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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders. |
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29th Apr 2020, 10:23 am | #1 |
Heptode
Join Date: Nov 2009
Location: Scarborough, North Yorkshire, UK.
Posts: 510
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Variac
I've just been putting an open frame type 1 amp small Variac into a metal box, with terminal on the top. Then I has another idea, why not fit a bridge rectifier and have another set for DC. After fitting the rectifier and just put the lid on and had another brain wave, why not fit a bit of smoothing. This is becoming like Ford cars, products of continual improvement. Any comments and suggestion values etc will be appreciated. Ted
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29th Apr 2020, 10:36 am | #2 |
Octode
Join Date: Jun 2013
Location: Huddersfield, West Yorkshire, UK.
Posts: 1,795
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Re: Variac
Ted. In my view any DC supply like that should have Isolation... You could be making a serious health hazard.
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Should get out more. Regards Wendy G8BZY |
29th Apr 2020, 11:36 am | #3 |
Nonode
Join Date: Jun 2016
Location: Bognor Regis, West Sussex, UK.
Posts: 2,294
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Re: Variac
I agree, you need an isolation transformer.
Peter |
29th Apr 2020, 2:05 pm | #4 |
Heptode
Join Date: Nov 2009
Location: Scarborough, North Yorkshire, UK.
Posts: 510
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Re: Variac
Many thanks, Wendy and Peter I appreciate your comments. Pleased to say I have an isolation transformer. Comes a time when space becomes a premium. Ted
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29th Apr 2020, 3:17 pm | #5 |
Octode
Join Date: Jun 2013
Location: Huddersfield, West Yorkshire, UK.
Posts: 1,795
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Re: Variac
Ok Ted... David G4EBT put me right.... I didn't realise you were part of our venerated group....should have looked on the left column.
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Should get out more. Regards Wendy G8BZY |
29th Apr 2020, 5:25 pm | #6 |
Heptode
Join Date: Jan 2008
Location: Shrewsbury, Shropshire, UK.
Posts: 838
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Re: Variac
There used to be a company that sold one of these 'Death-Traps' It was the Service Trading Company. I actually have one here.
As soon as I received it, I removed the 4 very early silicon rectifiers & returned the unit back to AC only! There was a warning label on the front panel in respect of not earthing the output We had one of these units in our workshop back in the 60's, & it was of course both useful & lethal. There were still D.C. mains in some of the areas that I worked, so one can understand how the company that manufactured this item had decided to do so. David |
29th Apr 2020, 5:27 pm | #7 |
Heptode
Join Date: Mar 2017
Location: Cedar Grove, Wisconsin, USA.
Posts: 823
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Re: Variac
I did the same thing!
I got a 5 amp Variac and a large AC 150V Simpson voltmeter mounted in a cleverly made enclosure of aluminum and wood. The output is an AC receptacle. The was enough room to include a bridge rectifier and smoothing capacitor, terminated in binding posts. Being in 120v, 60cycle land, I seldom give it a thought about isolation. I don't use the DC source that often. The next unit I build will have an isolation transformer. Maybe a little foolhardy at times, Dave USradcoll1 |
30th Apr 2020, 6:14 am | #8 |
Dekatron
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,657
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Re: Variac
Ted, if you put a voltage doubler and a limiting resistor and neon in a little box, you have an excellent HV limited DC source for testing and reforming caps, this plugs into your variac/iso tfmr.
Andy.
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