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Can anyone help with info on this great find ??

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LAN_403

radiotech

Thu Jul 15 2010, 07:59PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
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Posts: 1546

If you can trace the heater wiring of the 6AL5, see if it is connected in series with any resistors 10 or 15 ohms on its way back to the transformer.

Adam Munich

Thu Jul 15 2010, 10:30PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Wow, forget the vacuum caps, that diode is a much bigger X-ray hazard!

Also, as i posted before, if the glass is heavier than it should be, it may be leaded.

IntraWinding

Fri Jul 16 2010, 02:42AM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

Grenadier wrote ...

I doubt any parasitic capacitance from lead .5" away still separated by the glass tube would be significant.

But a 1/2" is only about double the gap in the vacuum capacitors, so I think it could make a big difference. And any corona leakage could screw with the measured voltage too. Anyway, I guess once you have a stable voltage to measure it's easy enough to try it and see..

Adam Munich

Fri Jul 16 2010, 03:20AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

^^ The cap gap only appears to be a few mm.

klugesmith

Fri Jul 16 2010, 03:42AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Why are so many people here looking for an x-ray hazard in ordinary vacuum capacitors? I did read the whole thread, but still stand with plazmatron in being relatively unconcerned.

X-ray production mechanisms and dose limits were well understood when Sparky's enviable instrument was made.
Field emission from smooth copper electrodes requires E-fields of about 1000 volts per micron.
Flash x-ray tubes have cold cathodes that are sharp points, working at over 100 kV.

[edit] and I wouldn't be surprised if Sparky's caps are rated for just 50 kV each, with the 100 kV range being only for differential mode.

Adam Munich

Fri Jul 16 2010, 03:59AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

What about the Diode? At 100kv, the sheet metal will do very little to stop x-rays. It's a heated cathode diode, and essentially a Coolidge tube at those voltages.

Unless his diode is biased with substantially lower voltages, however i really have no idea how it's hooked up. If it is passing the full voltage though, it is definitely a hazard.

klugesmith

Fri Jul 16 2010, 04:00AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Grenadier wrote ...

What about the Diode? At 100kv, the sheet metal will do very little to stop x-rays. It's a heated cathode diode, and essentially a Coolidge tube at those voltages.

Why would any voltages more than 1 kV ever appear below the glass vacuum capacitors? The instrument is a capacitive voltage divider like the one Patrick (?) had been designing.

Adam Munich

Fri Jul 16 2010, 04:02AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Damn, you caught my ninja edit.
Alright then, good luck sparky! I'd still invest in a scintillator though.

OH7HJ

Sun Jun 12 2011, 06:32AM

Registered Member #3942 Joined: Sun Jun 12 2011, 06:00AM
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Posts: 1

sparky99 wrote ...

Hi All,

... I sure would like to have a manual for it, but there is little online. Anyone have any info on this gem. A search of Jennings website turns up nothing...

Thanks,

bob

Hi!

I would like to find a schematic for the Jennings J-1003 broadband AC high voltage meter, too, particularly to see how the 'unbal' mode of its selector is connected to further understand how it works.

The meter works very well - AC only, no DC with capacitive voltage dividers like this - and does not noticeably strain even those delicate microampere level circuits I regularly measure in about 20 kV electrostatic environment.

I clearly see that the 2.8 pF voltage dividing VDF-2.8 vacuum capacitor tubes consume practically no power from the measured circuits so they can not produce any measurable X-ray emissions, either.

The real challenge remains to find its schematic and manual! Here are some links to it but no manual or schematic there:

Regards,

- OH7HJ -

Finland
plasma.innoplaza.net

Here are some photos of the Jennings J-1003 high voltage AC meter I am using:

Carl Pugh

Sun Jun 12 2011, 05:27PM

Registered Member #1064 Joined: Tue Oct 16 2007, 05:04PM
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Posts: 42

MANY years ago Ross Engineering Corporation in Campbell CA made an identical voltmeter.
Mr. Hugh Ross would probably be willing to discuss the voltmeter if you gave him a phone call.

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