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Ekco T.U. 211, A possibly pointless restoration!

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Lloyd
(@lloyd)
Noble V-Ratter Registered

Since there were complaints about the lack of 405 line telly threads, I thought I'd try and do something about it, so here's my effort!

front-of-set.jpg

This is an Ekco TU 211 405 line single channel TV with 12" (or there abouts) screen. It was made in the mid 1950's, the exact year I don't know, as someone put a black blob over the date stamp underneath! It was made in April though, if that is important...

I was drawn to this set at the NVCF in 2015, as I'd quite liked the appearance of the T165, but couldn't find one, and this looks similar, so thought it'll do! Got it for £40, condition isn't bad, but could do with some attention on the curved edge as the finish has crackled and looks lighter, as if it'll flake off if you look at it wrong. The 3 control knobs on the side look to have begun decomposing, much like the LOPT casings on some of Ekco's TV's, though no bad enough to make them fall to bits.

On getting it home, and removing the back, I noticed something rather worrying, an extra resistor hanging from the dropper, and connected to one of the CRT base heater pins.

spot-the-evil-bodge-resisto.jpg

I decided the best course of action was to try and get some life out of it, without the bodge resistor, so it was removed, and the tappings set correctly for 240V. I also found that there is a small socket for an add on aerial amplifier which needs 2 pins bridging to make up the heater circuit. with this done, it came to life (after a few explosions!) and with the RBM EHT meter connected I could get 9KV EHT, not bad for a set full of waxies! As expected, the tube is as flat as a flat thing can be... Possibly even flatter! There was barely a glow on the phosphor, with the lights off, I could just see it! There is also a rather odd looking milky getter in the base of the tube, so it's probably got a bit of wind...

EHT-reading.jpg

milky-getter.jpg

spot-the-exploded-caps.jpg

first-light.jpg

With the tube confirmed a zombie, I thought I'd try powering it from the bench power supply, I connected it all, and isolated the heater from the heater chain. I had the heater voltage up to 12V and managed a rather wishy washy test card, still rather dim.

over-voltage-heater.jpg

Just for a bit of entertainment, I thought I'd have a go at 'cathode imaging' to see what state the cathode was really in. For this I used the bench power supply, and a 1000V Megger for the EHT. I also removed the focus assembly. With it all connected up and the test button pressed on the Megger, we had light! It was very dim, but I could see the state of the cathode. It looked like the moon coming from behind a cloud, with not much emissive surface left at all.

cathode-image.jpg

At this point, I thought to myself ' well that's £40 down the bog...' and with that, the set was stuffed in a corner, awaiting a new CRM-122.

crt-label.jpg

Fast forward to 2017, the set has been safely stored away at my Nan's house since just before we moved to Lincolnshire, in December 2015. With the new workshop almost complete (but still a mess!) I decided to bring it out of storage along with a few others. My Nan's cat watched proceedings at the top of the stairs, waiting to try and trip me over! He eventually got bored of that and decided to take up residence on top of one of the other sets I was bringing back! Why do cat's like to sit on top of TV sets?

cat-on-a-telly.jpg

So after a day in Lincoln at yet another job interview, I decided I needed to unwind, so thought what better way than with a knackered old telly? It was connected up to the workshop RF system and powered up, the result was just a blank raster! Clicking round the channels on the Aurora didn't bring up anything. Without any service data I am a bit in the dark, but thought it'd be a good idea to ditch the few waxies I could see, and observe the results. There were also loads of those horrid capacitors that look like round ended fat resistors, the same as you find in the TMB272, and they were all duff in that set! 3 had already exploded. I followed the heater wiring and snipped the leads to all the decouplers. I also managed to find the audio output section and replaced the grid capacitor, which was checked and found to be leaking badly. With all this done, I could get the test card again, but without sound. The audio stage was working as touching the multimeter probe on some of the valve pins in the audio staged produced buzzing and crackles. A quick twiddle of one of the IF cores (the one with a yellow tip on the adjuster) brought in the sound loud and clear, and also improved the picture, which is still so dim you need the lights off to see it.

finally-a-test-card.jpg

under-chassis-before.jpg

under-chassis-after.jpg

Latest-TCC-improved-lineari.jpg

And that is as far as I've got, The chassis is out currently for a much needed dusting, and whilst I'm at it, I'll give the tube a clean too, not that it'll improve it at all, but at least I won't get covered in black stuff every time I brush past it!

