Ignoramus27088 wrote:
Got myself some capacitors for $10 apiece.

http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7603382621

The specs are 22 kV, 1 uF, discharge capacitor. See

http://igor.chudov.com/tmp/cap.jpg

The seller was wrong in describing them as 22 VOLT capacitors. They
are 22 KILO volt capacitors. (the seller is Fermilab).

They are similar to this one:

http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7598631638

but have twice more capacitance.

Anyway, here is my question. I have a 9 kV DC power supply. (a
Franceformer). How can I safely test these caps before selling
them. At 22 kV, they can store about as much energy as a .22 bullet,
according to my calculations.

It would be less at 9 kV, but still, obviously, very deadly.

So. What is a safe way to charge them, verify that they hold the
charge, and then DIScharge them at 9 kV.

i


Unmless you are going to test them to 80% of their maximum voltage
rating or to their full working voltage, I wouldn't describe them as
tested for resale. You'd be better off checking them at say 1KV and
then selling them as untested but belived working with a (short) warrenty.

I wouldn't even want to ship or store them without shorting straps
accross each one.

If you do decide to do the high voltage testing, a TV LOPT commonly
operates at up to about 27KV but the tube has typically 1/100 of the
capacitance. A TV EHT probe or meter is easily capable of measuring
these voltages safely, though personally I'd want to set it up in a
grounded clamp stand so I wasn't hand holding it.

Discharging them safely is going to be a real problem. The obvious
approach is a series chain on high voltage high power resistors in an
insulating tube that is good to at least 30KV. Maybe a chain of bleeder
resistors from microwave ovens? However I'd want specialist advice
myself. Why not ask on sci.electronics.repair. Do you have a drum of
suitably rated EHT cable? If not you cant really make ANY connections
safely to them.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk [at]=@, [dash]=- &
[dot]=.
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"Ian Malcolm" wrote in message
...

Discharging them safely is going to be a real problem. The obvious
approach is a series chain on high voltage high power resistors in an
insulating tube that is good to at least 30KV. Maybe a chain of bleeder
resistors from microwave ovens? However I'd want specialist advice myself.
Why not ask on sci.electronics.repair. Do you have a drum of suitably
rated EHT cable? If not you cant really make ANY connections safely to
them.

It's really, really fun to drop them in a bucket of water while fully
chargedG.

Actually, it doesn't do much, but you get a nice crack and a cloud of steam
each time.

We did that at the Transitron lab because the engineering department was too
cheap to spring for a high voltage bleeder array. Not that it would've
cost much, but they didn't want to use up "valuable bench space".

Now... dropping a wet paper towel across the terminals -- THAT's fun!

LLoyd

For some reason to do with silly things to do with science this reminded
me of the glass phenomenon called "prince rupert drop"
http://en.wikipedia.org/wiki/Prince_Rupert's_Drop , if you see a glass
blowing demo then ask about it maybe they will show you. If your brave
then have one go of in your hand, numbs it for a minute or so but much
like catching a baseball incorrectly.

Lloyd E. Sponenburgh wrote:

"Ian Malcolm" wrote in message
...

Discharging them safely is going to be a real problem. The obvious
approach is a series chain on high voltage high power resistors in an
insulating tube that is good to at least 30KV. Maybe a chain of bleeder
resistors from microwave ovens? However I'd want specialist advice myself.
Why not ask on sci.electronics.repair. Do you have a drum of suitably
rated EHT cable? If not you cant really make ANY connections safely to
them.


It's really, really fun to drop them in a bucket of water while fully
chargedG.

Actually, it doesn't do much, but you get a nice crack and a cloud of steam
each time.

We did that at the Transitron lab because the engineering department was too
cheap to spring for a high voltage bleeder array. Not that it would've
cost much, but they didn't want to use up "valuable bench space".

Now... dropping a wet paper towel across the terminals -- THAT's fun!

LLoyd

Ignoramus27088 wrote:

After looking at HV resistors on ebay, I realized that I may have a
couple in my junk pile (pieces from a radar test set). Will check
tonight. There are probably 5 kV rated, but I could put 2 in series.

i

For the discharge resistor, leave your self some margin. If 5KV rated,
put three identical ones in series if you are testing at 9 to 10 KV.

What procedure are you proposing to non violently check the caps are
actually discharged? Personally I'd want to know they were fully
discharged (well past 99%) before handling them. Also does your plan
include checking the HV probe after use before relying on it to indicate
they are safe?

