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Old 20th May 2021, 8:24 pm   #21
AdrianH
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Default Re: Help with some old TV tubes.

Rich thanks for the information, i have downloaded a 29 Meg file from worldradiohistory site so that goes a long way to plug a few holes in my information held on the PC.


I am about to try and power the heater on the COSSOR tube, it may be to air, so I will do a quick emission test.

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Old 20th May 2021, 8:27 pm   #22
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Default Re: Help with some old TV tubes.

AdrianH wrote: "The next is a 14 inch tube very the same as the MW36-26 in dimensions, requires an ion trap magnet, has some printing in the screen band area that says made in Holland, The gun assembly is different to the MW36-24 and it has what I would describe as the standard later spring clip anode connection of a ring in the glass. Lastly a standard Duodecal 7 pins base."

The 14" CRT is the electrostatic focus AW36-21.

DFWB.
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Old 20th May 2021, 8:51 pm   #23
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Default Re: Help with some old TV tubes.

OK on the hunt for that data sheet and see if I can find some pictures while I leave the 17" on test.

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Old 20th May 2021, 9:57 pm   #24
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Default Re: Help with some old TV tubes.

Found some basic data and a picture from this site, so i have just taken a better pic of the gun on my tube
and have it with a picture from a Duke Nuken post about a duff AW36-21 and they do look very similar to each other, some differences which could just be down to year of manufacture.

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This is a new picture of the 17" tube, with the light coming in from the side i noticed some white shading where I would expect the getters to be, hence thinking it could be going to air.
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It is being fed with 6.3 Volts for the heaters and have 300V via a 300K resistor between g1 and Cathode to give a measure of cathode emission, it was very low to start with and is slowly building up with time. I appreciate this may not be an indication of vacuum as that will only be noticed with HT applied and watching for the blue glow, but the best i could do at the moment.

Thanks everyone for assistance it has help me quite a lot.

The tubes need work to the aquadag as a lot is flaking away I have some on order, A fibreglass small brush will be used to clean up the pins and a few bases need re-fixing, but I believe they will be useful in the future.

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Old 20th May 2021, 11:10 pm   #25
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Default Re: Help with some old TV tubes.

From the Mullard Maintenance Manual. Information about the AW36-21 CRT.

DFWB.
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Old 21st May 2021, 10:13 am   #26
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Default Re: Help with some old TV tubes.

Thanks FERNSEH for the image I have saved it.

The 17 inch had an intermittent contact on the heaters, the base was loose so I have removed that and cleaned up the next of the tube, still awaiting the fibre brush to clean the pins and then I will re-attach and solder it back up.

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Old 21st May 2021, 10:33 am   #27
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Default Re: Help with some old TV tubes.

Cossor 172K data.

Handling the book required extreme care as the paper is crumbling away while the print has faded badly in places.

A minor point but ILIFFE Radio Valve Data, omitted to show the a1 and a2 potentials and that pin 6 has an internal connection.

A piece of trivia, a price list dated 19th November 1956 and a new 172K is priced at 14 plus additional Purchase Tax of 6 2s 11d

Rich
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Old 21st May 2021, 10:47 am   #28
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Default Re: Help with some old TV tubes.

Thanks for that, picture is saved. As a note there is no pin 6 connection on this tube One guesses that it all depends on who made the tube. Unless they used ic as nc as well?

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Old 21st May 2021, 11:49 am   #29
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Default Re: Help with some old TV tubes.

The tube is a tetrode so it was not made by Mullard, more likely Electronic Tubes Ltd.
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Old 21st May 2021, 2:09 pm   #30
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Default Re: Help with some old TV tubes.

Tube base back on the 17 inch CRT and cooking again in the tester, after warm up last night it started at less than 0.2mA and slowly crept up to 0.8mA, when I tried again this afternoon after a warm up period it started again at around 0.6mA, the within a few minutes to 0.7 and now after approx 15 minutes it is at 0.8mA and a forward voltage drop of 54 Volts, which I think is what it went up to last night. So all in all I think it could be a useful tube.

The existing aquadag is crazed with gaps in it all over the glass, the existing coating will also be very dirty/dusty etc. So I am thinking of cleaning it all off the tubes, wiping down with acetone, masking and coating the outside areas of the tubes with a brush. Has anyone done this to their own CRTs and what sort of results did you get, I will not be able to dry them in an oven so just a warm room will be the best I can do.

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Old 21st May 2021, 3:45 pm   #31
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Default Re: Help with some old TV tubes.

Adrian,

That is perfectly feasible.
You can use some liquid aquadag or for example a spray can of Graphit 33.

I had some Graphit 33, but the propellant was gone over time.
I opened the can and used it as a liquid aquadag which I applied with a brush.
Or, perhaps, for this CRT I used some aquadag that I still had - can't remember.
It is not critical at all.

It is not required to remove all the old aquadag, just remove what is not attached to the glass anymore.
If you remove everything and use a spray can, of course you get the best optical result, but the working is the same as "patching up".

A CRT with almost all aquadag gone:
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I masked the neck and around the EHT connector with tape:
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And the final result (not a very clear photo due to the black surface):
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I let it dry at room temperature, which went fast enough.
Afterwards, just give it a wipe to remove the top which always gives off a bit.

If only a small part of the layer is bad, just remove the loose parts and it is still good enough.

Hope this helps.

Jac
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Old 21st May 2021, 4:34 pm   #32
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Default Re: Help with some old TV tubes.

