strange tube

[adalin]

Hi

bought some tubes and got a strange fellow in the box



the manufacturer is RADIOAG (~) DSLOEWE
they where big on tubes in the 193x i believe

In the top there is a small chamber, its not connected to the inside of the tube, in the chamber there is what I believe to be oil ?



The inside of the tube is not that big, just alot of glass



What is this? and why the chamber on top?

[astouffer]

You could try looking around www.r-type.org or www.tubecollector.org and see if theres anything similar. The side chamber might be for mercury, but thats my best guess

[Miles Prower]

Originally posted by adalin
In the top there is a small chamber, its not connected to the inside of the tube, in the chamber there is what I believe to be oil ?

Probably is, from an oil based condensation pump used during pump-down. Oil was cheaper than mercury, and a good deal less potentially dangerous in case the pump imploded. Of course, in those days, they didn't have the ultra low vapour pressure vacuum oils that we have today.

What is this? and why the chamber on top?

Looks like that was intended to operate as a "cold finger" to condense oil vapours coming from the condensation pump to keep them out of the tube itself.

[adalin]

Hmm so the oil was just there to get a better vaccum in the tube?

but why? there where tubes made in these days without the oil

Or is this tube some sort of hardvaccum tube, and how old is this tube based on the construction if this is the case?

So if this is correct the little chamber was cooled during sealing creating a underpressure sucking in the oil that was escaping from the pump?

I was misstaken before in one point, its not the anode that leads out o the top, its one of the grids, the tube got two grids, and an extremely thin single heaterwire in the center, no catode.

all in a circular mounting

Its printed BP1100 at the base

[The-Planet]

Loewe made a series of multivalve tubes - and I suspect this is one of them.

Sort of the original IC.

Look at Loewe Multi-valves for one example.

They are rare, and quite collectable in the radio world.

You might inquire over at the Tube Collectors Association on Yahoo. It's a very knowledgable group.

- Gary Tube WebStuff

[Miles Prower]

Originally posted by adalin
Hmm so the oil was just there to get a better vaccum in the tube?

Not really. A mechanical pump can't pull a good enough vacuum for a VT all by itself. It requires the assistance of a condensation pump. This works by creating a vapour barrier between the exhaust manifold and the mechanical pump. Air molecules can pass from the manifold to the mechanical pump side of the barrier, but not go back in the other direction. Molecular drag also plays a secondary role in improving the vacuum. However, some oil vapour will find its way into the exhaust manifold if you don't use a cold trap.

but why? there where tubes made in these days without the oil

They still use condensation pumps. Although why they didn't use a cold trap on the manifold, instead of on each tube is a strange one indeed.