Insulation can be a problem, beware of surface leakage, all surfaces
need to be extremely clean and absolutely dry. I've used glass up to
about 35KV with a grounded guard ring (in case there is a flaw I haven't
spotted) with no trouble so if you have a large enough quartz glass tube
that should be suitable to hold the resistors. Some uncolored plastics
are also suitable for high voltage work. There is no way you'd get me
using wood unless it was freshly kiln dried then vacuum impregnated with
paraffin wax. Corona discharge can also be a real problem. It
shouldn't be TOO bad at 10KV but you still want to be really carefull to
get nice smooth connections with no sharp edges or points.

High voltage har a really annoying way of finding the slightest
weakness or pinhole in any insulation and many TVs have had a fine
fireworks display from the side of the LOPT on my bench. Its a bit
inconvenient if one is just trying to get the TV powered up successfully
to decide if its condition is good enough to justify LOPT replacement
but with your setup it's potentially lethal. Its also important to
confirm the integrity of the grounding wires in your test circuit. I
left off the ground lead to the aquadag on a large screen TV by mistake
ONCE, (in 12 years) now I'm rather cautious. You goof up your grouding,
yoy'd better allready have got a good deal on a pine box . . .


Wild wacky and way out there idea!! Does anyone have any idea if a
suitable length of carbon core vehicle ignition cable would make a
satisfactory bleeder resistor? Iggy would be dumping 100 joules into
it, its got distributed resistance and sufficient insulation so the main
worry is can a maneagable length take the peak power?
--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk [at]=@, [dash]=- &
[dot]=.
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Ian Malcolm wrote:

Wild wacky and way out there idea!! Does anyone have any idea if a
suitable length of carbon core vehicle ignition cable would make a
satisfactory bleeder resistor? Iggy would be dumping 100 joules into
it, its got distributed resistance and sufficient insulation so the main
worry is can a maneagable length take the peak power?
AARGH 1/2*CV^2 so 50 joules for 10KV (up too late!). Hmm, carbon core
cable is even more appealing to me.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk [at]=@, [dash]=- &
[dot]=.
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Ignoramus27088 wrote:

Ian, would you or anyone have any idea if what I have is HV resistors?


They are blue, about 3 inches long, and are marked VICTOREEN MOX-3 12
MEG.


Yup, that's the cream of the crop! I can't give you ratings off the
top of my head, but a few of them in series should definitely handle
10 KV.

Jon

On Thu, 30 Mar 2006 21:36:18 -0600, Jon Elson wrote:
Ignoramus27088 wrote:

Ian, would you or anyone have any idea if what I have is HV resistors?


They are blue, about 3 inches long, and are marked VICTOREEN MOX-3 12
MEG.


Yup, that's the cream of the crop! I can't give you ratings off the
top of my head, but a few of them in series should definitely handle
10 KV.

Cool. They came from a radar test set. It actually had a 5kV DC power
supply (xfmr plus bridge rectifier), but, alas, I sold the
rectifier.

i

On Fri, 31 Mar 2006 02:49:16 GMT, Ignoramus27088
Gave us:

Ian, would you or anyone have any idea if what I have is HV resistors?


They are blue, about 3 inches long, and are marked VICTOREEN MOX-3 12
MEG.

Those are HV resistors. At least I'd say it is quite likely.
Probably 15kV or higher rating. They are Metal Oxide, likely 3 Watt
units. Without actually hunting up the data sheet from victoreen, it
is no more than an educated guess, however.

In article ,
Ignoramus27088 wrote:

Ian, would you or anyone have any idea if what I have is HV resistors?


They are blue, about 3 inches long, and are marked VICTOREEN MOX-3 12
MEG.

You need to get a collection of EEM catalogs. Back in the 1993 edition,
the Victoreen pages in the Resistor section says that it's most
likely a MAXI-MOX rated at 22.5 kV. Rated at 4.5 watts if it's a
MOX-3-13, epoxy coated or 7.5 watts for a MOX-3-12 silicone coated.

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)

On Fri, 31 Mar 2006 22:09:18 GMT, Mark Zenier wrote:
In article ,
Ignoramus27088 wrote:

Ian, would you or anyone have any idea if what I have is HV resistors?


They are blue, about 3 inches long, and are marked VICTOREEN MOX-3 12
MEG.

You need to get a collection of EEM catalogs. Back in the 1993 edition,
the Victoreen pages in the Resistor section says that it's most
likely a MAXI-MOX rated at 22.5 kV. Rated at 4.5 watts if it's a
MOX-3-13, epoxy coated or 7.5 watts for a MOX-3-12 silicone coated.


Mark, thank you VERY much for looking it up.

i