What are these ?

[joebog1]

My turn to ask a question of the brains trust.
I have a mob of these "bits1".
I have never seen them before.
They seem to be a piece of carbon rod held in two endcaps, that are glued on:
SOME are not so well done. see pic "quality built".
A few of them have a single white dot, as per the pic "white_dot".
I have suspected they are inrush limiters from the 50's, because If I heat them while measuring resistance, the resistance drops quickly and markedly, when I direct my heatshrink torch ( LPG gas tiny torch) onto them.
There are two sizes shown, but there is very little difference between them, apart from resistance, those unmarked show "about" 250 ohms ( 220-270)
Those with white dots show 350 ohms.
Sizes are 6.7mm dia with white dot.
Without dot they are 5.75 to 5.8 mm dia.
Any clues ?

with thanks in advance
Joe

[FrankB]

They look like old style VDR's Voltage Dependent Resistors, or possibly thermistors. Several brands of TV sets used them here, like Zenith & RCA.

[Silicon]

It might be an STC thermistor type CZ9A. These were marketed as Brimistors.

It has a resistance of 350 Ohms at 20 degrees C and 800 Ohms at Zero degrees.

The length is 3/4" and diameter is 5/16".

It can be used on the primary of mains transformers to limit 'switch-on surge'.
Get the application notes because it can be damaged if the peak current is too high.

They are designed to get hot in normal use.

[turretslug]

If it looks like a thermistor and acts like a thermistor.... I'd not seen (as far as I recall, anyway) crimped cap ones like that before, perhaps they were made by a cartridge fuse maker. If they could be budgeted for, radios/TVs with series heater strings sometimes had them to ease the brutal initial hit as they were switched on. The silvery metallized end connection types I'm accustomed to seeing in Blighty presumably use some sort of high-melting point solder for the joint, perhaps silver-loaded (or some cheaper but nastier metal that they could get away with using way back when).

I keep various types of all sorts of cold resistance in stock for when overhauling old stuff, typically something like rectifier cathode to reservoir connection- I take the view that the valves still around are "elderly survivors" and deserve a bit of respect and a gentle start. Also employed are modern inrush limiters of the primary-side, continuous-duty genre intended for SMPSUs, motors and the like- many commonly available ones are typically of 2-25 ohms, the pictured Epcos and Ametherm types are somewhat higher resistance than most at 220 0hms cold, i.e. significant when used with valve radios of a few dozen watts. Of course, it may be all hocus-pocus and wishful thinking, but seeing dial lamps come up slowly is re-assuring and some switches supposedly have marginal contacts. Not to mention that UK mains is frequently "generous" wrt spec., so the loss of 5-7 primary-side volts is no harm.

Maybe teaching to suck eggs, but a bit of maths and checking of characteristic curves shows that they tend to settle at around 120-160 degrees C in use, so care in positioning- but no worse than a small power valve in that respect.

[joebog1]

A second question.
I have a few of these "valves". Any idea what they are?
Its a glass plug that looks a little like an eye dropper.
It is filled with bright white crystals, the grain of which is about the size of table salt.

Joe

[AC/HL]

Source for testing Geiger tubes?

[turretslug]

Wow, Joe, you like to keep us scratching our heads!

http://www.tubecollector.org/cv2157.htm

[joebog1]

Thanks turret

I dont want you fellas gettin lazy

Seriously though I havent been able to find anything on them.
I have "stolen" your link though. Ive never seen that site before !!!

I have some more "odd ball" stuff that I will post as I go, apart from educating myself, it helps some of the others here too.
Thanks all
Joe

[Mr Moose]

Hello,
A bit more information here http://www.radiomuseum.org/tubes/tube_cv21157.html (I think the TR switch referred to is the Transmit-Receive switch which switches the radar aerial between transmitter and receiver.)
Yours, Richard

[joebog1]

Thanks Mr Moose,
I know about the radio museum, but they want money,
so I have never used the site, even though they have some stuff I want.
hhmm I hope I havent offended anyone !

I have been an active member of the open source society for almost 40 years!!!
Education, and help is free as far as Im concerned.
Having said that I WILL pay for a CD of collected circuits such as this site sells.
Its cheap for what you get!! and somebody had to assemble and scan alla that stuff.
THEN copy it all onto a CD, print a flash cover, etc etc.

Joe

[joebog1]

The last couple for this year ( I think )
2 transformers in the pic. Made by Alladin
part number is :
01-550
43A110171P1

on the reverse side of the can is:
6633D ( probably a date code)


AND some more thermistors. The label says thermistors, but once again I cannot find anything about them.

With thanks in advance for your patience

Joe

[turretslug]

Are the two holes in the thermistor end plate threaded?- I wonder if they were intended to secure it to a surface for sensing. Alternatively, could the short screw be an assembly supply thing, and they were intended to be assembled onto a longer 2 or 3BA etc. stud at the end of a dropper resistor or metal rectifier for inrush limiting (NTC) or protection/sensing (PTC)?

[G6Tanuki]

I've seen thermistors of that type bolted to large industrial (think thousand-amp thyristors in arc-welding and induction-furnace/heat-treatment gear) heatsinks for remote temperature-monitoring and (if necessary) automated shutdown.

The transformers look as if they are HF pulse=transformers of some kind. Old magnetic-core computer memory drivers used to be full of this kind of thing.

[Hartley118]

Originally Posted by Mr Moose

A bit more information here http://www.radiomuseum.org/tubes/tube_cv21157.html (I think the TR switch referred to is the Transmit-Receive switch which switches the radar aerial between transmitter and receiver.)

Pretty close......The TR cell is a gas discharge tube (usually argon) which short circuits the input to the radar receiver just as the magnetron fires its high power pulse. Imagine an inverted 'tee' made of waveguide with the vertical part feeding the radar aerial. The magnetron feeds its transmit pulse train into one horizontal arm of the tee, and the receiver sits on the other arm, with a protective TR cell in front of it.

When the magnetron fires its microwave pulse, the TR cell fires, its conductive plasma effectively short circuiting the receiver arm and encouraging those tens of kilowatts of microwave power to ascend to the aerial. Once a pulse is over, the ionisation in the TR cell dies away, opening the input to the receiver. There can be a beneficial effect in the relatively slow de-ionisation, which briefly delays full receiver gain for the early high amplitude returns from close-in targets.

Without the TR cell, the receiver front end would immediately become silicon vapour! In fact, the TR cell must be one of the most hard-worked components in radio transmission. Today the gas tube TR cell has mainly been superseded by semiconductor diodes. I do, however, owe some of my grey hairs to the inability of early solid state devices to work as reliably as the old gas discharge TR cell!

Martin

[joebog1]

To turretslug, yes the holes are threaded, and I did figure that they were designed to be bolted down. BUT, to what I have no idea. The last two items( transformer and thermistors) Are from a Snowy Mountains Authority auction 35 years ago when the last of the construction side shut down ( where I got my Kyoritsu VTVM and AVO 8 for $2.00)
I still have bags of parts from those auctions but the part numbers on the components, and the tags on the bags mean nothing on the net, in any of my data books ( and I have loads of them) or any tech people that I know. I have asked a few "oldies" that worked on the Snowy, but alas they have forgotten. And alas, there are only a few of them left.
Thanks to all
Joe