hi all, i'am planning on taking waveform measurements in a plasma tv. I will be using both hot and cold grounds. the isolation trans that I have were made for tv servicing. my question is, do I use two iso trans, one for the tv and one for the scope? as I recall the scope shouldn't be isolated, only the tv. is this correct?
I challenge anyone to show me a PLasma TV schematic that does not have a transformer-isolated primary side switching regulator.
They will have 2 pin AC plugs and two different internal ground points. Only one is safe.
One AC gnd is for primary side rectifier return ( not to be connected to scope gnd) and the other one is for secondary DC out which connects to all audio video peripherals safely.
There will be a small valued 3kV+ rated coupling cap and > 1M Resistor bridging the two grounds for noise reduction.