Your Computer Case Gives You a Shock: Where the Voltage Comes From and Why It's Dangerous

Many people notice a strange sensation: run your hand over the metal casing of a laptop on charge and you feel a faint "vibration" or tingle. Touch the computer case and a radiator at the same time and you get a small shock. A spark jumps when you plug a cable into a monitor or TV. Most people put it down to "static" and forget about it. But in most cases it isn't static electricity at all — it's an earthing problem or a fault that harms equipment and can be dangerous.

Where the voltage on the case comes from

Every computer power supply, and most laptop chargers, contains a mains filter that suppresses electrical interference. It's designed to divert part of that interference to the device's casing and from there, through the third, earth pin on the plug, to ground. If there's no earth connection, that path is broken and a small voltage appears on the casing — roughly half the mains voltage, but at a very low current. That's what you feel as a tingle.

In Tbilisi's older buildings, and in plenty of new ones too, wall sockets often have earth contacts for show only: no wire is actually connected to them. It's a common situation, which is why complaints about computers that "bite" are so frequent.

When it's relatively harmless and when it's dangerous

A slight tingle from a healthy power supply with no earth connection is generally not life-threatening: the filter's leakage current is very small. But "relatively harmless" doesn't mean "normal". It's a very different matter if the shock is noticeable, if you feel it when touching the computer and a heating pipe at the same time, or if the tingling has appeared suddenly. That can mean an insulation breakdown in the power supply, a damaged cable or faulty wiring — in which case the full mains voltage could be present on the casing.

How it damages equipment

• burnt-out ports — when a cable connects two devices at different potentials, current flows through the port and kills USB, HDMI, network and audio sockets;
• interference and crackling in headphones and speakers, and lines on the monitor;
• network problems — dropped connections, devices disappearing, transmission errors;
• freezes and restarts when you touch the case or plug in a peripheral;
• damage to sensitive electronics — audio interfaces, printers, cameras.

Computer-to-TV and laptop-to-projector connections suffer most often: if one device is earthed and the other isn't, plugging in HDMI while both are on can burn out the port on one of them.

The main causes

No earth in the wall socket

The most common cause. The socket looks correct, but no earth wire is connected to it, or the building has no earthing system at all.

Two-pin plugs or adapters

Extension leads and adapters without an earth contact, and cheap plastic multi-plugs, break the protection completely even if the wall socket is earthed.

A faulty power supply

Insulation breakdown, swollen filter capacitors or damage from a power surge. In this case leakage can be noticeably stronger than usual.

A non-original laptop charger

Cheap adapters often skimp on insulation and filtering, and the laptop's metal casing starts to "nip" when touched.

Wiring problems

Swapped live and neutral, poor connections or a "floating" neutral in the distribution board affect every appliance in the flat or office.

Why you shouldn't fix it yourself

You'll find advice online to "earth" a computer to a radiator or water pipe. That's dangerous: if there's a fault in the building, the pipes can become live, putting neighbours and plumbers at risk of a shock. Earthing must only be done through a properly installed earthing system and checked wiring. Opening a power supply is also off-limits: the capacitors inside hold a charge even after the unit is unplugged.

How we solve the problem

1. Equipment diagnostics. A technician checks the power supply, chargers and cables for leakage and damage.
2. Checking sockets and extension leads. We measure whether earth is present and whether live and neutral are wired correctly.
3. Electrical work. Our electricians bring earth to the sockets, correct wiring faults and fit residual-current devices (RCDs) where needed.
4. Replacing faulty equipment — power supplies, chargers and unearthed extension leads.
5. Protecting your equipment — choosing surge protectors and UPS units and connecting them correctly.

Our advantage is that computer technicians and electricians work in the same team. You don't have to figure out whether the "computer" or the "wiring" is to blame — we check both in a single visit.

Call a specialist

If a computer, laptop or monitor gives you a shock, it needs checking — especially if there are children in the home. We'll come to any district of Tbilisi and the suburbs, find the cause and fix it safely. Find out more on our electrical services and computer diagnostics pages.