually found in a small compartment on the back of the keyboard.
- Plug the 2.4GHz receiver into an available USB-A port on your computer.
- Set the mode switch on the back of the keyboard to "2.4G".
- The keyboard should connect automatically. If not, press Fn + R to initiate pairing.
3.3. Bluetooth 5.0 Connection
The keyboard can connect to up to three Bluetooth devices.
- Set the mode switch on the back of the keyboard to "BT".
- Press and hold Fn + Q, Fn + W, or Fn + E for 3-5 seconds until the corresponding key's backlight flashes rapidly. This indicates pairing mode.
- On your device (computer, tablet, smartphone), search for Bluetooth devices and select "surmen M75".
- Once paired, the backlight will stop flashing.
- To switch between paired Bluetooth devices, simply press Fn + Q, Fn + W, or Fn + E.

Figure 3: Triple Mode Connection Overview
Video 1: Demonstrating the M75 Wireless Gasket Mounted Keyboard's USB, Bluetooth 5.0, and 2.4Ghz connectivity options.
3.4. Operating System Switch
The keyboard has a dedicated switch on the back to toggle between Windows and Mac OS compatibility. Ensure this switch is set correctly for your operating system to ensure proper function key mapping.
4. Operating Instructions
4.1. Function Keys (Fn Combinations)
The M75 keyboard utilizes the Fn key for various multimedia and system controls.
| Function | Windows/General | Mac OS |
|---|---|---|
| Decrease Screen Brightness | Fn + F1 | Fn + F1 |
| Increase Screen Brightness | Fn + F2 | Fn + F2 |
| Calculator | Fn + F3 | Ctrl + ↑ (Mission Control) |
| Computer | Fn + F4 | Activate Siri |
| Media Player | Fn + F5 | Show all windows of the foremost App |
| Previous Track | Fn + F6 | Previous Track |
| Next Track | Fn + F7 | Next Track |
| Play/Pause | Fn + F8 | Play/Pause |
| Stop | Fn + F9 | Fn + F9 (No specific Mac function listed) |
| Mute | Fn + F10 | Mute |
| Decrease Volume | Fn + F11 | Decrease Volume |
| Increase Volume | Fn + F12 | Increase Volume |
| Lock WIN Key | Fn + WIN | N/A (Win/Alt will interchange when switching interfaces; do not lock Win) |
| Smart Key Switching | Press END key for >5s to switch to INS key. Press INS key for >5s to revert. | N/A |

Figure 4: Multimedia Key Functions
4.2. Volume Knob Control
The multi-functional knob located on the top right of the keyboard controls both volume and RGB lighting.
- Rotate Knob: Adjusts volume (default mode) or RGB brightness/speed.
- Press Knob: Mutes/unmutes audio (default mode) or switches RGB lighting modes.
- Press and Hold Knob (3 seconds): Toggles between Volume Control mode and RGB Control mode.

Figure 5: Driver Macro Customization Interface
4.3. RGB Lighting Control
The keyboard features customizable RGB backlighting with 16 unique effects and over 16.8 million colors.
- Use the volume knob (in RGB control mode) to cycle through lighting effects and adjust brightness/speed.
- The side RGB light strip can be controlled separately. The product page indicates Fn + Right Ctrl (not Right Alt as sometimes stated) to switch side light modes.
- Advanced customization, including macro programming and specific color settings, can be done via the dedicated software. (Refer to Section 4.4)

Figure 6: Side RGB Lighting
4.4. Pro Software Support
The surmen M75 supports professional software for advanced customization. This software allows you to:
- Configure macros with different keybindings or shortcuts.
- Customize RGB lighting with over 16.8 million colors and various effects.
- Record and edit macros.
- Set custom shortcut keys.
Please note: The software typically requires the keyboard to be in wired mode for proper functionality. Refer to the manufacturer's website or included documentation for software download and installation instructions.