IMG_4262.jpg

 

Regards,

Lloyd.

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Topic starter Posted : 01/03/2017 3:24 am
PYE625
(@pye625)
Famed V-Ratter Registered

Hi Lloyd, well I don't think it is a pointless restoration because you will end up with a nice set and you are doing a great job with it so far. OK, the tube is shot but a replacement could come your way in the future, so it's still a worthwhile restoration.

thumb_gif

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Posted : 01/03/2017 8:43 am
freya
(@freya)
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I have a TU169 that had its cathode looking like that, I put it on the radar rejuvenator and gave it a blast on setting 4 as it would not respond to anything less, The result was instantaneous success and a cathode that was as dark as an eclipse to almost full coverage of brightness.

My assumption was the cathode had been poisoned.

Not saying that's going to be the case in your scenario as the botched heater supply could have done much more damage to the slow heated tube.

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Posted : 01/03/2017 10:33 am
Marc
 Marc
(@marc)
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Hi Lloyd,

It's great to see you back at the bench again, you've been missed.

I'll echo Andrews comments, carry on with it 'as is' for now, a CRT will turn up one day or try Freya's idea if you have a rejuvenator give it a bop....you've nothing to loose.

Marc.

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Posted : 01/03/2017 1:14 pm
freya
(@freya)
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By slow heated tube, I should elaborate that the CRT is a slow heated type as is the 6D3 delay diode.

This is done by using the 6D3 in the CRT Grid feed that keeps the Grid at chassis potential, this prevents EHT and HT reaching the CRT until the heaters have reached their correct temperatures.

My radar 202 is the only make of rejuvenator that I have success with on the Mazda Triodes.

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Posted : 01/03/2017 1:15 pm
Lloyd
(@lloyd)
Noble V-Ratter Registered

Cheers for the encouragement! It is nice to be back at the bench, Marc, although, I  haven't made it to the bench yet, it's still covered in all sorts of junk!

Interesting about the delay diode function. I'll have to try giving the tube a kick (not with my foot!), all I have is a B&K, so it's probably too gentle to do anything. I did have one thought, I could borrow the CRT from my Murphy V180, I'd have to use a transformer to supply the 2V heater, but that should be fairly easy to do. I also have a Murphy V230 that I could possibly borrow the tube from, but it'll require more messing about.

I made a mistake in the original post, about looking for an Ekco T165, I actually meant T161! I don't think there ever was a T165...

Something else I need to do, replace the electrolytic can, one section had already been disconnected, and re-routed to a big 100µF can neatly mounted on it's own clamp under the chassis. Whilst running the set yesterday I noticed that the replacement was running warm, so I replaced the replacement with a modern 100µF tacked onto the tag of the original can, which runs cool. Once the chassis was out, I could see the markings on the original Hunts can, it is 60µF and 250µF in one can, and the 60µF is the one that has been replaced with 100µF! So I'll be replacing the replacement of the replacement with something closer to original value. I'll replace the 250 as well, possibly re-stuff the can, as it too was getting warm.

I need to go capacitor shopping now, as I needed a 0.05µF in the frame circuit, but didn't have anything suitable in stock, so I tacked in 2 0.02µF caps until I can get some. Also need something to replace those horrid little 'resistor style' caps.

Today's main task is to finish cleaning the CRT and it's mountings, take the case outside and blow at it to shift some more dust, then re-assemble it all. I'll take some shots of the tube mounting and mask too, as it's quite interesting to see how it fits together. There was actually no dust or dirt between the tube face and the implosion guard, due to a rubber seal that is still as elastic and flexible as it was when it was new.

Regards,

Lloyd.

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Topic starter Posted : 01/03/2017 2:23 pm
freya
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Good luck with the B&K, I never got mine (467) to work with the triode tubes hence the Radar. Not sure why it isn't compatible.

