TV22 tube replacement

[tvden]

Hi all I have the chance to buy a tv22 with a low emission tube !!! am I right in thinking I could use a tube from a Ekco TMB272 as a replacement may thanks Den

[oldeurope]

Did you see the picture or did you measure it bad?
After a few hours of working my TV22 CRT is like a new one

Kind regards
Darius

[tvden]

Hi Darius, I havent seen this set yet, the guy just told me it was low emission on the tube, and I did not want to buy it unless I could fix it which is why I was asking if the TMB tube would fit, it may well take a booster, I have to go to his house on my way back from holiday I will let you know what happens regards Den

[high_vacuum_house]

Hello there,
You could try using a reactivator for the CRT but I haven't tried this methood or you could boost the heater (warming it up a bit more than normal) Although these methoods may not last very long before the emission falls off again.

If the CRT is a bit gassy you could try firing the getter again (like on the CRT I bought at the NEC which worked (see thread on sucess on re gettering CRT))
If it is not possible to fire the CRT electrically you could try someone with an induction heater to fire it. A gear making company may have one although I haven't tried this methood.
You can always try Crowthorn tubes as they have a few 9" CRT's on Ebay at the moment (orange and blue phosphor ones though )

Regards,
Christopher Capener

[oldeurope]

Good morning,

Hi Danny, in the TV 22 you have 0,3A and the Mazda's I know have 12,6V
0,3A. So you don't need a heater tranny.

Hi Christopher, if you heat it too much and you loose emission, you have no
chance to rejuvenate it. Get some practise with radio valves and you'll
get success.
Where did you get the information that a gasy crt causes low emission?
I have a lot of gasy valves and they are very good. But with high tension
they light up like a neon bulb.
I have an indictive heater. But often you make the valve gasy with it!
Your idea with the electrical getter is wounderfull, but I want a replacement
first before I test this. My LV20 is going better and better since I used it
first. In the picture you can see my LV20 the pos. of the picture is not
well adjusted.

Hi Den In my TV22 the voltage drop on the "Birmistor" was so high that
I did not get the 0,3A. I am sure you have the same problem there and
the CRT will be ok after a few hours working. When the set is well repaired.

Kind regards
Darius

[Duke_Nukem]

Where did you get the information that a gasy crt causes low emission?

If you run a slightly gassy tube, lots of +ve ions are created which slam into the cathode and recks it very quickly indeed.

Also, although we think of an "oxide" cathode, what actually happens is a electrolysis during manufacturing that brings a thin (atoms!) layer of metal to the cathode surface and this is where emission takes place. I bet this thin layer would be only too happy to re-combine with any oxygen molecules that come its way.

Originally Posted by Darius

After a few hours of working my TV22 CRT is like a new one

I've experienced this too. The CRT on my HMV2805 tested as a wee bit low emission but I chose to resist its getting a quicky "boost". The CRT now gives a very good picture.

Originally Posted by Bsaden

...could use a tube from a Ekco TMB272 as a replacement ...

I've heard several people say that it is possible although it'll take a bit of mechanical "tweaking". of the TV22's mechanics ?

TTFN,
Jon

[Panrock]

Originally Posted by Duke_Nukem

I've experienced this too. The CRT on my HMV2805 tested as a wee bit low emission but I chose to resist its getting a quicky "boost". The CRT now gives a very good picture.

Agreed Jon, and the CRM123 I got for the Ambassador TV4 I did recently also tested as decidedly weak. But in practice it gave a sharp, 'daylight-brite' picture! Given a screen in good condition it seems you don't need many microamps to do the job...

[grindrod]

My TV12a tube has improved with use, certainly Darius is correct about the Brimistor, you must check the heater chain current and adjust the dropper tap to give 0.3A, also then check the DC HT voltage, if the rectifier is OK then adjust the HT tapping to give the correct HT, you will be amazed at how much improvement can be gained by just attending to the above!!!

The Brimistors age and then the hot resistance increases, it is always worth looking out for some on scrap chassis, modern devices are much too low in resistance.

Tube rejuvenation often used a circuit to apply forward bias to the control grid so that several milliamps of grid current would flow, i have a circuit in an old Practical Television magazine, I wouldn't like to try it on any of my tubes though! Better a dull picture than a dead tube!! Has anyone tried it?

Cheers, Martin

[tvden]

Hi all I am taking all your posts onboard, most of your comments can also be applied to my Bush 11a and 12a both of which I have only just aquired and havent touched as yet!!! I am prob puting off the moment, ok I looked in the back when I bought them and all seemed ok the correct chassis, red soldiers ect and the guy said they were working when put away 35 yrs ago Gulp !!! they look as if they have never been touched judging by the 2 inches of muck inside but one can never take anything for granted in old tv land when I do start these two sets I intend to do them one after the other as most of the info will be fresh in my mind regards Den