Help with some old TV tubes.
 

I picked up a small quantity of CRTs earlier in the week (details on Golborne), and would like a bit of assistance trying to fathom a few of the tube types as they either have no label or unreadable labels to them.

The 1st is a 17 inch with a partial label on it COSSOR 17?K It has an external aquadag coating 34mm dia next and overall length approx 490mm

Now I have not found data sheets on Cossor CRT's and wonder if these are the same as the Mazda CRM172 so a pointer in the correct direction would be appreciated. I have a Murphy V280 which has a CRM171 CRT fitted and in case that is bad I am wondering if this would be OK to use, I notice the Mazda tubes are 12 Volt heaters, this one I have not powered up.
Attachment 234476
Attachment 234477
Attachment 234478

Adrian

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.
Attachment 234485
Attachment 234486

Re: Help with some old TV tubes.
 

The last tube I am asking about is a 12 inch round CRT, this has been reworked by Nuvac has a neck diameter of 32mm, overall length around 480mm.
It has quite a grainly looking Phospher in the screen, it is a straight gun assembly, i.e. not an ion trap. It does have a label that I think says Mazda 622 or 122, but again I can find no information on this CRT.
Attachment 234488

Attachment 234489

Attachment 234490

So if anyone can assist with finding data and what TV's these would have been in I would appreciate it.

Adrian

Re: Help with some old TV tubes.
 

The Cossor tube was most likely made by Mullard and will be an equivalent of the MW43-69. Possibly Cossor type 172K.
The 12" tube is a Mazda type, possibly a CRM121(A or B) if it has a 2volt heater.

DFWB.

Re: Help with some old TV tubes.
 

The round one could be a CRM-122? I’ve got an Ekco that used such a tube, can’t remember what the heater voltage was, try it on 2V and see how it looks.

Regards
Lloyd

Re: Help with some old TV tubes.
 

Brief data in the Ediswan 1954-55 booklet suggests the Mazda 122 might be a CRM122 which is 12" round screen (possibly not aluminised), triode gun. Designed for series heater configuration and has a Mazda Octal base.

VH = 7.3V @ 0.3A,
Typical operation:
Va = 9kV (10kV max)
Vg for cut off = -71V
Peak modulating voltage = 30V average for a peak of 150uA

Rich

Re: Help with some old TV tubes.
 

Thanks for that I have been googling for a 172K CRT without a lot of success. I have not applied any heater volts as without the information Knowing me i would do damage.


For the round tube after downloading lots and reading through things I have just found on frank.pocnet.net site a download on Mazda tubes and it I think it is as per the label a 122 tube or a CRM122 the it could be this: -
Attachment 234493

CRM122 12 inch round, 57 degrees, trode, non-aluminised, 7.3 V heater 0.3 A

I will have a search on that number to see if I can find more details and base pin out and what TV it was in.

Adrian

Re: Help with some old TV tubes.
 

I am reading and typing to slow looks like Lloyd and Rich beat me to it.

Adrian

Re: Help with some old TV tubes.
 

OK just downloaded a 1960 Ediswan book from fransk.pocnet and it lists it there with pin out thanks for the information. I do not know all the names of the companies and how they all merged so this information is of great help.

Adrian

Re: Help with some old TV tubes.
 

Brief info on Cossor 172K

Heater = 6.3V @ 0.3A
Final Anode V = 16kV max
Final Anode I = 150uA max
Vg = -60V (cut off)
Deflection angle 70 deg.
H-K Volts max = 150V
Capacitance, g = 8pF, k = 6pF
Ion Trap
B12A base, pin 1 = h, pin 2 = g, pin 7 = a2, pin 10 = a1. pin 11 = k, pin 12 = h
17" Rectangular

Rich

Re: Help with some old TV tubes.
 

I believe the Cossor 171K had a tetrode gun assembly and was similar or equivalent to the likes of the Emitron 17ASP4.
The Mullard Maintenance Manual informs us the the MW43-64 is a direct replacement for the Cossor 172K. Certainly, from 1957/8 all domestic Cossor CRTs were made be Mullard.
The Cossor 173K has the Mullard-Philips pentode gun assembly and was an MW43-69.
DFWB.

Re: Help with some old TV tubes.
 

Thank you Rich, can you possibly let me know what publication the information is in and I can look for it on line, It may help me stop asking these sort of questions?

I have done some testing with a home made CRT tester/checker and the pin out of the CRM122 is as follows: -
Attachment 234502

The base has been changed for a duodecal one, also I have powered up the heater from my power supply with a current limit of 300mA and the heater volts is as near as possible to 6.3 Volts, and with my little tester it is showing as it having a good emission. So I guess a few things were changed in the re-gun?

Adrian

Re: Help with some old TV tubes.
 

The Mazda CRM122 was used in the Ekco TU-211, very similar set to the T161. That’s the only set I’ve seen one in so far anyway! I’m sure others will know more.

Sounds like they fitted a 6.3V heater in that then, I don’t think it makes a lot of difference in the TV, my TU-211 actually has a Mullard MW-something fitted with a 6.3V heater, the original tube was completely knackered!

Regards
Lloyd

Re: Help with some old TV tubes.
 

Thanks DFWB, I have become a bit confused going through data sheets, I tend to use the pocnet site a lot and there is a MW43-69 and a MW43-69Z. The 69 says use the MW43-64 (non metal backed) data sheet for information and the 69Z must be an aluminised screen as it does not have an Ion trap,

I am getting confused by what is meant by metal backed as I see no differences in the glass and I do not think it refers to the aquadag, or does it? I could not see a point in aluminised screens also having an ion trap, so it must refer to something else, is it a metal cone within the glass envelope for the final anode?

