Home entertainment system grounding / static discharge issue - Page 1
Forum section: electronics / beginners

author: tobia
author_rank: Contributor
timestamp: December 08, 2020, 11:36:08 pm
content: Hi allI have a small home entertainment system comprised of the following:a fanless mini-computer with Linux, my main source of A/V data these daysa STB dish decodera blu-ray playera hi-fi amplifier, where all audio ends up unless I'm using headphonesa DLP projector, where all video ends upa number of connections between those, mainly HDMI and analog audio cablesvarious USB attachments to the mini-pc, including an El CheapoUSB-powered HDMI switchMost pieces of equipment are correctly grounded to earth, but some of them only have a groundless plug. The mini-pc in particular is powered by an isolated PSU through a +/- barrel connector, so its ground, including the ground of the stupid HDMI switch, is clearly floating.The problem is, whenever I'm sitting on my couch (synthetic fabric) and I reach for some piece of equipment, or whenever I'm wearing headphones that are connected to the PC output, I get static discharge (small shock) from my fingers to whatever chassis I'm touching, or from my ears to the metal case of the headphones.The shocks are the small ones you would expect from common static discharge, the problem is that they send a shockwave throughout the entire system and make the DLP projector lose sync on the HDMI cable for a couple seconds!I've been wondering how best to solve this issue, but I'm not sure. I would like to avoid having to wear a ESD bracelet while I'm watching the movies!Can I solve this issue by somehow connecting all the floating grounds (HDMI, USB...) to earth through a 1MΩ resistor (or better yet, one of those yellow ESD plugs)?Am I missing something really stupid about this?

author: Digorion
author_rank: Contributor
timestamp: December 10, 2020, 04:41:54 pm
content: Hello!May be antistatic spray for your couch could solve your problem? I think it costs about 3-5$.

author: Zero999
author_rank: Super Contributor
timestamp: December 10, 2020, 04:55:17 pm
content: Are you sure it's static? The fact that this only occurs with unearthed appliances, indicates it's more likely to be leakage across the Y-capacitors, in the switched mode power supplies. You probably need to connect the chasses hard down to earth, to get rid of the shock.

author: lucatz
author_rank: Contributor
timestamp: December 10, 2020, 09:03:19 pm
content: Unplug one component at a time and see which one causes issue.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: December 12, 2020, 05:57:02 am
content: Quote from: Zero999 on December 10, 2020, 04:55:17 pmApparently, we need to find out which wire the Y-capacitor is connected to and install this plug wire in the socket N of the outlet.I think the fanless PC has no a chasses...

author: Zero999
author_rank: Super Contributor
timestamp: December 13, 2020, 03:42:56 pm
content: Quote from: S. Petrukhin on December 12, 2020, 05:57:02 amReversing the plug polarity won't help, because the Y-capacitor will be connected to the bridge rectifier.

author: Digorion
author_rank: Contributor
timestamp: December 13, 2020, 04:26:30 pm
content: You can use an single-pole voltage tester (looks like a screwdriverhttps://www.haupa.com/es/productos/detalles/page/1729/product/100647/) or other types of voltage detectors to find out if the case is under high voltage.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: December 13, 2020, 08:41:53 pm
content: Quote from: Zero999 on December 13, 2020, 03:42:56 pmYes, I wrote something stupid. Sorry...