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 Test equipment power supplies.
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 Return to top of page · Post #: 1 · Written at 9:21:37 PM on 17 August 2017.
Dalpets's Gravatar
 Location: Adelaide, SA
 Member since 17 August 2017
 Member #: 2154
 Postcount: 10

Is it safe to test(verb)) equipment having a 110V/50Hz power supply requirement with an oscilloscope of 240V/50Hz (for alignment purposes)?

Please assume for this purpose that access is already separately available to both supply sources.


 Return to top of page · Post #: 2 · Written at 9:37:40 AM on 18 August 2017.
Sirwin's avatar
 Location: QLD
 Member since 10 April 2009
 Member #: 465
 Postcount: 106

Provided both use isolating type power transformers there will be no problem. The CRO certainly will. I'm 99% sure the other piece of equipment will too, but if it is of USA manufacture it would be worth checking. Make sure there is no continuity between the common output terminal and either of the power plug pins. I'm assuming it is some sort of service RF oscillator?


 Return to top of page · Post #: 3 · Written at 10:48:54 PM on 18 August 2017.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4749

It would be pertinent to know if the US one has a transformer? US & Europe have a nasty habit of making stuff without them & the Europeans also have a bad habit of using what looks like a transformer & is not either: Often its a tapped ballast coil.

Beware of modern test equipment & valve radios. Some DVM's will not handle RF well & can flash over internally and a lot of modern stuff cannot handle valve radio voltages. If you hook the CRO to the OP plate, the audio signal may get it.

Do not input too much signal if its got AGC? If it cuts in you will never get it right. I normally never hook up the CRO earth. I have a couple of 110V things here & use the CRO's on them. Mine will handle Plate volts.

When you get a treacherous transformerless set, dangers abound, isolation transformers (not auto transformers) get used and signal generators are never directly coupled to them.

 Return to top of page · Post #: 4 · Written at 11:35:27 PM on 18 August 2017.
Dalpets's Gravatar
 Location: Adelaide, SA
 Member since 17 August 2017
 Member #: 2154
 Postcount: 10

Initially, I will be probing a Heathkit IG-102RF signal generator for alignment, associated with an 25 MHz vintage CRO, (manufactured here in Australia).

The setup I propose using is an isolated 240v toroidal supply, followed by an 240 to 110V transformer, the latter being subject to a 300VA limitation, for this sig gen and any other equipment of nominal 110V.

I propose to use the CRO on a separate 240V source without isolation, given that it is apparently only necessary to float probed equipment.

How does this proposal sound for safety to me and the equipment?

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