How safe were re-gunned CRTs?

[slidertogrid]

The mention in the Baird thread about an 11X re-gun with cracked adhesive reminded me of a CRT I had implode in a set. Many smaller re-gunners didn't replace the rimband protection when they re-gunned a CRT.

I think it was Mullard that produced an advert for their Colourex re-guns explaining that they replaced the rimband and if I remember correctly they showed one of their CRTs being hit with a steel ball breaking a hole in the screen but with the tube holding together. another tube was shown with the same test imploding shattering in all directions.

The set I had a CRT implode in was a solid state GEC. I used to fit re-guns in place of the usually flat Toshiba CRT and used them for rentals.
A customer had a large dog and one day someone banged on their front bay window, the dog went berserk and dived into the bay knocking the set forward. The screen collided with the edge of a stone fireplace and the customer said there was a huge bang as the tube went off, as it had fallen on it's screen the glass didn't shower all over the room but I remember the tube had completely shattered, there was no glass left on the rimband.

After the initial shock of having a set wrecked I didn't really think anymore about it at the time but later on I did wonder it the re-gunning process (or heating during the process) had weakened the implosion protection in any way. These later 22" delta tubes didn't have the larger bonded rimband of the earlier 11X tubes I imagine the rimband was still bonded though?

I just wonder how many sets were fitted with re-gunned tubes with impaired implosion protection were 'out there'?
I stopped fitting re-gunned tubes once the delta sets had gone. Later 20AX and PIL sets were usually considered beyond economic repair once the tube wore out or were disposed of ex-rental while the tube was still OK, so I have no experience of later re-guns.
Did anyone else have re re-gunned rimband protected tube 'let go'?
Rich.

[agardiner]

Fitted lots of re-gunned tubes over the years; mainly 20" types. Never had a problem, but may of course have been lucky. All came from a company called Sunfen in Norwich, but I don't recall if they actually carried out the re-gunning process.

Stopped fitting re-gunned tubes as sets got bigger.

[Andrew2]

In the mono days we used Midland or Focus and never any problems. The Focus ones were a bit lively for the first hour or two on soak test, but they settled down and made nice pictures. I can't recall what we used in the colour era, probably Midland.

[its ur aerial]

I must have fitted literally hundreds of Regun CRT`s in my days with the Telly trade, some of very dubious quality, not mentioning any names But never had one brake.
The Focus name rings a bell, lots of flashing over and arcing
The majority of these would have been the Delta Gun type or Mono CRT`s.
Some of the necks on 14 inch colour tubes were a bit flimsy, but thats all.
Ken G6HZG.

[Vintage Engr]

In the early & mid 1960's I used a large quantity of re-gunned CRT's. Never had a problem with safety.
Rolling forward a few years though, I'd moved out of domestic TV & into Broadcast /Film. It was in the 1980's. One of our customers purchased a 27" Sony Profeel. This was part of a modular system, tuners, a Teletext unit, Viewdata and a Betamax machine, all could be linked together.

The client was a film maker & unknown to us at the time, was using the 27" monitor in a part of the production, where a TV image had to appear completely detached from any physical cabinet etc.

Some weeks later the client sent the unit back to me as a box of broken cabinet parts, with a 'naked' chassis, with the CRT only attached by the scan coils & tube base. It arrived on the back seat of a London Black Cab, with the driver perilously holding all the parts, & asking for the Technical Director..

One of the salesmen grabbed the chassis, whilst I carefully manhandled the CRT, all of it carefully placed on a sofa.
There was a note, to phone the client, whereupon he would tell us what he wanted us to do with it. (I probably should have told him..).
It wasn't until the cab driver had left that I realised that the 27" CRT no longer possessed a rimband.

The whole assembly, or should I say dis-assembly, was carefully taken up to our workshop. I phoned the client, who merely wanted us to rebuild the monitor, back to it's original state, - so he could sell it on.

