Is Shed Storage Detrimental To Valves?

[Sinewave]

Almost certainly the main issue with shed storage, if it's typically cold and damp, can be tarnishing of any contacts/switches in the entire set. Possibly moisture intake from paper caps etc.

[Philips210]

Hi.

Over a decade ago I put a 6F23 valve out in the garden to see how the pins corroded. I was quite surprised to see hardly any tarnishing of the pins despite the valve being out in the open for around 10 years.

Also, back in the mid 1990s I bought a large box of valves at our local boot sale. The box was the type TV service engineers carried in their vehicles. It had many dividers so generally protected the valves quite well. What did surprise me was that some of the valves had a severe amount of green corrosion on the pins. I thought that it must have been something more significant than just high humidity to cause that level of corrosion. Maybe the valves were stored with something likely to cause corrosion?
I read somewhere that some Mullard Kradlepak valve boxes which contain a blow moulded plastic tray can be responsible. Outgassing from the plastic perhaps?

OT, but most sheds have tanalised timber in their construction and I read that ordinary zinc plated nails/screws will readily corrode in contact with the wood. I assume this would only apply to the fastenings holding the sections/cladding together as opposed to surface contact of stored items.

Regards,
Symon

[high_vacuum_house]

I would think the valve out in the open would survive that environment better as it would have plenty of airflow around it and therefore dry pretty quickly. It would also get wet with nothing much chemically stronger than rainwater. A valve in a valve box wrapped in paper would tend to keep the damp in and also be affected by other chemicals out gassing from the paper and cardboard as well as other chemicals (paint, creosote, cleaners ECT.) in its vicinity in which it is kept.

B9a and B7g valves tend to be worse than any other valve for randomly cracking the glass base across one or more pins even with no apparent bending of the pins. Possibly as a result of stresses being left in the glass during production. A quick hot/cold change is then enough to allow the crack to start.

I haven’t got that many older octal valves with a pinch seal but would believe that these would survive better having more glass to run the lead out wires from.

Christopher Capener

[factory]

All the later valves & readout tubes with a glass base can suffer from rusting/corrosion of the pins, which can then crack the glass seal, even equipment that looks clean & corrosion free can be affected, such as these two readout tubes which suffered this way.


Having said that equipment with signs of poor storage* & heavily corrosion equipment has a higher chance of pin corrosion & valve failure as a result.

I've noticed some older Burroughs readout tubes are better protected with extra sealing material around the pins.

Miniature neon lamps can suffer in the same way as the leads are copper plated iron/steel? They can drop off circuit boards as well as crack.

*Trouble is most old equipment seems to have been stored badly at some point over the years.

Edit: Could dissimilar metal corrosion between the pins & the socket contacts also be a problem?

David

[paulsherwin]

Some pins seem much more vulnerable to corrosion than others.

[Fidelity Fan]

Originally Posted by Sideband

So if the PCL86 has a 13.3V heater and the ECL86 has a 6.3V heater, how did the PCL86 light up with only 6.3V? Surely it wouldn't have worked and even if the heater did give the faintest of glows, it couldn't possibly have worked anywhere near efficiently.

I suspect you have other problems......

I have checked over what I tried. The PCL86 lights up very faintly. I tried removing the PCL86 and powered up the amp with only the other ECL86 installed. There was no sound at all, so it shows that the PCL86 must be working to get sound, albeit not very efficiently as you said.

I have since tried the ECL86 that I believed to be faulty in my Hacker Gondolier GP42. I got the same distorted sound whichever other ECL86, I tried pairing it with. I had already cleaned the pins of the valve with some fine sandpaper.

[Sideband]

There should be sound with one ECL86 as already stated. It won't be loud but it should be OK. Still think there is another problem. Try the ECL86 in the other socket. Does one socket give sound and the other doesn't?

[PJL]

It's not wise to use an output valve that is thought to be faulty as it could damage other components like the output or mains transformers.

Running a push-pull amplifier with only one output valve carries the same risk as common cathode bias will cause the remaining valve to thermally runaway. The GP42 has separate cathode bias but the HT voltage will rise and this might also cause a problem.

Some voltage measurements of the anode, cathode and grid of both the triode and pentode of both valves will help us determine the fault condition.

[Sideband]

Originally Posted by PJL

Running a push-pull amplifier with only one output valve carries the same risk as common cathode bias will cause the remaining valve to thermally runaway. The GP42 has separate cathode bias but the HT voltage will rise and this might also cause a problem.

Yes....should have added that this should only be a quick test. Don't leave it running with only one valve.

