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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

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Old 15th Sep 2018, 12:18 pm   #41
Scott37
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Default Re: Can I use a shaver plug and socket ???

I also read somewhere that you should not use a shaver socket for an electric toothbrush because it is designed for intermittent use only. Any merit in this?
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Old 15th Sep 2018, 1:19 pm   #42
julie_m
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Default Re: Can I use a shaver plug and socket ???

Surely an electric toothbrush is an intermittent load?
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Old 15th Sep 2018, 2:12 pm   #43
rambo1152
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Default Re: Can I use a shaver plug and socket ???

I suppose what Scott is saying is that a traditional electric shaver is only plugged in when it is being used, but a rechargeable toothbrush is typically plugged in continuously.
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Old 15th Sep 2018, 2:24 pm   #44
julie_m
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Default Re: Can I use a shaver plug and socket ???

Ah, yes. A rechargeable toothbrush would be drawing power all the time it was not in use; but it would only be drawing a minimum amount of power, so the transformer would run cooler than it would under full load.

There would have used to have been type-approval testing for electrical appliances intended for use in the especially hazardous area of a bathroom.
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Old 15th Sep 2018, 2:44 pm   #45
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Default Re: Can I use a shaver plug and socket ???

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Originally Posted by Scott37 View Post
Sorry, Dave, if this was a digression too far but I am new to this forum! I was commenting that modern safety instructions usually cover every conceivable hazard and using the example I cited to illustrate how far this can go.
I "got" it Scott. Mind you, I once lost a perfectly good pair of speakers by playing the data segment of an old "mixed mode" CD. Perhaps I should have RTFM.
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Old 15th Sep 2018, 2:49 pm   #46
Humber888
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Default Re: Can I use a shaver plug and socket ???

I just had a look at my electric toothbrush charger where the stated power consumption is 0.4-1.4W at 100-240V. This is much lower than a typical electric shaver which could consume 15-20W when in use. Shaver transformers are designed to respond to over-current demands by rapidly dropping their output voltage to near zero as demand begins to exceed the rated output power. As a consequence their voltage regulation is much poorer than a conventional transformer and a low power draw can result in an output voltage significantly higher than the stated nominal.

I seem to remember seeing a quote that the output could be up to 270V at the nominal 240V socket at very low current draws. This is why you should be careful using a shaver socket (containing an in-built transformer) to feed an electric toothbrush charger. Better to use the 115V output if your charger voltage range will take it. The output voltage will still be higher than nominal, but nowhere near the 240V charger limit.
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Old 15th Sep 2018, 2:50 pm   #47
G6Tanuki
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Default Re: Can I use a shaver plug and socket ???

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Originally Posted by julie_m View Post
Surely an electric toothbrush is an intermittent load?
The toothbrush itself is only used intermittently, but they're generally designed to be left on charge continually (with coupling between the charger and the toothbrush itself being inductive).

The transformers in electric shaver units are generally designed to saturate easily, as a safety-feature: this provides a current-limit and a rapid drop of voltage once the current-draw reaches the design 'turnover' value.

[I once thought I could use one of these transformers - rectifying/smoothing its 115V output - as the HT supply for a piece of battery-valve equipment. Having felt how hot it got even with only 1/2 a Watt or so being drawn from the secondary, I soon changed my design plans]
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