Figure 7: Software Interface for Macro and Lighting Customization
5. Maintenance
5.1. Cleaning Your Keyboard
Regular cleaning helps maintain the keyboard's performance and appearance.
- Disconnect the keyboard from all power sources before cleaning.
- Use a soft brush or compressed air to remove dust and debris from between the keycaps.
- For stubborn dirt, gently remove keycaps using the provided keycap puller and clean the switch area.
- Wipe the keycaps and keyboard surface with a slightly damp, lint-free cloth. Avoid excessive moisture.
5.2. Hot-Swapping Switches
The surmen M75 keyboard features hot-swappable sockets, allowing you to change mechanical switches without soldering. It is compatible with most 3-pin and 5-pin mechanical switches.
- Using the provided keycap puller, carefully remove the desired keycap.
- Insert the switch puller's prongs under the top and bottom clips of the switch.
- Gently squeeze the clips and pull the switch straight up to remove it.
- Align the pins of the new switch with the holes on the PCB. Ensure the pins are straight to avoid bending.
- Press the new switch firmly into the socket until it clicks into place.
- Replace the keycap.

Figure 8: South-Facing RGB LEDs and Hot-Swappable Sockets
Video 2: Demonstration of hot-swappable switches and south-facing LEDs on the M75 keyboard.
5.3. Battery Management
The keyboard is equipped with a 5000mAh battery.
- To check the battery level in wireless mode, press Fn + Alt. The keyboard's backlights will indicate the charge level.
- Connect the USB-C cable to charge the keyboard. The ESC key's LED may turn red while charging.
- Battery life: Up to 178 hours with lights off, up to 42 hours with lights on (Bluetooth mode).

Figure 9: Battery Level Indicator
6. Troubleshooting
If you encounter issues with your surmen M75 keyboard, please refer to the following common solutions:
- Keyboard not responding:
- Ensure the keyboard is charged.
- Check the connection mode switch (Line, 2.4G, BT) is set correctly.
- For wired mode, try a different USB port or cable.
- For 2.4GHz, ensure the receiver is properly plugged in and try re-pairing (Fn + R).
- For Bluetooth, ensure the keyboard is in pairing mode (Fn + Q/W/E hold) and your device's Bluetooth is on. Try forgetting the device and re-pairing.
- RGB lighting not working or stuck:
- Ensure the keyboard is powered on.
- Check the volume knob's mode (Volume vs. RGB control) by pressing and holding it.
- Try cycling through RGB modes using the knob or software.
- If using software, ensure the keyboard is connected via wired mode.
- Keys not registering or double-typing:
- This could indicate a faulty switch. Try hot-swapping the problematic switch with one of the spare switches provided.
- Ensure the switch is fully seated in the socket.
- Software not detecting keyboard:
- Ensure the keyboard is connected via USB-C cable and the mode switch is set to "Line".
- Restart the software and/or your computer.
7. Specifications
| Feature | Detail |
|---|---|
| Brand | surmen |
| Model Number | M75 |
| Connectivity Technology | USB-C (Wired), Bluetooth 5.0, 2.4GHz Wireless |
| Keyboard Description | Mechanical |
| Layout | 75% (82 Keys) |
| Switches | Pre-lubed Linear Switches (Hot-Swappable 3-pin/5-pin) |
| Keycaps | Double Shot PBT Keycaps, Cherry Profile |
| Mounting Style | Gasket Mounted |
| Sound Dampening | 5-layer Padding (Silicone pad, sound-absorbing sponge, etc.) |
| Backlighting | RGB (South-facing LEDs, 16 effects, 16.8M colors, Music Rhythm) |
| Battery Capacity | 5000mAh Lithium Polymer |
| Battery Life (Approx.) | 178 hours (lights off), 42 hours (lights on) in BT mode |
| Compatible Devices | Laptop, PC |
| Operating System | Windows, Mac OS |
| Item Weight | 2.64 pounds |
| Package Dimensions | 14.02 x 7.2 x 2.01 inches |
| Manufacturer | GTSP |
| Special Features | Volume Roller, Backlit, Programmable Keys, Hot-Swappable |

Figure 10: Gasket Mount and 5-Layer Padding Structure
Video 3: Overview of the SURMEN M75 Gasket Mounted Keyboard with 5-layer Padding.
8. Warranty and Support
For warranty information, technical support, or further assistance, please contact surmen customer service or visit their official website. Keep your purchase receipt as proof of purchase.
- Manufacturer: GTSP
- Amazon Store: Visit the surmen Store





