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#28750 - 08/29/03 12:54 PM Old electronic tube testers
Joe Carpenter Offline
Member

Registered: 12/19/01
Posts: 55
Loc: USA
Not excatly an electrical question. However, I recently got a hold of 3 old tube testers. 2 are in wooden boxes with covers and one is in in a metal box with no cover. Does anyone know anything about these? They have a scroll built into them with all the different tubes listed and what to set the switches at to test them. I can get make and model if that would be helpful.
I thought they were rather interesting pcs.

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#28751 - 08/29/03 01:04 PM Re: Old electronic tube testers
Bill Addiss Offline
Member

Registered: 10/07/00
Posts: 4196
Loc: NY, USA
Can you get some pictures?
We'll post them here.

If so, send them to:
photos@Electrical-Contractor.net

Bill

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#28752 - 08/29/03 01:09 PM Re: Old electronic tube testers
NJwirenut Offline
Member

Registered: 09/15/01
Posts: 816
Loc: Bergen County, NJ
What exactly do you want to know about them?

Tube testers fall into 2 general categories: emission testers and mutual conductance testers.

The emission testers were much cheaper, simpler, and more limited in their usefullness. They would identify a tube that was burned out or completely used up, but that's about it. Cheaper TV service testers, as well as the once ubiquitous drugstore self-serve testers were all emission type. They basically tie all the elements except the cathode in the tube to the plate, and test the tube as a simple diode. They can actually damage some low-power tubes by forcing too much current through the grids.

Mutual conductance testers are much more sophisticated, and give a better picture of tube quality. They generally set the tube up as an amplifier, and measure the change in plate current caused by a change in grid voltage (transconductance or Gm). These testers were more complex to set up (lots of switches and knobs!), but could find more subtle tube defects than a simple emission test.

If you can post makes and model numbers, I can probably tell you what type you have. A great reference on tube tester technology is "Tube Testers and Vintage Electronic Test Equipment" by Alan Douglas. The author (as well as a few ECN members including myself) are regulars on the USEnet newsgroup rec.antiques.radio+phono, which is a great resource for questions on tube era equipment.

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#28753 - 08/29/03 01:18 PM Re: Old electronic tube testers
yomomma Offline
Junior Member

Registered: 08/24/03
Posts: 2
Loc: Arlington, Texas, USA
Sure, but when playing with them, keep in mind they have a high voltage (sometimes up to 800v) for the heater portion of the tube. The low voltage parts act like the collector, emitter, and base (or valve/gate) of a transistor. Once the base is heated up to the point that it can emit electrons internally, the various switches on the tester change the bias on the gate and allow (or stop) signal to pass through.

Most of the guys that have one (or some) of these usually clean them up and park them in some unused part of their lab/office. Sort of a novelty wall hanger.

(mho) Not a lot of current-day use unless you are into old time radio equipment, or maybe some sort of Dale Gribble survivalist.
Some of those guys keep old tube radios and equipment around for the day the Commies (etc.,) (insert favorite boogieman) attack.

I guess if you wish to find the market/values I would look on ebay and other such sites.

See you,

Phil

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#28754 - 08/29/03 01:19 PM Re: Old electronic tube testers
classicsat Offline
Member

Registered: 11/23/02
Posts: 449
I have an old one, a Swan I beleve, that was once owned by the Navy.

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#28755 - 08/29/03 01:34 PM Re: Old electronic tube testers
NJwirenut Offline
Member

Registered: 09/15/01
Posts: 816
Loc: Bergen County, NJ
 Quote:
Sure, but when playing with them, keep in mind they have a high voltage (sometimes up to 800v) for the heater portion of the tube.


The heater of a tube generally operates on LOW voltage (typically 6.3 VAC), although a handful of types operated directly from 117V line voltage.

 Quote:
The low voltage parts act like the collector, emitter, and base (or valve/gate) of a transistor.


Actually, being a voltage-operated device, a tube is more analogous to an N-channel depletion mode MOSFET than a bipolar transistor. The element correspondences would be cathode=source, grid=gate, and plate=drain. And in most tubes, the plate is anything but a "low voltage" element, operating at hundreds or even thousands of volts!

 Quote:
Once the base is heated up to the point that it can emit electrons internally, the various switches on the tester change the bias on the gate and allow (or stop) signal to pass through.


On a bipolar transistor, the base would be analogous to the GRID, not the heated cathode, which is the electron source. The emitter would be the equivalent to the cathode.

 Quote:
Most of the guys that have one (or some) of these usually clean them up and park them in some unused part of their lab/office. Sort of a novelty wall hanger.


Mine sees somewhat regular use, but I restore old radios and test gear as a hobby. I also collect tubes themselves (mostly big transmitting types) as another aspect of the hobby.


[This message has been edited by NJwirenut (edited 08-29-2003).]

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#28756 - 08/29/03 01:46 PM Re: Old electronic tube testers
SvenNYC Offline
Member

Registered: 08/19/02
Posts: 1685
Loc: New York City
The best place (among others) to go for information is the Antique Radio + Phono UseNet news group.

It's accessible through http://groups.google.com -- just type rec.antiques.radio+phono in the box. You have to subscribe to post but it's no big deal.

By all means post the pictures here (or on a separate website) -- and you can steer the people there to look for them at the website since you can't post pictures on that newsgroup.

Good luck!!!

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#28757 - 08/29/03 05:22 PM Re: Old electronic tube testers
LK Offline

Member

Registered: 01/21/03
Posts: 1721
Loc: New Jersey
Wirenut,
Don't you just love the smell and crackel sounds of old tube equipment.
WB2OMS

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#28758 - 08/29/03 09:47 PM Re: Old electronic tube testers
NJwirenut Offline
Member

Registered: 09/15/01
Posts: 816
Loc: Bergen County, NJ
Absolutely. The older equipment has a "soul" that modern solid state stuff somehow lacks.

Just about to begin restoration work on an R-390A/URR HF receiver. A masterpiece of tube era engineering. Digital frequency readout using an odometer-style counter and more gears and cams than a automotive transmission. Should be lotsa fun!
http://www.r390a.com/index.htm

Real Radios Glow in the Dark!
http://www.ominous-valve.com/tubes.html

73,
Bob N2IXK

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#28759 - 08/30/03 03:20 AM Re: Old electronic tube testers
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
 Quote:
Absolutely. The older equipment has a "soul" that modern solid state stuff somehow lacks.

Well said, Sir!

Regulars here will know that I'm also a fan old of equipment and often have tube radios, amplifiers, etc. that I restore.

These tube testers (or in British terminology, "Valve testers") come in many varieties. Some of the most sought after in Britain and the series made by Avo. Some models sell on eBay now for figures well up into three digits.

As for the voltages involved, I'll just echo what others have beaten me to saying. The plate voltages, especially on high-power tubes can be high, and testers designed for those tubes will output HT at hundreds of volts and a good few ten of milliamps, so be careful!

Famous Last Words #287: "Of course the top cap is the grid!"

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