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Old 31st Jul 2022, 10:56 pm   #1
AdrianH
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Default Ion burn, When did aluminised CRT's start and become the norm?

This thinking about this and thought I would throw it out to the wider knowledge base.

The 1948 Pye set I have (duff tube) is a straight gun CRT that would suffer from ion burn, I have seen an advert for a 1951 TV with aluminised CRT, so assume that would be a straight gun, my 1954 Fergy has an ion magnet to bend the beam so Ion burn is not an issue.

So just wondering when aluminised CRT's were first done and when they became the norm?

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Old 1st Aug 2022, 8:12 am   #2
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

EMI [TA10/15]and Cossor were early makers of aluminised tubes, that would be around 1949. Mazda soon followed with the 15" CRM151 1950 and the CRM123 approximately 1952/3. Mazda aluminised every tube since that date.

Mullard were late, the first domestic aluminised TV tubes were the very rare 12" MW31-23 used in the PYE LV21C in 1950. There was then a five year gap until the 21" MW53-20 and the AW36-20 were introduced in 1955. Mullard preferred the ion trap maybe due to patent costs. They did produce a range of early monitor tubes that were aluminised. Aluminising did away for the need of an ion trap but many makers continued to use one.
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Old 1st Aug 2022, 8:25 am   #3
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

I always thought the main reason (in the early days) for aluminised CRT was to give you a brighter picture with more of the light produced by the phosphor going toward the viewer.

I suspect that the heavy ION's would still damage the screen in time.

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Old 1st Aug 2022, 9:27 am   #4
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

A Brimar advert:

https://worldradiohistory.com/UK/Wir...ed%20screen%22

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Old 1st Aug 2022, 10:20 am   #5
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

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Originally Posted by Heatercathodeshort View Post
Aluminising did away for the need of an ion trap but many makers continued to use one.
John.
Sixty-plus years later, RACS in France were to add aluminising to several of the ion trap CRM121's they rebuilt, making them into (sort of) CRM123's! These performed well at EHTs as low as 7kV. The theory being that despite the light gain provided by the forward reflection, you needed a certain minimum of EHT to 'punch through' the aluminium coating.

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Old 1st Aug 2022, 10:28 am   #6
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

Quote:
Originally Posted by ms660 View Post
A Brimar advert:
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July 1955 issue of WW. Pg 55
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Old 1st Aug 2022, 10:42 am   #7
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

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A Brimar advert:

Lawrence.
From the same link an Ediswan advert.
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Old 1st Aug 2022, 10:49 am   #8
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

I have never seen an ion burn on an aluminised tube. Screen burn yes caused by line or frame collapse or no scan at all! generally you needed a minimum of 7kv to get the advantage of an aluminised tube but EMI managed to do it at 5kv with the 3/16 employed in the 1807 that gave a good picture when working..
Yes Brimar marketed the aluminised C12B in 1949 made by Cintel. A very good triode tube that is capable of giving a super bright picture at the recommended 10kv EHT. Used in the PYE V54C and the KB EV30 series. John.
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Old 1st Aug 2022, 10:57 am   #9
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

Aren't there two types of aluminising? One being the phosphor itself, eliminating the ion trap, and the other being the rear of the glass bulb (on the inside of course) having an aluminium coat to improve contrast/brightness.

I have a tv with the Philips MW53-20 and here the rear of the bulb is aluminised, making it capable of giving a very bright picture. The gun is still slanted though, and an ion trap is of course needed.

I have tv's with both the 17" MW43-64 (non back coated) and the MW43-69 which has aluminium coated bulb. Both have slanted guns and needs ion traps.

Around 1959/60 where 110 degress valves were introduced here, there were no longer need of an ion trap, hence aluminised phosphor coating.

I have seen 70 and 90 degrees replacement valves for earlier sets, still with the same type number except having a Z added. See attached photo. A sticker says no ion trap, which the original valve had. I replaced this valve in a set, and it was obvious that the gun was straight, compared to the worn out valve. Both had aluminised bulb, but the new one didn't need an ion trap anymore.

So I believe there is a bit of confusion about aluminised picture valves, since it can both be related to the phosphor coating and the mirror like coating on the inside of the bulb.

