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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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Old 4th Jun 2021, 4:37 pm   #1
nigelr2000
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Default How's this for a strange device

Found this in a drawer today when looking for a new laser. had it ages it came in a load of stuff from an old ships radio technician and Ham radio guy at least 20 years ago when I had a shop he thought I would find it useful

I wonder how accurate it would be never mind it qualities as a spark transmitter
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Old 4th Jun 2021, 5:15 pm   #2
Paul_RK
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Default Re: How's this for a strange device

I've not met one in the flesh, but seeing the name reminded me that the device was regularly advertised in Practical Television at one time as the "Radar Kilovolter": produced, according to the Science Museum online, from 1950 to 1974.

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Old 4th Jun 2021, 5:31 pm   #3
TowerRadio
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Default Re: How's this for a strange device

The mark 2 may have an extended range to cope with colour EHT levels.My father had one,earlier model the transparent case always looked to me as if it was made from celluloid!Les.
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Old 4th Jun 2021, 5:42 pm   #4
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Default Re: How's this for a strange device

Quote:
Originally Posted by TowerRadio View Post
...the transparent case always looked to me as if it was made from celluloid!Les.
Seems it is.

https://collection.sciencemuseumgrou...eter-voltmeter
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Old 4th Jun 2021, 5:57 pm   #5
Cruisin Marine
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Default Re: How's this for a strange device

It reminds me of the old Flashtest devices used for car EHT testing, but considerably more elegant in build than the flashtest which was a piece of plastic with opening like dividers, and a small piece of metal either side to see how far the EHT spark would flow.
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Old 4th Jun 2021, 6:04 pm   #6
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Default Re: How's this for a strange device

Quote:
Originally Posted by nigelr2000 View Post
... I wonder how accurate it would be ...
I wouldn't trust it to better than +/-10-20%.

In a previous life I used kilovolt (and indeed megavolt) spark gaps in the high-power laser equipment I worked with. Some of the gaps were DC-charged, as this one would be, but most were pulse-charged. Counter-intuitively perhaps, the pulse-charged ones were a good deal more reliable than the DC-charged ones (but whenever we possibly could, we tried to trigger all of them).

Things which can cause DC-charged gaps to 'go early' include: changes in air pressure and humidity, contamination and damage (even at very small scale) on the electrode surfaces, surface tracking on the gap's insulator (it makes UV light which photoionises the gas in the gap), cosmic rays (gas breakdown is used in the 'spark chamber' detector e.g. https://www.youtube.com/watch?v=nvvW9chTxH4) etc, etc.

Cheers,

GJ
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Old 4th Jun 2021, 6:15 pm   #7
Dave Moll
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Default Re: How's this for a strange device

Many years back I acquired one of those Kilovolter devices, but to be honest I never had the courage to put it anywhere near the EHT of a television set, though I still have it somewhere.

I later acquired the KHP-30 EHT probe pictured below, with which I felt far more comfortable.
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Old 5th Jun 2021, 3:53 am   #8
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Default Re: How's this for a strange device

I have a Radar Kilovolter too, I thought I started a thread about it some time ago. And I've never tried it on a TV EHT supply, not for my own safety but because all the units I work on (video monitors) have transistorised line output stages and drawing a spark from the EHT is not a good idea.

For measuring EHT I have the Heathkit EHT meter (one of only 2 Heathkits I've ever assembled).It's just a high-voltage 800M resistor and a 50uA meter in series, and thus reads to 40kV. I don't know how accurate it is, but most of the time I just want to check that EHT is present and roughly right (right enough that I should have something on the screen)
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Old 5th Jun 2021, 1:00 pm   #9
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Default Re: How's this for a strange device

Wise decision. Solid state TVs rendered this a museum curiosity.
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Old 5th Jun 2021, 1:21 pm   #10
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Default Re: How's this for a strange device

Yes I have one of these EHT testers too and likewise, never tried it! Think mine is the original one , not MK11.
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Old 6th Jun 2021, 7:53 am   #11
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Default Re: How's this for a strange device

Celluloid must have properties that made it suitable then..? (i recall it was a component of ad-hoc incendiary bombs!- but not the ignition source as such)

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Old 6th Jun 2021, 8:18 am   #12
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Smile Re: How's this for a strange device

Hi,
Back in around 1972 I worked in a radio & TV repair business. My boss had one of those and tried to check the EHT on a Bush transistorised TV set.
He was only ever used to valve tellies and, when it arced over, it wrote off the time bases, the sound board and probably the IF strip too. Oops!
This happened in the customer's house, and he sheepishly muttered: "It needs to go back to the workshop. Have a loan set."
Cheers, Pete.
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Old 6th Jun 2021, 8:45 am   #13
Dave Moll
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Default Re: How's this for a strange device

As this thread has progressed, I have become increasingly glad that I never used mine. It seems it was of as dubious utility as I feared. As I recall, I only bought it out of curiosity in the first place during my early tentative forays into eBay.
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Old 6th Jun 2021, 9:07 am   #14
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Default Re: How's this for a strange device

I had one when I was in my teens, and used it, once. No ill effects but only used for the amusement factor (!). I remember persuading my friends that once a spark had been enacted it was then stored in the device for use on - well, them! It's long since gone.
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Old 6th Jun 2021, 3:48 pm   #15
nigelr2000
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Default Re: How's this for a strange device

So this was a serious bit of kit and not a cheap K tel style tester you would get out the Sunday papers ad's. I too have never plucked up the courage to use it. Lucky really as by the time I entered the trade it was all transistor sets.
Think I will stick it back in it's drawer and let it rest for another 20 years
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Old 6th Jun 2021, 4:10 pm   #16
TonyDuell
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Default Re: How's this for a strange device

I am pretty sure it's mentioned in 'Television Receiver Servicing' by Spreadbury which I have always considered to be a 'serious' book.
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Old 10th Jun 2021, 8:52 pm   #17
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Default Re: How's this for a strange device

Brings back lots of memories we had one in the workshop were I started
back in the late 1950's. It was kept I a thick cardboard box and only used by
S/ Manger only . Just valve tv.s in those day's
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