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Posted : 01/03/2017 2:41 pm
Cathovisor
(@cathovisor)
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Forgive this old sceptic, but how do you know that what you are seeing on the screen is an image of the emissive surface of the cathode? Would someone explain the mechanism to me? 

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Posted : 01/03/2017 2:42 pm
Cathovisor
(@cathovisor)
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freya said
Good luck with the B&K, I never got mine (467) to work with the triode tubes hence the Radar. Not sure why it isn't compatible.  

The way 467s work and the way they measure cathode current preclude their use with triode tubes - it needs to be a tetrode gun at least. I think I once looked at making a custom adaptor but it came to naught. 

It's been suggested the best CRT tester for older B/W CRTs is the Beamec. 

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Posted : 01/03/2017 2:49 pm
crustytv
(@crustytv)
Vrat Founder Admin

Cathovisor said
Forgive this old sceptic, but how do you know that what you are seeing on the screen is an image of the emissive surface of the cathode? Would someone explain the mechanism to me?   

I can't explain how or why it does it but what Lloyd has demonstrated is an image of the CRT cathode surface.

The procedure has been well documented in a number of period books, here is just one such example from 1953. As to a more technical explanation, I leave that to others.

cathode.jpg

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Posted : 01/03/2017 4:54 pm
PYE625
(@pye625)
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I believe a way in which it can be done is to magnify and photograph the screen dot that is sometimes visible when the set is switched off. 

The images above I think were photographed by John Cura and they are in a little book called "Television picture faults" or something similar to that title.

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Posted : 01/03/2017 6:54 pm
Anonymous
 Anonymous
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Cathovisor said
Forgive this old sceptic, but how do you know that what you are seeing on the screen is an image of the emissive surface of the cathode? Would someone explain the mechanism to me?   

The electrodes in a CRT (or camera tube for that matter) form a lens that focus the electrons from the cathode surface onto the screen (or target in the case of a camera tube) The electron stream is brought to focus by the equi-potentials on the cylindrical electrodes, and may also be limited by the aperture in the anode (in a diode gun camera tube, for example)

By shutting off the deflection currents and magnetic focus (if fitted) and manipulating the anode voltage (typically by reducing the EHT voltage to about one third of normal) it is possible to expand the electron beam bundle at the screen, so that the resulting cathode image is about 10% of the screen size. Ideally the cathode surface should be active over the entire surface, and the image seen at the screen uniformly bright.

If the cathode is damaged, due to chemical poisoning or physical damage, those areas will be non-emitting and show as dark on the screen image. With some experience it is possible to diagnose the malady, which may have resulted from defective manufacture, aging, or excessive cathode current draw.

This is a very handy quick check and was done often on the test stands when I worked in a CRT factory.

It is possible to rejuvenate a damaged cathode, as is typically done in the TV service trade (and here by restorers). Cathode blasting is somewhat of a "do or die" step and may make the CRT worse! 

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Posted : 01/03/2017 7:01 pm
Lloyd
(@lloyd)
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The cathode imaging I'd heard mention of a while ago, mostly on very early sets with mains EHT. I first tried it on a Motorolla TV with electrostatic deflection CRT, I wanted to see if the tube was any good, so as it used quite a low EHT I thought I might be able to see something using just the 1000V of the Megger, and to my surprise it worked! And the tube in the little Motorolla proved to have plenty of life in it. Trying it on a tube as big as this was a bit of a gamble, Such a low EHT voltage might do nothing, but again to my surprise it displayed a nice blob, albeit very dim. I did also try it with the EHT from one of those little 5" black and white mini TV's, with about 10KV, the result was a much brighter and more focused spot. I'm actually thinking of building a pocket-sized unit that I could take along to places like the NVCF so I can test CRT's in potential purchases (providing the seller will let me!), that way I'll avoid buying any more sets with dud tubes.