Originally Posted by PJL

Some voltage measurements of the anode, cathode and grid of both the triode and pentode of both valves will help us determine the fault condition.

That is the best advice. List the voltages around the output valves.

[woodchips]

Some other points.

Valve pins are carefully made so heating and cooling don't stress the glass and crack it. At the moment I can't find exactly what metal is used, but not iron, lower thermal expansion?

In the good old days, before central heating, my dad used to store valves in the timber shed, never a problem. This must have lasted from the 50's until 2008 when he died.

Do not, under any circumstances, store anything in a steel container! They have no ventilation and sweat like crazy. Understandable really since the container has to be near water proof whilst being shipped and the only vent holes are tiny little ones only used for pressure equalisation.

I have found that the metal sheds, Youngmans, are really very good for storing because they have lots of ventilation, never had problems with condensation.

Timber sheds are also good, but must have large vent holes, 3" or so.

If store in the loft then make sure there is a good draft through the eaves.

I wonder if it is air movement that keeps them good, not had valves going white after decades of storage.

[David Simpson]

Some years ago I acquired a heap of valves from a University storeroom - they were in mint condition, even the beautiful coloured boxes from the 20's & 30's. A couple of years back I was given large amount of "silent key" valves, which had obviously been stored in a damp loft or shed - the amount of "Mank" was horrendous as was the pin corrosion. Also, many turned out to be useless "pulls".

Regards, David

[factory]

Originally Posted by woodchips

Some other points.

Valve pins are carefully made so heating and cooling don't stress the glass and crack it. At the moment I can't find exactly what metal is used, but not iron, lower thermal expansion?
snip...

They only used a very small amount of the expensive material in the glass base, the pin & internal connections are both made of cheaper materials where closer thermal expansion properties aren't needed. Here is a random expired valve showing the different materials going through the glass base.


I wonder if they did further cost cutting, as some later ones go rusty, but older ones have green corrosion instead.

David

[woodchips]

According to Materials and Techniques for Electron Tubes by Kohl, it isn't straightforward.

There are different grades of glass, hard or soft. Softer glass is used on things like CRTs, harder glass on things like power valves.

Softer glasses have to be pumped out at much lower temperatures.

Softer glasses use lead in wires made from copper clad iron-nickel alloy known as Dumet.

Harder glasses use lead in wires made from tungsten.

Harder glass are more expensive it would seem.

It is pointed out that the tube is no stronger than its weakest link, voltage breakdown, corrosion resistance, contact resistance etc.

European valve manufactures made a good job, the fact that 99.999% plus of my valves are still high vacuum after decades rather suggests this.

But, things like Nixie tubes could well be made to lower standards, as David points out, and in the commercial competition could have been at a reduced standard? The photo in post 32 looks good to me? But, for anything that was intended to be used the best material was used? Just look at the quality of the cathode coatings used in the 50's and 60's, vastly better than the stuff used now when it spits and pops.

[Fidelity Fan]

Originally Posted by Sideband

There should be sound with one ECL86 as already stated. It won't be loud but it should be OK. Still think there is another problem. Try the ECL86 in the other socket. Does one socket give sound and the other doesn't?

Thanks for your post. I have found that when trying out a good ECL86 that there was no sound when the ECL86 is plugged into the socket next to the EZ80 and sound when fitted to the socket furthest way.

I have now tried the AL42 unit with two PCL86s. The unit works. As ECL86s are very expensive now, I think I am going to go down this route and use a 13 - 14v mains transformer to supply the PCL86 heaters. Another member on here recently started a thread about the same idea, but I haven't been able to find it again.

As the AL42 looks like it has been stored in damp conditions, I will give it a service replacing the grid coupling capacitors, C6 and C7, (0.05uF), R6 and R7 (220k 0.5w), (which can cause distorted output if they go high in value), all the electrolytic capacitors and any other resistors that are out of tolerance.

[turretslug]

If you value a collection of valves (and if not, then why are you collecting them?...) at least invest a few pennies and a few seconds per valve in putting each in a "gripseal" polybag. These can be bought in 100s or even 1,000s, a while back I bought 1,000 of a size that accomodates typical B7g/B9a signal valves for about £7, I probably have about 800 left! This will at least greatly slow the rate at which moisture and consequent corrosion affects them, another advantage is that it reduces the impact of glass-to-glass clash in a bulk box. Anything of any significant value (6V6 upwards) deserves further cosseting in something like a plastic sandwich box with a clip-over lid, several middling-size bottles can be accomodated in a typical box. If this sounds like too much trouble/time/space, re-appraise why they're being kept!

