I just owned a desktop PC and as display I connected my TV through HDMI cable.

Today I changed the HDMI cable to one that can handle 4K resolutions. So I disconnected the old HDMI cable and then with the new cable I connected first the PC side and the the TV side and I got a spark in the metal part of the HDMI plug when I was trying to connect it. Also if I touch the TV HDMI port a get a little shock in my finger.

The TV only has a 2 prong power cord, so it doesn't have the earth pin.

Does this is potentially dangerous to my PC?

I've read this in different forums but there are very spreaded ideas:

  1. It is very risky and that could fry the GPU.
  2. The earth pin is not necessary because the TV has plastic case (I know that ground is needed to avoid electric shocks to users when live wire touches the chasis but this is not the case)
  3. Coax cable can be the best way to ground a TV (if it has 2 prong plug cable)
  4. Some manuals (of TV with 2 prong plug cable) says that to connect an HDMI device everything needs to be powered off and unplugged from any source to make the connection (this makes sense so the TV will be grounded with the HDMI cable so no shocks and fried GPUs)
  5. Nothing will happen those sparks will be uncharged by the grounded device.

Any of these Ideas are true? (Especially #4)

I really don't know if is safe or not to connect all again.

Thanks in advance.


Just to give more information...

The TV and PC are connected to AVR outlets of a voltage regulator. Also a modem and a Nintendo switch dock are connected there.

The modem has a phone line that is plugged into the voltage regulator phone line protection.

The Voltage regulator has 1000W capacity. And the outlet where is connected is grounded properly.

The TV and modem are connected through Ethernet cable. Also the Nintendo Switch dock is connected through HDMI cable. Nintendo switch dock does not have earth pin.

  • \$\begingroup\$ Welcome to EE.SE! Sounds like your common Y-capacitor discharge. Are both devices grounded? Should one have ground but is connected to an ungrounded outlet? \$\endgroup\$ – winny Jul 31 at 13:22
  • \$\begingroup\$ The TV and PC are plugged in AVR outlets of a 1000W voltage regulator, and the outlet where it is plugged is grounded and TV has 2 prong plug cable so I cannot ground it. \$\endgroup\$ – Tonny Davila Jul 31 at 13:29
  • \$\begingroup\$ Is the PC grounded or ungrounded? Is it grounded via any other device? \$\endgroup\$ – Justme Jul 31 at 13:42
  • \$\begingroup\$ PC is grounded by earth pin in the power plug \$\endgroup\$ – Tonny Davila Jul 31 at 13:43
  • \$\begingroup\$ "if I touch the TV HDMI port a get a little shock in my finger." - so don't do that. \$\endgroup\$ – Bruce Abbott Aug 3 at 6:57

This is just equalization of voltage between the two isolated and ungrounded (thus floating) switchmode power supplies in your TV and PC.

It is not dangerous, since the chassis exterior of the connector will always connect first on all connectors where this could cause damage.
Unless you own non-compliant cables or somehow manage to contact the pins before chassis.

However, on some cheap equipment this discharge may cause some operational glitches.

This potential difference, usually around half of mains voltage, could be tingly for you. Especially if the leakage current of all connected power supplies adds up (eg: blu-ray + xbox + tv).
You have the GFCI to prevent hazardous circumstances on any equipment failure.

Coax is not guaranteed to be grounded, ask your service provider. Usually you have to provide earthing of the entry point yourself. If it is grounded, then yes, all devices it is connected to do have some ""ground"". But the discharge will still occur if only one of the devices is connected to ground.

There seems to be some misunderstanding in the comments about devices that do not have grounding, eg: the device has a 2-prong plug. These devices may have exposed metal for connectors, such as USB or HDMI, and these devices are not dangerous.
Standards dictate they may have some non-harmful limited leakage current, you may recognize these class of devices by double square symbol.

enter image description here

A device that does not have this symbol, but has a two-prong plug, are non-compliant and can be seen as dangerous.

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  • \$\begingroup\$ Good to know that is not dangerous for my PC .. so is not needed to ground the TV through a coax cable right? (I don't have one connected) \$\endgroup\$ – Tonny Davila Jul 31 at 13:12
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    \$\begingroup\$ It is dangerous. If for some reason the chassis has a loose connection and data pins still connect, it might damage the PC or TV. This is exactly the reason why manuals say to disconnect devices from mains and only connect them unpowered. \$\endgroup\$ – Justme Jul 31 at 13:38
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    \$\begingroup\$ HDMI is specifically engineered to be hot pluggable, therefore it is safe to do so. Your argument "but if something is broken it is dangerous" is true for a long list of things, but does not prove that HDMI is dangerous; it proves that failed equipment might be dangerous, but this is true for anything, not specifically for HDMI. \$\endgroup\$ – Vladimir Cravero Jul 31 at 15:06
  • \$\begingroup\$ Thank you all folks. I will connect everything again unplugged just for safety. \$\endgroup\$ – Tonny Davila Jul 31 at 15:40
  • \$\begingroup\$ @VladimirCravero Indeed HDMI is supposed to be hotpluggable interface. However having an interface that supports hot-plugging does not mean it can handle everything. If the devices have potential difference, due to for example one device being grounded and another floats capacitively with mains due to it's power supply or is incorrectly connected to ungrounded outlet, no interface handles that (except Ethernet which is galvanically isolated to handle more than 1000V). \$\endgroup\$ – Justme Jul 31 at 16:06

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