Repairing Rules / Tips to not get killed - Page 1
Forum section: electronics / repair

author: chromex
author_rank: Contributor
timestamp: January 11, 2016, 01:53:19 pm
content: Hi,This is my first post here on the forum but I've been reading threads for mostly two years and I've decided to start this new thread because i couldn't find a post dedicated to this subject.Recently i received an old Goldstar OS-7020A Oscilloscope, it has 2 Channels but channel no.1 doesn't work (the trace doesn't show up). Yes, i will start a new thread for help but first i want to make sure i wont get killed by my own mistake while repairing this oscilloscope.To begin, lets say i have a Fluke 87V and a Owon HDS1021M (two floating test equipements) for my repair.I've red and seen many post about isolation transformer and all those safety issue that i have to be aware but i think it doesnt apply to me because i basically have a battery oscilloscope. I then decided to buy one : the Tripp Lite IS250 Isolation Transformer 250W. I plan to mod it so it become a technician Isolation transformer.I would like to know the safety rules to apply when i use a battery oscilloscope and when i use a mains earth oscilloscope.Thanks for helping me hereAnd sorry for my bad english, i write mostly in french than in english

author: chromex
author_rank: Contributor
timestamp: January 11, 2016, 02:22:58 pm
content: I forgot to mention that the "Technician version" of the Isolation Transformator will be use with the DUT

author: tggzzz
author_rank: Super Contributor
timestamp: January 11, 2016, 03:31:29 pm
content: Understand the practical effects of "capacitor soakage" with high voltage capacitors. The effects on your flesh can be sudden and/or very long lasting.There are practical safety tips given in the references at:https://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/

author: Tomorokoshi
author_rank: Super Contributor
timestamp: January 11, 2016, 05:41:50 pm
content: Don't wear jewelry of any kind, including rings or watches.If I recall the story properly back in the days of large IBM mainframe computers with large linear supplies, they way they were meant to be built, anyone working on it had to remove rings and other things, because shorting it out could weld it to the terminals but not blow the fuse.Insert a Johnny Cash refrain here.I worked with a technician once who was quite rather proud of never removing his wedding ring. I had to explain the situation to him. Mine comes off as soon I get to the office or work on anything.

author: chromex
author_rank: Contributor
timestamp: January 11, 2016, 06:03:53 pm
content: What about ESD stuff? When i first opened up to see whats going on, i suprise myself having a huge amount of static on me when i was touching door handles for exemple...should i worry about it. That happens each time i work on it...

author: chromex
author_rank: Contributor
timestamp: January 11, 2016, 10:29:38 pm
content: Found this link and it pretty much answer a big part of my questionshttp://www.allaboutcircuits.com/textbook/direct-current/chpt-3/importance-electrical-safety/

author: AlphZeta
author_rank: Regular Contributor
timestamp: January 15, 2016, 06:14:25 pm
content: Be careful with the isolation transformer. Because it is an isolation transformer doesn't mean you can probe things at will, as the earth ground connections are typically shared between the input and output!

author: N2IXK
author_rank: Frequent Contributor
timestamp: January 16, 2016, 11:08:25 pm
content: Yes, the earth ground (3rd pin) is carried through. What is removed is the bond between earth ground and the neutral side of the powerline, which in the US is bonded to earth ground at the building service point. An isolation transformer provides 120V out, with both sides floating relative to earth ground.

author: helius
author_rank: Super Contributor
timestamp: January 16, 2016, 11:30:50 pm
content: Quote from: Shock on January 12, 2016, 12:30:05 amNot sure about this one, it's quite possible to cause ESD damage when a device is operating (I've done it). The 1M resistor in the strap (make sure that you don't use straps without them) will not allow dangerous currents to flow through you.