Care of Rare Valves

[Herald1360]

Maybe the dodgy nature of the valves is actually the reason they're still NOS? Someone just couldn't be bothered to throw them out?

[turretslug]

I wouldn't be surprised if at least some of the skewed/offset looking innards found in older valves without the mica bracing etc. were due to impact/dropping- the "right" sort of impact might not break the envelope but result in supports being noticeably bent. Every now and then, there's a tale here of an unfortunate 'scope that's been subjected to courier GBH and produces a peculiar trace as a result with long and precisely aligned electrode assembly being distorted, but without envelope damage.

[Station X]

The discussions regarding "flowing" glass are interesting, but can anyone answer the OP's questions in post #19 concerning valve storage?

[MotorBikeLes]

Does glass continue to flow at room temperatures? It will certainly depend on the glass's formulation. I have done or overseen many hundreds of tests of thermal expansion of glasses. Ceramic glazes to be more specific. Back then, they were all lead glazes (glasses), and by varying the composition, significant changes could be seen. Generally a "softer" glass, typically higher sodium content, would have a higher thermal expansion and a lower softening temperature. Above 500 to 600 Celsius, the glass was obviously mobile, but on cooling from the higher temperature, a marked kink in the graph defined the "softening point" which we regarded as "no longer liquid". Our interest was to compare the difference of size on cooling below the softening point with that of the underlying ceramic body.
However if you move from lead glasses to the more common window glass, you were more a simple mix of sodium compounds and silicon dioxide (eg sand). Whilst I have not tested any window glasses, I know they have much lower softening points, are cheaper to formulate, and require lower kiln temperatures. If you move just a bit further, you have various sodium silicates which most will know as "water glass". Some with high sodium content (I have a jar full here) are so viscous that it is difficult to get any from the jar when required.
I have absolutely no doubt that a thin, high sodium glass is capable of slow viscous movement at room temperature.
Les

[Argus25]

Originally Posted by RF Burn

Are they all Cunningham tubes? Considering the relationship between RCA and E. T. Cunningham could it be that RCA selected the 'imperfect' examples of their production for supply to Cunningham? Just a thought!

This particular one is Cunninghan. Most RCA 201A's and similar types are hard to see into. Oddly though, the Ken-Rad brand, at least most of the examples I have, have only a small getter and the electrode structures are readily seen.

[Argus25]

Originally Posted by turretslug

I wouldn't be surprised if at least some of the skewed/offset looking innards found in older valves without the mica bracing etc. were due to impact/dropping.

I have seen gun & insulator breakages inside CRT's that have been dropped, but in this valve the misalignment is largely due to the angle of the wide glass stem where it is fused with the bulb in the base area, rather than bent metal parts.

[philthespark]

I spoke to a chap this afternoon, he'd used a lot of pretty big valves in his job years ago. I mentioned this thread to him and he'd seen this phenomenon at work, they did a few tests and came to the conclusion that valves can and indeed do become damaged from being stored on their sides.
He reckons it's to do with the fact that they are normally used in the vertical position, and are designed as such, therefore there will be stresses and strains set up when stored in any other position.
Thinking about it it makes sense, any metal will distort over time and distortion will have an effect. in simple terms think of it like this.
If you stand a length of 4mm steel rod vertically and clamp both ends so it cannot move, it will remain straight. now turn it horizontally and after a period of time, days, weeks, months, you will notice that the rod develops a bend in the middle.
This is probably what happens with valves, it's irreversible and then you have a damaged valve. I seem to remember them being packed vertically, say a dozen individually packaged units in a bigger box, but don't recall any storage warnings. Today you see lots of items having storage instructions on the box, quite often you see the warning "store in an upright position" or "store vertically".
Maybe this fact was just one of those things that was obvious to the radio men of yesterday. a bit like we were brought up to know that hot coffee can scald you. today every coffee cup from fast food outlets has "warning contents may scald" written on it.
Mind you I'd rather admit to needing someone tell me a valve should be stored vertically, than admit I needed someone to tell me a hot drink could scald.

[peter_scott]

Originally Posted by Station X

Is the effect reversible? Could you positon the valve so that gravity tends to pull the electrode back to the correct position and see what happens?

It would be a very long experiment of course!

Or perhaps centrifuge it in a shorter time?

Peter

[Argus25]

Originally Posted by peter_scott

Or perhaps centrifuge it in a shorter time?
Peter

Actually that is a very clever idea with a high velocity small diameter centrifuge with the tube upright in it, to get it up to about 8 g's for 10 years to simulate 80g.years lying on its side.