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Old 1st Aug 2022, 11:16 am   #10
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

The Z gun was in fact the later gun from the 110 degree tubes with the B8A base. It was used to replace the obsolete gun in mainly Mullard tubes such as the MW43-64/69, AW43-80 etc and late production replacement new tubes,
It was supplied with a small mod sheet. I don't think it was the type of phosphor that had anything to do with ion burn proofing. I think manufacturers liked the idea of an 'ion trap' in the sales literature as the public were very aware of problems with their first generation TV receivers screen becoming stained, even if it was not needed in aluminised tubes. J.
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Old 1st Aug 2022, 11:23 am   #11
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

I have to admit that the idea of aluminising being actually part of the phosphor is a new one to me.

One thing I learned when visiting RACS was that there is also such a thing as 'fake ion burn'. This is a large patch of yellowing within the front glass (as distinct to a burn of the phosphor) that can appear after long use. It's generally pretty mild - I had to have my attention called to it to notice it at all. Nothing can be done about it.

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Old 1st Aug 2022, 12:02 pm   #12
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

Quote:
Originally Posted by ms660 View Post
The search doesn't work for me.

https://worldradiohistory.com/UK/Wir...R.pdf#page=129

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Old 1st Aug 2022, 12:07 pm   #13
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

Quote:
Originally Posted by peter_scott View Post
Quote:
Originally Posted by ms660 View Post
The search doesn't work for me.

https://worldradiohistory.com/UK/Wir...R.pdf#page=129

Peter
It works for me (screen shot)

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Old 1st Aug 2022, 12:09 pm   #14
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

Wow lots of information, I did believe that the aluminised backing to the phosphor had two advantages, lack of ion burn and brighter picture, but as mentioned in the thread needed a higher EHT, it is all interesting. Looks like patents came into it and perceived customer expectations for keeping the ion trap.

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Old 1st Aug 2022, 12:39 pm   #15
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

If it was thought that an ion trap wasn't needed then they probably wouldn't have fitted one.

Lawrence.
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Old 1st Aug 2022, 3:36 pm   #16
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

Quote:
Originally Posted by ms660 View Post
If it was thought that an ion trap wasn't needed then they probably wouldn't have fitted one.

Lawrence.
No "probebly" about it.

Tubes that required an ion-trap magnet had an electron gun that without the magnet, was aimed at the flange rather than the faceplate.
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Old 1st Aug 2022, 3:48 pm   #17
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

In post 10
Quote:
Originally Posted by Heatercathodeshort View Post
The Z gun was in fact the later gun from the 110 degree tubes with the B8A base. It was used to replace the obsolete gun in mainly Mullard tubes such as the MW43-64/69, AW43-80 etc and late production replacement new tubes,
It was supplied with a small mod sheet. I don't think it was the type of phosphor that had anything to do with ion burn proofing. I think manufacturers liked the idea of an 'ion trap' in the sales literature as the public were very aware of problems with their first generation TV receivers screen becoming stained, even if it was not needed in aluminised tubes. J.

So this suggests a reason why some aluminised tube may still have an ion trap. I wonder if there is also a case of using up older assemblies in tubes that had the aluminised back coating on the phosphor.

It was this coating as far as I understood that stopped the requirement for the Ion trap, I am sure I have read this as such somewhere. Is this correct?

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Old 1st Aug 2022, 4:04 pm   #18
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

Quote:
Originally Posted by rambo1152 View Post
Quote:
Originally Posted by ms660 View Post
If it was thought that an ion trap wasn't needed then they probably wouldn't have fitted one.

Lawrence.
No "probebly" about it.

Tubes that required an ion-trap magnet had an electron gun that without the magnet, was aimed at the flange rather than the faceplate.

QUOTE=rambo1152;1489037]
Quote:
Originally Posted by ms660 View Post
If it was thought that an ion trap wasn't needed then they probably wouldn't have fitted one.

Lawrence.
No "probebly" about it.

Tubes that required an ion-trap magnet had an electron gun that without the magnet, was aimed at the flange rather than the faceplate.[/QUOTE]

My previous post was in reference to ion traps that were fitted when the CRT was aluminised, some examples in here:

http://www.r-type.org/articles/art-004e.htm#025

Lawrence.
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Old 1st Aug 2022, 9:26 pm   #19
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

Is it possible that they used the aluminising to brighten the picture and used a gun with an ion trap due to that being tried, tested and available. This would allow time to develop a suitable straight gun.
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Old 2nd Aug 2022, 7:11 am   #20
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Default Re: Ion burn, When did aluminised CRT's start and become the norm?

I think your spot on Frank. Mullard used basically the same ion trap gun for many years from around 1950 to 1958 aluminised or not. It was the introduction of the 110 degree AW43-88 in 1959 that finally did away with it.
I do not remember GEC or Ferranti ever using an ion trap magnet with their aluminised triode tubes. John.
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