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ppppenguin · 24th Jan 2005, 3:07 pm

A safety warning to all of you who are tempted to try this sort of thing. Darius has a proper high voltage scope probe for making those measurements. Unless you are lucky these are rare and/or expensive. An ordinary scope probe will be rapidly fried, along with the scope's input stages. You will probably get a nice shock but may live to tell the story. A simple resistive dropper, as used for EHT voltage measurement, will be safe but stray capacitances will ensure that the waveforms you see are totally false.

The other useful device for this sort of measuremnt is a current probe. This will clip round a wire and enables you to display the current waveform on a scope. Please be careful when probing in high voltage circuits. The probe's own insulation may not be adequate when clipped round the anode lead of a line output stage.

I don't have either a current probe or a high voltage probe but I have used both types in the past.
Again. Please take care. Darius and I probably know what we are doing when mucking about with this sort of thing and we don't want to to see too many toasted TV enthusiasts.

24th Jan 2005, 3:07 pm	#3
ppppenguin Retired Dormant Member Join Date: Dec 2003 Location: North London, UK. Posts: 6,168	Re: PYE FV1 line output stage efficiency A safety warning to all of you who are tempted to try this sort of thing. Darius has a proper high voltage scope probe for making those measurements. Unless you are lucky these are rare and/or expensive. An ordinary scope probe will be rapidly fried, along with the scope's input stages. You will probably get a nice shock but may live to tell the story. A simple resistive dropper, as used for EHT voltage measurement, will be safe but stray capacitances will ensure that the waveforms you see are totally false. The other useful device for this sort of measuremnt is a current probe. This will clip round a wire and enables you to display the current waveform on a scope. Please be careful when probing in high voltage circuits. The probe's own insulation may not be adequate when clipped round the anode lead of a line output stage. I don't have either a current probe or a high voltage probe but I have used both types in the past. Again. Please take care. Darius and I probably know what we are doing when mucking about with this sort of thing and we don't want to to see too many toasted TV enthusiasts.