Isolation Transformer - Use One!
I'm sure it has been mentioned elsewhere, but it never hurts to remind techs to invest in an isolation transformer before they begin work on mains connected circuitry. Some variacs are isolated, some are not. But a nice isolated variac costs plenty. So does a differential scope probe. It is worth the money to invest in a 1:1 isolation transformer to prevent ugly electrical shorts between the mains and your scope, your soldering station, and other grounded test equipment.
Technically the test equipment should remain grounded through a 3 conductor plug. We've all cut that ground plug at some point for lack of a transformer, but you give up an important safety factor by doing so.
It is true that an electrical ground on all test gear can show up already existing sources of common mode noise, cause ground loops, etc. But in the end, these problems can be solved or improved without cutting the grounds. Working on the primary of a switching power supply means connecting your scope ground to one wire of the mains. Lots of computer supplies have "hot" heat sinks. Give it some thought - an isolation transformer is the right way to go.
Technically the test equipment should remain grounded through a 3 conductor plug. We've all cut that ground plug at some point for lack of a transformer, but you give up an important safety factor by doing so.
It is true that an electrical ground on all test gear can show up already existing sources of common mode noise, cause ground loops, etc. But in the end, these problems can be solved or improved without cutting the grounds. Working on the primary of a switching power supply means connecting your scope ground to one wire of the mains. Lots of computer supplies have "hot" heat sinks. Give it some thought - an isolation transformer is the right way to go.
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