Only if you inhale it.

New one on me. I want to know the answer myself.

Larry

A clue:
http://trade.mar.cx/US71528157

google gives lots of hits, but I can't find anything that talks about what the circuit is.

Wheelco made industrial boiler controls.Maybe that tube
came out of one of their controllers.Not sure why it says
danger on the tube though.I don't think the voltages in
the controller were much higher than what you would
find in a typical industrial setting.The tube itself is probably
no more poisonous than a regular receiving tube.Perhaps
they were concerned that if the tube was broken while
in use it could cause the boiler to go into thermal runaway.
Regards,
Swanson

Makes sense to me...

L

Wheelco used two functionally equivalent tubes for this. One mainly finds 5608A tubes, but they also used type 53 tubes.

Jim Cross

Last year, I found a box of NOS type 53 tubes at a flea market. Some had Wheelco labels and the box referred to furnace and boiler controls.

I sold most of them on the ARF Classifieds. It's a dual-triode with no mercury or strange substances.





Rich

My dad had some of these tubes and some paperwork about 40 years ago. He must have tossed them shortly after.
The danger warning appears to be only a ploy to make the tube look special, and that it couldn't be replaced with a radio tube or vice versa, but I still wouldn't have it for lunch.

Probably more of a reliability issue seen with many critical safety components.

Something on the order of "When renewing, insist upon (brand) tubes".

The 280 EIA code on the tube in question, indicates it was mfg'd by Raytheon...


Tom

No these controls generally operated the dampers, and prevented the waste of fuel through inefficient combustion. The controller generally included a photocell which checked the density of the smoke, and would open a damper when the smoke contained too much soot. This simple system was generally used on hand-fired boilers, as an alternative to having a fireman walk outside and inspect the plume of smoke coming out of the stack.

More sophisticated systems would also control the rate of firing by an automatic stoker.

Never did they control pressure.

These systems became almost mandatory in the large cities after the War, as local ordinances were passed against the production of choking smoke. Those born after the advent of the Clean Air act little remember the situation of many of our industrial cities. In Pittsburgh, in 1905, virtually all of the trees died due to pollution. The death rates from cardiovascular and respiratory causes were severely elevated in our smoky cities.

Then, in the early 1950's came local ordinances against the emission of visible smoke, and the general application of the Cottrell Precipitator, which though it had been available since the turn of the century, was relatively little used until the law demanded. After this, the pollution of the atmosphere continued apace, but only with invisible pollutants, not with visible soot. The smogs of the 1960's were created by photoreactive invisible pollutants, which became visible after being acted on by the atmosphere and by sunlight.


Here is downtown Pittsburgh at 10:55AM on a damp day in May, 1940:


Around Noon, on a sunny day in January, 1940:



10:35AM, November 1939:


it wasn't just Pittsburg. St Louis, 9:40 AM, October, 1940:



These tubes helped control the choking smoke.

I have 2 Raytheon 171A type triodes, that has the name RAYTHEON stamped in raised letters, on the tube plate. Neat looking.

During this heavy smog the moths that had a darker color to blend with the dirty wood they landed on survived and the the light colored ones were eaten by the birds. After Pburgh was cleaned up the dark ones go eaten and the ligthly colored one thrived on the cleaner wood.

I remember that mentioned in my high school biology book. That was in the 70's. I've seen photos of LA from that period, and just assumed LA had a monopoly on smog. Guess not. Though going back to the 70's, the smog level back then was a lot worse, than I've seen it in recent years. There use to be days, when I thought I was living on Mars. Reddish-orange sky, with a visibility of only a few hundred feet. Also it was too hot and dry to be fog. Haven't seen that in decades.

In the '60s and '70s Pittsburgh was still fairly nasty. The coke ovens and steel mills shut down and, since then, it has cleaned up a lot. As well, Morgantown WV is no longer constantly black from coal dust. In early spring the trees would get washed by rain. That was the only time that they would show as being bright green. I remember being in Chicago, during '76 or so, when a "thermal inversion" trapped the smog over the city for weeks. It, too, was like a scene from a Tolkein novel.
Also, in the earlier years, the old growth forest were cut to make charcoal for the processing of iron. Ever make charcoal the old way (without a retort)? Super smokey!