Exploring a dead shaver socket

A strategically sized PTC thermistor added internally would have self reset after an overload.

Big Clive

My friend Martin owns a Bed and Breakfast. He was regularly swapping those units out until I suggested putting a 1 amp 250v fuse in the mains wiring. (Done properly by an electrician) Cheaper to change a fuse than the units.

Nuts 'n' Proud

power-factor = watts / Volt-Amps (VA) (see https://en.wikipedia.org/wiki/Power_factor)

The blown thermal fuse in a Danish 12V 20VA old-style wallwart from the nineties I‘ve been looking at had the specs printed on it: 115degC, 1,5A, not sure if particularly fast or slow. As in the video, it was connected to the primary winding. I don’t know whether this is typical and whether I could just replace it with a resetting fuse instead. To be safe I’m replacing it with one of the same specs.

Andreas Schuderer

I can see a small (== lossy) transformer cooking itself to death on iron losses due to high supply voltage.

Mike Page

Scandi question: how common is IT earthing there? TIA - Mike.

Mike Page

I've installed them for toothbrush charger in bathroom.

Have seen them in hotels in Australia but not homes

Simon Deards VK3FSPD

Yeah, just one shot. Not a great design.

Big Clive

You could also get these (user supplied) "franzus" ones that had a tiny little WW transformer as well as a leading edge dimmer triac thing for the hairdryer and a switch to go between modes. Common at charity shops for many years, and the transformer part was always cooked.

Anton

They were common in NZ in homes, and I have seen them at times in Australia but they seem uncommon.

Anton

I have seen those quite a few times in my travels. Never worked very well with my plug in razors/trimmers without adjusting. I think that came down to 50 vs 60hertz a lot of them were old so the contacts were sketchy and the transformers always seemed to be worn out or loose and buzzed almost as loudly as my razor.

Lostngone

I am confused. So was that really a one and done thing or was it supposed to reset after cool down and just failed? Seems like they would be replacing a lot of those with hair driers, curling irons, etc.

Lostngone

Had them in Canada when I was a kid. I thought they limited current rather than isolating from ground, but I'll defer to you. I think GFCIs have been code for years and replaced them?

Peter Laws

I don't like the idea of a fuse you can't replace. Especially when using a hair dryer will kill it.

Mark Trombley

Yeah, getting a 230V shock to ground isn't fun in a wet environment like a bathroom

Stuart

I didn't even know they use isolation transformers for shaving in UK. What a complication. Learn how to shave and don't use a shaver if you're so afraid to get shocked.

I've got one here. Actually, my second. The first committed suicide within months of install, I don't recall exactly why (but it wasn't via overload). PS - Your modifications to the writing on the front almost disappear at some filming angles.

Mark Gray

Yes it does.

Big Clive

A 12V wall socket?

Big Clive

They could potentially be useful as an isolated 115/230V bench testing supply for low loads.

Big Clive

I'll never understand the british safety principles. They have no problems mounting an electric wather heater in my shower (where it's guaranteed to get wet) but they're afraid of electric sockets in the bathroom (because they could get wet). In Germany it's the other way round.

Does that word you've written on to say Forked?

Ymir the Frost Giant

We don't need shaver plugs in Europe, our shavers are petrol powered :-D

Zeedijk Mike

We had one in our bathroom, which was built into the strip light. When shopping for a replacement lit mirror cabinet, I noticed most no longer have shaver sockets. We use cordless shavers and toothbrushes, so didn't mind losing the shaver sockets, although upon assembling it, the light clearly uses non replaceable LEDs.

Seán Byrne

Most devices hobbyists work on are low voltage, and don't need an isolation transformer at all. A lot of mains powered devices can draw more than 20W, which is all these little units can handle (Clive corrected his initial guess at the capacity in his YouTube description). That thermal fuse would be in constant peril...

Never seen one in Europe. incidentally, why would an electronics hobbyist in the UK buy an expensive isolation transformer (or an 110V step down convertor for that matter) when this does exactly the same? Most devices hobbyists work on these days don't come even close to 100W...

Erwin Bierhof

Toothbrush chargers only use a watt or two at maximum, and typically less than half a watt once the toothbrush is charged. There is no way this would ever overheat a 20VA transformer, or even warm it much above ambient temperature. Vendors pushing special "electric toothbrush compatible" sockets are selling you alarmist snake oil.

Hi Clive, Would you be interested in a 12V DC version (probably broken) to dismantle?

Steve Askey

Am I right in thinking that this, even if only 20VA, would be a nice addition to any tinkerers bench next to measuring equipment so that it's a quick solution to have either DUT or scope separated from mains ?

lImbus924

I don't think it was necessarily a high power load, just a long lived one. These things are built cheap and in the enclosure have zero cooling. That's fine for 5 minutes of shaving but not for 24 hours of charging a shaver or toothbrush which slow roasts the transformer. The better ones have a shaver AND toothbrush symbol on to show they have been designed for continuous load and, frankly, should be the only type fitted in this day and age. Of course they cost more and most people prefer to save a tenner and have a thermally risky device embedded in the wall of the house... People are strange.

Charleso

I made a comment on the YT, but, probably more use here. I see these in Australia on Trains (some intercity trains in Victoria have them in the bathrooms), and I've seen them in train station lavatories, and in airports. I've never seen one in a house. I don't use hotel rooms very often, but, I have seen them in one, but in smaller more rural hotels, I don't recall seeing them.

Loscha

'merican: I don't see this in houses. They do show up in hotels. Houses have GFI (RCD) outlets with the test and reset buttons near the sink.

Nani Isobel

'merican here too. Also see them in hotels a lot, but not in houses. Only 110V-ish.

Nani Isobel

Nowday’s not very common in homes in the Netherlands. Back in the days they were mandatory. Why didn’t they put reset-able thermal fuses in these devices?

Mike Weijmans

Swede here. We used to have a 115V variant in bathrooms everywhere. In homes, in public toilets like in shopping malls, hotels and so on. We weren’t allowed to have 230V in bathrooms until we got RCD’s. Sweden got RCD’s quite late I think. It was in the 90’s when I started out as an electrician that RCD’s were becoming mandatory in newly built homes. One problem with the 115V outlets was that if they weren’t connected to the bathroom light switch and were on all the time they could run quite hot.

American here: never in anyone's home, occasionally in pricey hotels.

Russell Levine

I'm in New Zealand and have a similar socket in my bathroom with three pin-holes -- one centre hole that is shared between the 115V and 240V outlets. I've never opened it up to see if its innards are the same as this one though. A quick search and this is what it is: https://www.pdl.co.nz/products/detail?CatNo=PDL675&itemno=PDL675WH

LifeSizeTeddyBear