Back to the Ekco, Yesterday was spent cleaning up the CRT, it's mounting cradle, the mask, inside the cabinet, and the speaker grille. By the time I'd finished, my hands looked like that of a coal miner! I'm pretty sure this set was used in a house with an open coal fire, as the smell of the black dust is that of coal. I found another date stamp on the implosion guard, 10th of June 1953, so later than the April date on the cabinet. The CRT is an Ediswan CRM/122, I've never encountered an Ediswan branded tube before. Looking between the phosphor and the internal coating you can see right down inside the neck of the tube, and it feels really lightweight and thin! Quite scary to think it's under so much pressure.

I also chopped up the dual can electrolytic and used it to mount some new capacitors. the reason for the death of the 60µF section was obvious once opened, the leadout wire from the roll of paper and foil had rotted off just before it got to the rivet. I could have left the original can alone, with just 1 section working, but I didn't like having random caps dangling under chassis, and thought it'd be neater if they were in the correct place, and solidly mounted to something. With that done, I can hide the new parts with the old can, I just need to clean it out as it's full of pitch and remnants of the old capacitor innards.

With the cabinet and tube all clean, it was re-assembled and the chassis slid back into place. That is as far as I've got, today's tasks are to put the chassis screws back in, and tidy a few more bits up, then try finding some service data! I've got 3 out of 4 pages of the T161 / TU169 data, which looks similar. I've also got 2 of the red books, so maybe it'll be in one of those.

Regards,

Lloyd.

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Topic starter Posted : 02/03/2017 11:00 am
Nuvistor
(@nuvistor)
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Lloyd said
Back to the Ekco, Yesterday was spent cleaning up the CRT, it's mounting cradle, the mask, inside the cabinet, and the speaker grille. By the time I'd finished, my hands looked like that of a coal miner! I'm pretty sure this set was used in a house with an open coal fire, as the smell of the black dust is that of coal. 

TV repair wasn't a clean job, all sets from houses with coal fires, the majority in the area I worked, were thick with dust, the EHT cable could be twice the normal diameter with build up of dust. Every job required the vacuum cleaner, the dust was a fire hazard so had to be removed.

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Posted : 02/03/2017 11:16 am
Till Eulenspiegel
(@till)
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The Mazda CRM122 was created for universal mains receivers that employed a series heater chain, hence the strange 7.3volt 0.3amp heater.  The CRM 121B or CRM123 can be employed if a 2volt heater transformer is fitted.  Alternatively, the Mullard MW31-16 or 74 can be considered as long as a first anode supply can be found. Worth bearing in mind the Mullard tube has a slightly less diameter faceplate than the Mazda. Another CRT to consider is the Mazda CRM124 as used in the Murphy V230.  The CRM124 has a tetrode gun so provision for first the anode and  is necessary.  All the tubes mentioned here have the 35mm neck. 

Till Eulenspiegel.

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Posted : 02/03/2017 11:22 am
freya
(@freya)
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As usual being an Ekco, I have the Genuine data for this is you want it, either PM me your email or I will scan and email to Chris.

I still don't get emails notifying me of posts on threads I have commented on, strange as I don't seem to be able to find the area of preferences I need to change to enable this.

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Posted : 02/03/2017 5:33 pm
Nuvistor
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Not tried it but does the Subscribe button at the bottom of the thread send emails on new posts? 

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Posted : 02/03/2017 6:12 pm
crustytv
(@crustytv)
Vrat Founder Admin

freya said
I still don't get emails notifying me of posts on threads I have commented on, strange as I don't seem to be able to find the area of preferences I need to change to enable this.  

See here

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Posted : 02/03/2017 6:28 pm
freya
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Thanks Chris, that's made things easier

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Posted : 02/03/2017 7:33 pm
PYE625
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nuvistor said

TV repair wasn't a clean job, all sets from houses with coal fires, the majority in the area I worked, were thick with dust, the EHT cable could be twice the normal diameter with build up of dust. Every job required the vacuum cleaner, the dust was a fire hazard so had to be removed.  

I can still remember the sight of foam cleaner running down the front of a nicotine covered set as it made brown pools of liquid on the bench..... Ah the good old days of refurbishing ex-rental sets at the co-op.

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Posted : 02/03/2017 8:08 pm
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