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Author Topic: What the heck do you do with a 400meg 200 watt resistor?  (Read 5186 times)
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N0WEK
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« on: January 31, 2014, 12:22:14 PM »

On my recent visit to the now closed Black Hole in Las Alamos, NM I got a pile of 200 watt resistors along with some other misc. parts.

5 of the 23 resistors are useful values but 18 of them are 5 meg through 400 meg, with 7 of them being 100 meg.

What the heck can you do with these values? They must have been part of some really high voltage piece of equipment. About half of these are NOS.

Any ideas?
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W7TFO
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« Reply #1 on: January 31, 2014, 12:27:29 PM »

One sees a lot of that type Ohm in atomic research gear.

You can use any even-Megohm (easier) resistor along with any 0-1mADC meter for Volts:  5 meg = 5 kV full scale.  A little large, but since you already got 'em...

I have a 1-Gigaohm job.  Might as well be an insulator...

73DG
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N0WEK
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« Reply #2 on: January 31, 2014, 01:06:41 PM »

One sees a lot of that type Ohm in atomic research gear.

You can use any even-Megohm (easier) resistor along with any 0-1mADC meter for Volts:  5 meg = 5 kV full scale.  A little large, but sine you already got 'em...

I have a 1-Gigaohm job.  Might as well be an insulator...

73DG

True...these things are like fat, foot long hot dogs.  I hate to think what they cost the lab, although these are 10-20% jobs, not the 1%ers!
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« Reply #3 on: January 31, 2014, 01:40:51 PM »

Good for calibration of hi-pot gear.

Check out the prices on those resistors. Lots of zeros just like the resistance  Grin
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« Reply #4 on: January 31, 2014, 02:32:04 PM »

You could always build an EMP simulator or a high powered laser.  Grin

Phil - AC0OB
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AB2EZ
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« Reply #5 on: January 31, 2014, 03:50:59 PM »

Use it as a bleeder resistor for a 275,000V B+ supply with a 0.1uF output filter capacitor*.

*Use 1000 well-matched capacitors in series: each 100uF, rated 450V at 105C... with a 1M ohm 1 watt balancing resistor across each one.

With a 10mA load, and assuming a 60Hz single phase full wave rectifier (capacitor input), you will have only about 833V peak-to-peak ripple (0.3%).

275,000V x 10mA = 2750W. This is enough to power a legal limit linear amplifier.

Stu
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« Reply #6 on: January 31, 2014, 04:45:36 PM »

275,000V x 10mA = 2750W. This is enough to power a legal limit plate modulated linear amplifier.

Stu

OK, you're bringing the tubes... Wink

73DG
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« Reply #7 on: January 31, 2014, 04:52:37 PM »

275,000V x 10mA = 2750W. This is enough to power a legal limit plate modulated linear amplifier.

Stu

easy does it on the ozone
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AB2EZ
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"Season's Greetings" looks okay to me...


« Reply #8 on: January 31, 2014, 05:06:58 PM »

Basically you can use a modified 2750V-rated triode design, where the filament, cathode, and grid structure are unchanged... but the distance between the cathode and the plate is scaled up by a factor of 100 (to keep the E-field the same). The modified tube will be around 15 cm long, and about 50 cm in diameter.

Stu

Quote from: AB2EZ link=topic=E35692.msg274851#msg274851 date=1391201459
275,000V x 10mA = 2750W. This is enough to power a legal limit linear amplifier.

Stu

OK, you're bringing the tubes... Wink

73DG
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« Reply #9 on: January 31, 2014, 05:30:56 PM »

P.S.

It is important to note that the electrons that strike the plate will have an energy of 275,000 electron volts. Therefore sufficient hard X-ray shielding around the tube will be required.

Be alert to signs of radiation poisoning... such as increased hair loss when operating the rig; and increase the thickness of the shielding if this occurs.

Candidate shielding materials include: lead, depleted uranium, and top soil from any of a number of new developments in NJ.

Stu
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N0WEK
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« Reply #10 on: January 31, 2014, 06:15:01 PM »

You could always build an EMP simulator or a high powered laser.  Grin

Phil - AC0OB

My guess is that they were doing something like that at the Las Alamos labs where these came from.

The 4 mfd 600 volt Aerovox oil caps all checked good with an ohm meter which is all I had available...Model 610M cans.

I also got a bunch of male and female chassis mount 120 vac sockets which will be a nice way to get power into so projects.

I may stop up there again in a couple of weeks when I get back to NM.
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« Reply #11 on: January 31, 2014, 07:21:11 PM »

Must have been used in some REALLY HIGH VOLTAGE measurement system.  I have a volt meter from a Gates BC-1T and the dropping resistor is 3 megs mounted with clips on insulators.  I built the dropping resistor and meter on a small chassis and use it for my HV supply testing.  Whatever those bugs were used for must have been the things great science fiction devices could have been!   Shocked
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