Adrian

Re: Help with some old TV tubes.
 

The 14" Mullard may be the MW36-44. The Z suffix refers to the later gun fitted to the final production of the Duodecal based tubes. It was in fact the 110 degree gun fitted in the then current tube production [AW47-91 etc]. They were very good tubes. Slight modifications were required, new base connector, maybe alterations to accommodate electrostatic focus etc.

The Mazda tube being a regun is probably a replacement for the .3amp AC/DC tube CRM122 that was fitted with a 7.3v gun. Due to the difficulties of obtaining gun assemblies that matched the heater voltages of the originals it was not uncommon for regunners to fit standard guns with 6.3v heaters in tubes that had odd heater voltages. They were mostly series connected making a volt or two of no importance. In these cases the heater voltage was always marked on the tube. John.
PS Just checked the Nuvac label. Type Mazda 122.

Re: Help with some old TV tubes.
 

Now I am getting confused, the MW36-44 is still down as being magnetic focusing on the data sheet, but I did look at it and wonder if that would also be an alternative to my tube in the 991T, so I have just done a look though some service sheets for the 991T and it says that the MW36-44 was also fitted to this set with the addition of an external wire link between pin 7 and cathode. So a quick dash to my set, take the back off again and check the valve base, low and behold the pins are already wired :)

The only thing is it does not have a top cap anode as indicated in the data, perhaps this is really an addition to the contact on the side? or there could be a simple adaptor?

I love all this information, it just brings more questions.

Adrian

Re: Help with some old TV tubes.
 

Mullard made tubes probably have some small coding near or on the socket. Made in Holland tubes definitely do. Could you have a look for those?

Re: Help with some old TV tubes.
 

Nothing I can see on the CRT necks or otherwise. I know there are marks on Valves but on these nowt.

Adrian

Re: Help with some old TV tubes.
 

MW36-24 has a tetrode gun and the MW36-44 has the Philips pentode gun.
All Mullard 17" 70* CRTs including the metal cone MW43-43 have pentode guns.
Looking circuits of early Cossor 17" TVs such as the model 933 of 1953 the CRTs are drawn as having tetrode guns. The 171K and 172K are similar except for the possibility having been sourced from different suppliers. One might have been Electronic Tubes Ltd. ETEL.
https://www.gracesguide.co.uk/Electronic_Tubes

DFWB.

Re: Help with some old TV tubes.
 

Info for the Cossor 172K was obtained from Radio Valve Data, Eighth Ed. in section Television Cathode Ray Tubes page 57. Base diagram number is B12A number 10.

In the meantime I have been turning the place upside down to find the original Cossor Valves and Tubes book c.1956. Success! So far it confirms data in the ILIFFE publication and has a bit more info! Will try to scan later.

Also discovered another Cossor short form data book published in 1959 by which time 172K was obsolete. However information on receivers that used this CRT including 171K, advises it can be replaced with MW43-69 in the following models, 930, 933, 934, 935, 937, 939, 942, and 946.

Rich

Re: Help with some old TV tubes.
 

By 1958 almost all Cossor branded tubes made by Mullard had standard Pro-Electron codes, e.g. MW43-69 and the AW43-80 which was fitted in the model 948.
Circuit diagram of the model 945B shows that the 70* CRT has the pentode gun and therefore is a 173K or MW43-69.

DFWB.

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.

Adrian

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.

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.

Adrian

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.

Attachment 234510Attachment 234511

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.
Attachment 234512
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.

Adrian

Re: Help with some old TV tubes.
 

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

DFWB.

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.

Adrian

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

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?

Adrian

Re: Help with some old TV tubes.
 

The tube is a tetrode so it was not made by Mullard, more likely Electronic Tubes Ltd.

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.

Adrian

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:
Attachment 234547

I masked the neck and around the EHT connector with tape:
Attachment 234548

And the final result (not a very clear photo due to the black surface):
Attachment 234549

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

Re: Help with some old TV tubes.
 

Thanks Jac
These are a couple of pics of the condition
Attachment 234550Attachment 234551
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.

Adrian

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

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.

Adrian

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?

Adrian

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

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.

Adrian

Re: Help with some old TV tubes.
 

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

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.

Re: Help with some old TV tubes.
 

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

Re: Help with some old TV tubes.
 

Update.

I ordered a couple of cans of Graphit 33 yesterday and they arrived today, the graphite i had previously tried to apply would simply brush off the CRT, so I cleaned it up and wiped down with some Acetone again letting it dry off for a few hours.

The spray stuff is brilliant, it goes on well and does not run off the glass and it does have a good solvent smell with it, this evaporates quickly as the colour changes from a wet black to dull grey.

I have applied two coats and after a 10 minute wait , using the DVM probes gently resting on the coating approx 1 inch apart, I am getting 1K8 Ohm. I will let the CRT sit for a day in the garage to see if it gets any lower.

I was considering putting the CRT in the sun, but decided against it unless i could find a way of rotating it automatically, I would not want one side of the tube in the sun to expand against the cooler side in the shade.

I wonder if anyone with a colour printer has ever made up new Mullard CRT labels and warning papers to apply to a re-coated tube?

Adrian

Re: Help with some old TV tubes.
 

The coating went under 1K Ohms per inch after a 'polish' of the coating so very happy with the result. I have swapped the tube for the one in my TV, details in my Ferguson thread.

Adrian

Re: Help with some old TV tubes.
 

Excellent result!

Jac