In the early 90's I dreamed up an alien sci-fi technology that had never invented transistors, instead they made repairable integrated tube circuits for their spacecraft by soldering the elements onto a printed substrate in a large chamber ventilated to space. When the gain decreased they repainted all the cathodes with Caesium or Radium in an Argon glove box.
I mentioned the idea to an engineer at work (Mitre) who told me about ongoing research in that direction.
-jsw
Wild idea. Tightly vented, so as to avoid space dust?
?
Wilder still to find out it was happening, and at super high freqs, wot? Cool.
Thanks.
With the dual caps, if one blows it rips the connection loose for the other thus your pump stops if the fan cap blows. How can you duplicate that protection?
For the time machine?
Tom Gardner fired this volley in news:mr7c7b$ob4$1 @speranza.aioe.org:
Tom, they most often fail by another mechanism. Most often, they just lose capacity until they no longer will start their associated motor.
That "protection" is accidental, anyway. "Blowing" is less often seen than just "venting", and they don't tear themselves apart mechanically when they vent.
Adding protection for a bad compressor start would be easy enough... when they don't start, they kick their over-temp switch, and that signal could be used to turn off a latching relay on the fan circuit.
Adding protection in the opposite case would be harder, since most fan motors are just split-phase induction motors, and if they have any thermal protection at all, it's internal. You'd have to add some sort of 'air motion sensing' to manage that one.
Lloyd
Yes we know two with one blow. However both are by the same guy that made them with faulty paper or seals. So both are in the trash.
It is for design and space. Often > >> Tom Gardner fired this volley in news:mqufgp$qs1$2
Actually the start cap if dry won't start the motor well. The cap is in series with the start winding and a switch. There is enough working to start a slow ramp up to speed and once there have power.
The start cap is a reactive negative resistance to the coil's positive resistance. (reactance really). A tug on a rope start and it will turn over faster and catch.
Some caps have fuses > Tom Gardner fired this volley in news:mr7c7b$ob4$1
Who cares whether the fan runs all by itself? That won't hurt anything. What would be nice would be for the compressor to lock itself out rather than keep cycling on its over-temp limit.
Exactly, Bob. That's what scared me when mine died. I did NOT want to lose that pump!
No, for the chroma circuit on every cheap assed tube type color TV. You could find up to seven bad tubes in a single TV. :(
The time machine used a Z80B. ;-)
Very few high power transmitters are tube, these days. They use multiple, identical solid state amplifiers that are mounted in slide in trays. The inputs are fed by an array of power dividers, and the outputs are combined with an array of combiners. This allows low skilled staff to be notified by the transmitter's computer which tray has failed, and for them to slide it out, and slide in the replacement. One of the few remaining sources is ENCO, who rebuilds some finals. Most of the OEM sources merged, or closed their doors. Richardson Electronics bought Eimac a long time ago. There used to be millions of cheap, surplus transmitter tubes, but some types haven't been available in decades.
When dealing with power short wave. I can believe the tray mode. Who designs their own transmitters anymore. Lost art.
Audio : Tubes for amplifiers 7,9, etc pin preamps and beam amps as well.
RF: Transmitter tubes that are very large are still made but users like us can't think of having one much less using one.
They are 20 some feet tall. Filaments are replaceable by climbing inside! Many are much smaller - 6' and 3' tall. Power in MW.
The big ones use liquid to cool and the pool glows in the dark...
Mart>
Martin, most new broadcast transmitters are all solid state. The last tube final transmitter I maintained used three 65 KW EEV Klystrons for a
5 MW EIRP output on NTSC TV ch. 55 with the antenna on a 1700' tower. It was a Comark, and was built around 1985. It was water cooled, along with the smaller RCA TTU25B that I used to build WMRX ch. 58 in Destin Florida.
I suspect that Jim Wilkins has pretty much covered it, but if you want more, send me a note and I will ask him for the list.
IIRC my Gradfathers first hearing aid had pencil tubes, along with a battery pack that he carried on his belt!
Those are small. But almost reasonable for a home rig :-)
Consider those that drive the largest phase array radar in the world ? How about those that drive the CERN toys.
Some of the 3' and 6' are used on linear accelerators to make radioactive isotopes for treatments and machines.
Then there are those along the long SLAC that drives beams near the speed of light. Big stuff.
The largest ones - the base commander had a pair placed at the front gate like missiles. Seems the maker, a large mil company, got the mechanical specs inside off. They were to big to ship back and the plant used them as stick in the eye of the local rep every day. No longer there and the plant outside area is a bit different.
You know they are big when you can unbolt the side plate to replace the filament. Naturally you are in a hard RAD suit at the time.
Mart>
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