[David Simpson]

STILL OFF TOPIC
All this talk of the structural & molecular properties of glass & the metal supports in valves - is "dooin me ed in", folks.
Now that there seems to be a consensus of agreement that valves should be stored vertically - can we get back to discussing appropriate methods of the protection & storage of rare &/or valuable valves. Or maybe all valves. Also, someone told me that just the colourful boxes from yesteryear are becoming valuable in their own right. MO, Mullard, Mazda, etc.
I've made a start with my collection storage-wise. What are other folk doing with their valves ?

Regards, David

[fetteler]

Got my good 'uns in a corrugated cardboard box all upright. The others are in a couple of old fashioned sweet jars just any old how. Nothing to SHOUT about

Cheers,
Steve.

[Bazz4CQJ]

Originally Posted by David Simpson

STILL OFF TOPIC
All this talk of the structural & molecular properties of glass & the metal supports in valves - is "dooin me ed in", folk David

David, do you think that anyone has any data, any evidence of any kind that proves there is any optimal way to store a valve? As I said previously, there's 15psi of atmospheric pressure on the envelope pushing it inwards, and has been since the day it was made. In a household environment, I don't there is a big issue on storage, with the possible exception of using any packaging which could adhere to and pull off the labelling.

B

[Herald1360]

Rats! The partitioned shelf I just put up to hold loads of boxed valves on their sides doesn't seem such a good idea now- especially since it's only a foot above a radiator. Back in the drawers with 'em!

[Boater Sam]

SORRY, David, I led it up a muddy creek.
In answer to you question, all new valves that are considered worth it are in their boxes, stored vertically in ally flight cases.
All used and tested non miniature valves are in open plastic mushroom trays with a bit of corrugated cardboard between them.
The bulk of the miniature pulls are vertical in open trays which are full to stop them rattling about.
The whole lot are on steel racking, about 50m of it!
I did think that I could find anything until I recently wanted an EF80. I have a tin trunk with a few hundred just dropped in, I can't get precious about them. Now I can't find the trunk! Its been slid behind something else and hidden.
I do have another big plastic box with all the new P series and eht rectifiers etc which will get chucked out when I next run out of rack space. I don't do TVs anymore.
The used TV stuff is in a plastic dust bin!

[kalee20]

Glass doesn't flow at room temperature, it's an amorphous solid.

What happens as it's cooled, is that viscosity rises as temperature drops, and at a particular temperature viscosity heads to infinity. Below that in temperature, no flow takes place.

So, valves don't collapse; lenses and mirrors don't go out of focus. Wine glasses ring like a bell (try that with a bell made of lead and you are up for a disappointment unless you cool it with LN2 first!).

[Argus25]

Originally Posted by kalee20

Glass doesn't flow at room temperature, it's an amorphous solid.

Quite right, I noted it was an amorphous solid in post 7.

Some valve specs include operating positions for the valves, presumably this is related to possible deformation of the metal parts of the valve with heating and nothing to do with the glass.

[Boater Sam]

If care would include shipping then careful packing is vital. I send small valves in polystyrene packing in cardboard boxes with stiff card insets to prevent crushing.
The larger ones I send in tin cans, a worthwhile recycling use, with bubble pack wrapping,and a cardboard box to stick the labels onto.
Modern tins are so thin that they hardly add to the weight at all.
I try to avoid the postal service, its expensive and I have had losses before. I find carriers such as Hermes, UPS, to be very reliable and careful if the item is well labeled as fragile. But they would probably not pay out on the insurance for valves, they exclude glass items.

[kalee20]

Originally Posted by Argus25

Quite right, I noted it was an amorphous solid in post 7.

You did indeed - remiss of me not to have acknowledged that!

Originally Posted by Argus25

Some valve specs include operating positions for the valves, presumably this is related to possible deformation of the metal parts of the valve with heating and nothing to do with the glass.

I think that's right - even reversible sag of grid wires as things get hot and expand.

I have seen caveats against base-up operation of high-power valves like KT88 unless fan cooling is employed, because airflow is impeded more by a chassis above than a chassis below.

Regarding misalignment of electrode structure, I'd find it difficult to accept that this was by mechanical shock! My experience of a dropped valve is that bits break off the glass pinch due to jarring. I've never thrown one around to see if I can get the metal wires to bend. (Button-based valves are more robust, they're OK till the envelope breaks). So I reckon that misaligned valves left the factory like that - but presumably still met test specifications (which may have been relaxed enough to allow slightly misaligned valves to pass).

[PJL]

Bending could be from manufacturing defects when the pinch is made, failure of welds, warping/relaxation due to heat or being dropped. Heating and slow cooling would soften many metals.