[Fidelity Fan]

Originally Posted by turretslug

If you value a collection of valves (and if not, then why are you collecting them?...) at least invest a few pennies and a few seconds per valve in putting each in a "gripseal" polybag. These can be bought in 100s or even 1,000s, a while back I bought 1,000 of a size that accomodates typical B7g/B9a signal valves for about £7, I probably have about 800 left! This will at least greatly slow the rate at which moisture and consequent corrosion affects them, another advantage is that it reduces the impact of glass-to-glass clash in a bulk box. Anything of any significant value (6V6 upwards) deserves further cosseting in something like a plastic sandwich box with a clip-over lid, several middling-size bottles can be accomodated in a typical box. If this sounds like too much trouble/time/space, re-appraise why they're being kept!

I was given the valves back in the early 1980s by a good old friend who had a radio repair shop. I was about 13 at the time and collected and repaired old record players. I have recently got a new shed and found on emptying the old one that there are other items that I don't need that may be of use to others, including a few VHS recorder cassette housings.

[factory]

Originally Posted by woodchips

According to Materials and Techniques for Electron Tubes by Kohl, it isn't straightforward.

There are different grades of glass, hard or soft. Softer glass is used on things like CRTs, harder glass on things like power valves.

Softer glasses have to be pumped out at much lower temperatures.

Softer glasses use lead in wires made from copper clad iron-nickel alloy known as Dumet.

Harder glasses use lead in wires made from tungsten.

Harder glass are more expensive it would seem.

It is pointed out that the tube is no stronger than its weakest link, voltage breakdown, corrosion resistance, contact resistance etc.

European valve manufactures made a good job, the fact that 99.999% plus of my valves are still high vacuum after decades rather suggests this.

But, things like Nixie tubes could well be made to lower standards, as David points out, and in the commercial competition could have been at a reduced standard? The photo in post 32 looks good to me? But, for anything that was intended to be used the best material was used? Just look at the quality of the cathode coatings used in the 50's and 60's, vastly better than the stuff used now when it spits and pops.

The picture from post #32, yes it's hard to see why that one failed, it had gone white and disintegrated further on removal. But others that had gone white were intact had a little green corrosion around some pins were they meet the glass.


Looking closer at a pin removed from that valve it's clear to see the different parts used, all seem to be magnetic.


The machine they are from has quite a bit of corrosion on the casing, the CRT worries me too as the side connections have rusted, hopefully it'll be OK as it's not an easy to obtain one.


David

[factory]

The older Burroughs readout tubes were definitely better made, here is a faulty one from 1963 (the 6 is O/C but still usable for test gear that only needs lower numbers), I hope it's clear to see the dark green coating where the pin passes through the glass, this must help prevent corrosion getting near the seal.


And the later Burroughs tube from 1966 with rusty pins, as it is completely dead I removed a pin, this appears to be made from one material only.


The replacements were very hard to find as it needed the decimal point, which ruled out all the cheap tubes & Russian types.

The fact readout tubes have far more pins than a normal valve and they are often very closely spaced may help contribute to increased seal failures.

David

[Rileyman]

Originally Posted by JonSnell

The only problem storing valves in a shed or workshop is the discolouration of the pins. No other problems can, in my experience, occur.
Temperature does not affect them nor does air pressure/moisture etc.
Any distortion is probably due to either external components, bias setting or maybe the valve was faulty before storage.
I have valves that I stored from the 1960s and never had an issue. Number 83, mercury vapour rectifiers can condense their mercury within the glass but that soon restores after a few minutes of use.
There are so called HiFi experts that freeze valves before sale, adding 'cryogenicly sorted' to their sales blurb and some people actually pay over the top for them!
A fool and his money, is easily parted.

I assume that your M.V. rectifiers are type 83V not 83 , and can you confirm that the "few minutes of use" are with no H.T. applied ?
It worries me that someone out there could be unaware of this requirement.
One of my Bench Power Supplies is fitted with a (nominally) 1 minute B7G-type Thermal Delay Switch , to allow the NGT5s to clear the "fog" which forms on the glass on switching-on the heaters .

Laurie

[Bazz4CQJ]

One type of valve that does not cope with bad storage is the Acorn series. Because of the unusual way the valve was manufactured, the 5 "waistband" pins are made of an alloy (iron/copper?) that corrodes badly (becomes covered in a black oxide), and the corrosion continues between the glass/metal seal and the vacuum leaks away. I think that such corrosion may even have got started as they were shipped in the cold, dank holds of the Liberty ships as they sailed the North Atlantic.

B