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  #1  
Old 22nd February 2018, 10:53 PM
Bonky Bonky is offline
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Default A naive, possible, safety idea

...well...

I believe I'm soon to make my first WD KEL84 kit...but the testing of said device with such high voltages sends a shiver down my spine.

So, has anyone thought of being able to wire a bench power supply to the PCB end of the PS at a much lower voltage (say 36V) and test from there (no valve attached obviously)?

Thanks.
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  #2  
Old 23rd February 2018, 08:10 AM
bob orbell bob orbell is offline
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Default Re: A naive, possible, safety idea

A variac is what I and many others use, with this tool you can bring the mains voltage up slowly, however, provided you exercise caution at all time's when testing high voltages, you should not have a problem, if you choose a WD kit, the instructions will take you through the whole process, a lower voltage will not tell you if all is well, you need to see that you have the correct readings that the instructions say, don't be scared, be bloody careful. BOB
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  #3  
Old 23rd February 2018, 10:11 AM
Bonky Bonky is offline
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Default Re: A naive, possible, safety idea

Thanks again Bob. Understood.

...and apologies for the clumsy title thread. I tried to edit it but couldn't.
R
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  #4  
Old 23rd February 2018, 08:05 PM
Stanton Stanton is offline
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Default Re: A naive, possible, safety idea

Hi Richard/Bonky

I had similar concerns when it came to testing my WD KT88. I have heard or seen it said that if you put one hand in your pocket while testing any shock will go down the side of your body to earth via your leg rather than from arm to arm via your heart when you use two hands. Sounds reasonable to me. Despite that advice, being inexperienced of working with such high voltages, I bought a pair of electrical insulating gloves to wear while testing. It was about six years ago but I think they were around £50 at the time. Seamed like a sensible investment in my future life at the time.

Have a good build,

Frank
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  #5  
Old 23rd February 2018, 09:25 PM
bob orbell bob orbell is offline
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Default Re: A naive, possible, safety idea

Yes, this is an interesting post, WAD supplied insulating gloves with their kits, perhaps we should see what Matthew has to say?, mind you £50.00 and as for shocks, well I have had my fair share , and I'm still here. BOB
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  #6  
Old 23rd February 2018, 11:20 PM
Stanton Stanton is offline
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Default Re: A naive, possible, safety idea

Your post has prompted me to look at the prices on the net Bob. Class 0 1000V which is the Class I bought can be found cheaper than when I bought mine six years ago. Seems they vary from £27 odd and upwards. A bit of shopping around may find them even cheaper.

Frank
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  #7  
Old 24th February 2018, 01:10 PM
Bonky Bonky is offline
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Default Re: A possibly naive safety idea...

Would thick Marigolds do? Is wearing Wellingtons a good idea?
R
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  #8  
Old 24th February 2018, 07:49 PM
Stanton Stanton is offline
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Default Re: A naive, possible, safety idea

I don't have any faith in Marigolds ability as insulating gloves. As a teenager I had an old banger of a car that misfired. I tried pulling the spark plug leads off one at a time to isolate which plug was a problem, trouble was the leads weren’t too good and I was getting shocks. Tried my mother's Marigolds and they made no difference. OK a car's spark plugs have a much higher HT than our amps but I wouldn't rely on them.

Regards Frank
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  #9  
Old 25th February 2018, 07:36 PM
John Caswell John Caswell is offline
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Default Re: A naive, possible, safety idea

Hi all,
Having spent a good few years building /fixing all sorts of electronic equipment here is my two penn'orth.
The sort of voltages that we deal with on this forum are dangerous, but that having been said, common sense/education is a good place to start and not protection, that can come later
The biggest danger when dealing with electrical power is if you get a path across both hands, as it will pass through the heart and that can be fatal - but not always, however it will give you one hell of a wakeup call.
The simplest way to stop this is the "one hand in the pocket" method, whereby the equipment is placed in a stable position so you are able to clip the lead of the DMM to chassis, without it falling over, and measure the other point with one hand holding the other DMM probe and the redundant hand firmly in your trouser pocket, it also helps if you are on/in some sort of insulating material/shoes. You will not need insulating gloves for this as there is no danger of providing a path through your body, even if the probe slips as you should be holding the insulated part (I hope).
As an aside it is quite safe using this method to touch live items with a bare finger providing you are not touching anything else earthed with the other hand. (I do not recommend doing this but a similar conversation came up very early in the forum.)
Low voltages i.e. below 50V do not present a hazard, which is why industrial/site transformers are 110Vac secondary centre tapped to earth i.e. 55-0-55V.
Always think about what you are to measure and how you want to measure it and engage brain!
Protective gloves like Marigolds are fine for the sort of voltages we deal with, frankly I have never used any sort of protection even when working live chassis Tv and also on colour and projection TVs where the EHT is 25KV.
The reason that Stanton received a jazz up on the car is simple. To get a spark to jump 25thou at a pressure of 20 atmospheres, say 300lbs/sq inch, requires a lot of volts, probably about 30KV, and that would comfortably have exceeded the dielectric breakdown strength of the Marigolds.
Try not to get paranoid about safety as this will lead you to taking to your bed and dying of bed sores
Think carefully about what you want to measure and how you are going to go about it. If in doubt ask here - most of us have been there and got the tee shirt.

John
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  #10  
Old 28th February 2018, 12:29 AM
Bonky Bonky is offline
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Default Re: A naive, possible, safety idea

Thanks John; informative, useful and 'comforting'.

I'll try!

BW

Richard
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