HP Omen Case Obelisk Panel Release & 40L Differences

The HP Omen 40L desktop’s side panel is released by removing two captive thumbscrews at the rear edge, then pulling the panel straight back and outward; the earlier Obelisk model uses a similar but slightly different mechanism. This article explains both release methods, the key differences between the Obelisk and 40L cases, and what to watch for when upgrading or servicing either.

Background: The Obelisk and 40L Generations

HP’s Omen desktop line has gone through several case designs. The Omen Obelisk (often called the 875-xxxx series) was sold roughly from 2018 to 2020. It has a minimalist, angular front with a single tempered-glass side panel. The Omen 40L (model 40L GT21-xxxx) arrived in 2021 and is the current mainstream Omen tower. It features a more aggressive front grille, a glass side panel on a hinge, and improved airflow. Both cases share the same basic layout—front intake, rear exhaust, top-mounted PSU—but the details of panel removal and internal layout differ enough that you should not assume parts are interchangeable.

How to Release the Side Panel on the Obelisk

The Obelisk’s side panel is held by two thumbscrews at the rear edge, near the top and bottom. To remove it:

1. Unplug the power cable and any external connections.
2. Lay the case on a soft surface with the glass side facing up.
3. Loosen the two thumbscrews by turning them counterclockwise. They are captive, so they stay in the panel.
4. Grasp the panel by its rear edge and pull it straight back (away from the front of the case) about 1–2 cm, then lift it off.

There is no latch or push-button. If the panel feels stuck, check that both screws are fully loose—they sometimes catch on the screw threads. Do not pry with a screwdriver; you could crack the glass.

How to Release the Side Panel on the 40L

The 40L uses a different mechanism: the glass panel is hinged at the front and secured at the rear with a single captive thumbscrew. To open it:

1. Shut down the PC and unplug it.
2. Lay the case on its side, glass up, or stand it upright if you prefer.
3. Loosen the one thumbscrew at the rear edge of the glass panel.
4. Pull the panel’s rear edge outward and swing it open like a door. It stays attached to the case via the hinge.

To fully remove the panel (for cleaning or replacement), lift it upward after opening it past 90 degrees—the hinge pins are designed to release. Some users find it easier to remove the front bezel first, but that is not necessary for basic access.

Key Differences Between the Obelisk and 40L Cases

Beyond the panel release, the two cases differ in several ways that matter for upgrades and maintenance:

• Side panel: Obelisk has a full glass panel that must be lifted off; 40L has a hinged glass door.
• Front I/O: Obelisk has two USB 3.0 ports and a headphone/mic jack on the top front; 40L adds a USB-C port and moves the jacks to the top edge.
• Airflow: The 40L has a larger front mesh intake and a 120mm rear fan; the Obelisk has a smaller front intake and often a single 120mm exhaust.
• PSU location: Both are top-mounted, but the 40L’s PSU is shorter to allow a taller CPU cooler.
• Expansion slots: Both have 7 PCIe slots, but the 40L has a vertical GPU mount option (not pre-installed on all models).
• Drive bays: Obelisk has two 3.5″ bays and two 2.5″ bays; 40L has one 3.5″ and two 2.5″ bays (plus M.2 slots).

These differences mean that some parts—like the front panel cable, the side panel itself, and the internal drive cage—are not interchangeable between the two models.

Common Problems and Mistakes

Users often encounter a few issues when removing or reinstalling these panels:

• Stripped thumbscrews: Over-tightening can round out the screw head. Use a screwdriver with the correct size (usually Phillips #2) and apply gentle pressure.
• Glass panel not seating: On the 40L, the hinge can misalign if the panel is not fully opened before lifting. Always open past 90° before removing.
• Forgetting to unplug: Always disconnect power before touching internal components. The PSU’s standby voltage can still be live even when the PC is off.
• Static damage: Touch a metal part of the case (like the PSU) before handling components, or use an anti-static wrist strap.

If a screw is stripped, you can carefully use a rubber band between the screwdriver and the screw head for extra grip, but replacement thumbscrews are available from HP or generic PC parts suppliers.

How to Choose Between the Two (If Buying Used)

If you are looking at a used Omen, the choice depends on your needs:

• The Obelisk is cheaper and has more 3.5″ drive bays, making it better for bulk storage.
• The 40L has better airflow, a USB-C port, and a more modern design. It also supports taller CPU coolers (up to about 165mm) and longer GPUs (up to 320mm).
• If you plan to upgrade the GPU, check the length limit: the Obelisk fits up to about 300mm, while the 40L fits 320mm.
• For CPU cooling, the 40L’s top-mounted PSU leaves more room for a large air cooler or a 240mm AIO in the front.

Neither case has a tempered-glass front, so RGB fans in the front are not visible—something to consider if aesthetics matter.

Costs and Availability of Replacement Parts

Replacement side panels are not commonly sold as aftermarket items. You may find them on eBay or from HP’s parts store, but prices vary widely. A used Obelisk side panel might cost $30–$50, while a 40L panel could be $40–$70. If you need a new front I/O board or cable, those are also available but may require some disassembly to replace. In most cases, you are better off buying a whole used case for parts if you need multiple components.

For the 40L, the hinge mechanism is a known weak point—if it breaks, the panel will not stay closed. You can sometimes find replacement hinges as separate parts, but they are not universal. If you are handy, a simple magnetic latch can be a temporary fix.

Safety and Handling Tips

When working with these cases, keep these points in mind:

• Always place the case on a stable, non-slip surface. Tempered glass can shatter if the panel is dropped or struck.
• Do not touch the glass with metal tools; a single hard tap can cause it to explode.
• If you are removing the panel to clean dust, use a can of compressed air or a soft brush—avoid vacuum cleaners that can create static.
• When reinstalling the panel, tighten screws until they are snug, not tight. Over-tightening can strip the threads in the case frame.

If you ever need to ship the computer, remove the glass panel and wrap it separately in bubble wrap to avoid breakage.

Frequently Asked Questions

Is the side panel on the 40L really hinged? Yes, the 40L’s glass panel is attached with a hinge at the front edge. You loosen one screw at the rear and swing it open. It cannot be removed without lifting it off the hinge pins.

Can I use an Obelisk side panel on a 40L? No. The mounting holes and hinge location are different. The Obelisk panel has two screw holes at the rear, while the 40L has one screw and a hinge. They are not compatible.

Why won’t my Obelisk side panel come off? The most common reason is that one of the two thumbscrews is not fully loosened. They are captive, so they may need a few extra turns. If the panel still won’t budge, check for a hidden screw near the front edge—some early models had one.

Does the 40L have a tool-less panel? No, it requires a screwdriver for the single thumbscrew, but the hinge means you don’t have to lift the panel off completely for routine access. Some users replace the thumbscrew with a tool-less latch, but that is a modification.

Can I remove the front bezel on the 40L to clean the fans? Yes. The front bezel is held by clips at the bottom edge. Gently pull the bottom outward, then lift up. This gives you access to the front fans and filters. The Obelisk’s front bezel is similar but has two screws at the bottom.

Are the internal components (motherboard, PSU) the same between the two? No. The 40L uses a custom motherboard with a different shape and mounting points than the Obelisk. The PSU is also different in size and wattage. You cannot swap these between models.

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