Thanks Jac
These are a couple of pics of the condition
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They have been up in a house loft for years so the main concern was a coating ofgrim that would stop a new coat adhering to the existing, I can only guess that they have cycled from being damp to very warm in the loft space over years that has lead the condition they are in.

I watched a video last night from the early Television museum regarding re-gunning tubes and the guy just used a blade to scrape off the dag and then after plenty of washing when ready masked and applied with a brush, I did not know if room drying or oven drying was used after.

I am getting 4 bottles of this stuff https://www.betterequipped.co.uk/aquadag-100g-5707

It was cheap enough when compared to the P&P, I could probably dish out to others after.

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Old 21st May 2021, 4:48 pm   #33
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Default Re: Help with some old TV tubes.

Adrian,

That aquadag look fine to me. No information on resistance values though, but the actual resistance of the aquadag layer is not critical, as long as it has a fairly low value. Just test with a multimeter.

Basically aquadag is a colloidal solution of graphite in water, so drying in normal room temperature is fine. And you do not introduce stress in the glass this way.

For removal just use any procedure that works for you.
For the looser parts I use a knife (to scrape it off). It will dissolve somewhat in water, but not too good, so just using a wet cloth will not be the only way to get rid of it.
When all loose particles are removed, it is best to clean the glass with some IPA or other alcohol to ensure good adhesion.

It is all a lot easier than I describe.

Jac
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Old 21st May 2021, 6:07 pm   #34
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Default Re: Help with some old TV tubes.

Thanks for the information, I have a week or so before the stuff arrives so i will ask them for some information, I have some from another supplier, so will see what happens next. It gives me time to clean and mask off the tubes.

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Old 8th Jun 2021, 3:45 pm   #35
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Default Re: Help with some old TV tubes.

An update on this. The Aquadag arrived 4 or 5 days ago and I have just got around to trying it. I used a blade to first scrap off as much of the loose stuff as possible, thisshowed large areas where there were clear tracks all over the screen, so I went further and followed it up with water and a plastic scrub, finally with a wipe down with acetone getting back to the glass.

The neck, screen and anode areas masked off with tape I tried one of the bottles, gave it a rigorous shake and poured some out into a small jar to brush on. What a waste of money in my mind, it is extremely runny has no adhesion to the glass at all, it also had no smell and as I was expecting it to have some form of odour to it. So I suspect it is just a pure water suspension. I will leave what I have got on it for several days and may consider pouring out the other bottles into a larger jar and letting the water slowly evaporate and try again in a week or so time.

Perhaps it is me, I am expecting it to brush on like a paint after watching one of the Early Television Museum youtube videos?

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Old 8th Jun 2021, 4:04 pm   #36
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Default Re: Help with some old TV tubes.

Hi Adrian,
I've recoated tubes successfully with this:-
https://www.rapidonline.com/kontakt-...-200ml-87-0695

Cheers
Andy Beer
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Old 8th Jun 2021, 4:18 pm   #37
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Default Re: Help with some old TV tubes.

Thanks for the link Andy I will order some for early next week as I will be away from home for a few days, going down towards the South coast area, just had a negative test result checking all is OK before I head down tomorrow.

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Old 8th Jun 2021, 4:20 pm   #38
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Default Re: Help with some old TV tubes.

Quote:
Originally Posted by AdrianH View Post
An update on this. The Aquadag arrived 4 or 5 days ago and I have just got around to trying it. I used a blade to first scrap off as much of the loose stuff as possible, thisshowed large areas where there were clear tracks all over the screen, so I went further and followed it up with water and a plastic scrub, finally with a wipe down with acetone getting back to the glass.

The neck, screen and anode areas masked off with tape I tried one of the bottles, gave it a rigorous shake and poured some out into a small jar to brush on. What a waste of money in my mind, it is extremely runny has no adhesion to the glass at all, it also had no smell and as I was expecting it to have some form of odour to it. So I suspect it is just a pure water suspension. I will leave what I have got on it for several days and may consider pouring out the other bottles into a larger jar and letting the water slowly evaporate and try again in a week or so time.

Perhaps it is me, I am expecting it to brush on like a paint after watching one of the Early Television Museum youtube videos?

Adrian
As said earlier, it is supposed to be a colloidal solution in water, so no smell.
Make absolutely certain that you mix the fluid extremely well. It tends to settle towards the bottom of the bottle and clumps together. Give it a very, very good stir.
It usually is not as thick as paint, but it should also not be as runny as water.
I had good results with it in the past, but what I used was coming from a different source as yours.
As also indicated earlier, Graphit 33 spray also works well.

Success with the stirring and application!

Jac
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Old 8th Jun 2021, 4:47 pm   #39
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Default Re: Help with some old TV tubes.

Gold leaf is often applied to surfaces with a weak glue consisting of diluted PVA (50%).

Perhaps that might act as a binder for the aquadag.
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Old 8th Jun 2021, 6:38 pm   #40
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Default Re: Help with some old TV tubes.

Quote:
Originally Posted by Jac View Post
As said earlier, it is supposed to be a colloidal solution in water, so no smell.
...
Jac
The Wiki suggested some Tannic acids so thought there would be a bit of a smell? I can not find any mention of the concentration graphite to water so it could any dilution. I will let some water evaporate and give it another try and if all else fails get the aerosol.

OK on the PVA as a thought, but will see how I get on with the normal process first.

Adrian
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