Tweakers' Asylum

using 120v on a 240v piece of equipment

218.186.11.4

chris e.

This may be a really dumb question (and sorry in advance), but I know that one can't plug in a 110 or 120v piece of equipment into 240v outlets without disaster ensuing.

However, what if you do the opposite? I'm in Singapore (240v) and moving back to the USA (120v). I know (thanks to someone from this forum!!) that changing the voltage means higher current and so I need to change the fuse amperage in the stereo item.

But if I have a surround processor (Rotel 1066) that is set for 240v and I plug it into a 120v outlet (and assuming I upped my fuse accordingly), would there be a problem? I ask this because inside the Rotel there doesn't seem to be any easy way to convert the voltage like there is for my other equipment (Musical Fidelity Trivista SACD, Avantgarde Solos).

Is this insanity?

Thanks in advance!

Follow Ups:

RE: using 120v on a 240v piece of equipment - BT 01:15:26 05/20/07 (2)
Chris

You will need to buy a step-up transformer that converts the incoming mains voltage from 120V to 240V.

Your equipment internal circuitry runs at a much lower voltage (typically 25V - 50V) and the mains incoming transformer steps it down to the requisite internal operating voltage based on the relevant ratio.

Accordingly, 240V mains rated equipment plugged into a 120V line will be feeding only half the required voltage to the internal circuitry and accordingly, your equipment won't work.

As for current rating, you are correct in that your equipment fuse will need to be upgraded to a higher current rating based on the lower mains voltage.

Irrespective of the mains incoming voltage, the power requirement of your equipment will remain constant. Power (P) = V (voltage) X I (current). So, a piece of equipment requiring 240W will be drawing 1A on a 240V line and 2A on a 120V.

Hope this helps.
- RE: using 120v on a 240v piece of equipment - chris e. 01:56:44 05/20/07 (1)
  Thanks -- I figured it wouldn't be so easy. I'd rather not have to use a step-up but it looks like this is needed unless I can find someone who can change the transformer itself I guess.
  - RE: using 120v on a 240v piece of equipment - kellymon 07:01:38 05/20/07 (0)
    If you are using a step up transformer, you do not need to increase the fuse size in your audio equipment. You will already be at the design voltage.
    
    Be sure to get a unit large enough to handle your equipment, probably 2500-3000 watts. Most USA receptacle circuits are 20A @ 120v and a 3000 w unit will be comfortably underloaded and cruising at that load.
    Get a good one and you'll probably benefit from the electrical isolation also.
    robert

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