I asked why & how they had removed the rimband. " With an angle-grinder" was the reply. I do remember very forcefully telling him that he was lucky to still be alive. As to rebuilding the Profeel, it wasn't going to happen!

I ended up keeping the chassis, replacing the CRT & then putting it into a spare Barco cabinet, together with a tuner, & took it home.

Quite how our man managed to carry out such a dangerous task, & get away with it I won't ever know. He actually had someone holding the CRT powered up with a picture on it, all whilst filming with a traditional 35mm cine camera.

I often say I had an unusual an interesting career..

David.

[agardiner]

That is one amazing story! Knocks my entire career of stories into nothing!

[Maarten]

Originally Posted by slidertogrid

The mention in the Baird thread about an 11X re-gun with cracked adhesive reminded me of a CRT I had implode in a set. Many smaller re-gunners didn't replace the rimband protection when they re-gunned a CRT.

Would there be any reason to do that, as the rimband was not anywhere near where they did their work so they did not have to remove it in the first place?

I think it was Mullard that produced an advert for their Colourex re-guns explaining that they replaced the rimband and if I remember correctly they showed one of their CRTs being hit with a steel ball breaking a hole in the screen but with the tube holding together. another tube was shown with the same test imploding shattering in all directions.

That sounds a bit like a (somewhat rigged) test of "no rimband" versus "rimband". Only in a tube that was down to air, there would have been a neat hole instead of most of the screen missing. The rimband mostly prevented glass from flying out, by directing the forces inward. It did not prevent the glass from shattering.

The set I had a CRT implode in was a solid state GEC. I used to fit re-guns in place of the usually flat Toshiba CRT and used them for rentals.
A customer had a large dog and one day someone banged on their front bay window, the dog went berserk and dived into the bay knocking the set forward. The screen collided with the edge of a stone fireplace and the customer said there was a huge bang as the tube went off, as it had fallen on it's screen the glass didn't shower all over the room but I remember the tube had completely shattered, there was no glass left on the rimband.

Arguably, the rimband might have done its job in that case. Did any glass come out of the back of the set? If not, the rimband did at least large part of its job.

[Maarten]

Originally Posted by Vintage Engr

Quite how our man managed to carry out such a dangerous task, & get away with it I won't ever know. He actually had someone holding the CRT powered up with a picture on it, all whilst filming with a traditional 35mm cine camera.

I often say I had an unusual an interesting career..

Very unusual and interesting indeed! Though the largest risk was not in removing the rimband itself or in carrying the tube without the rimband, but in the holding of the powered up tube. If somehow a conection would have come loose, the person who held the tube had gotten a shock and let loose of the tube, only then it would have become quite dangerous as the tube could have imploded forcefully all over the place.

[Nuvistor]

I was always wary of regunned Rimguard CRT’s, although I didn’t have any accidents with them I found the quality of the reguns poor. We tried a few different suppliers but life time was not good. Perhaps we chose poor suppliers but we changed to Mullard reguns and had no further problems, customers were happier with the results.
This was in tbe 1970’s, I don’t know about later CRT’s.

[HurtyAC]

Hello All, I used local re-gunned tubes by Ralf Stevenson Tubes a local to me tube rebuilder. They where very good. He pumped them hot and I never remember having any problems with them. I have to say customers didn't really break them. I agree on the comments about the solid state GEC that the glass didn't go off every where so the rimband did its job. An impact directly to the screen of that force would crack the whole faceplate and the result that it fell in on itself shows the rimband worked.
In the Broadcast industry which is were I moved to there where Barco CTVM2 colour monitors. To fit the tubes in these monitors you had to remove most of the tube mounting lugs just leaving a bit poking up and down on the original band. The tube would then fit within the monitor case. I would do this using a junior hacksaw, not a lot of lug for the bolt and washer to clamp to but that was the design. These monitors where used by most of the broadcast companies including the BBC and Thames who I both worked for over the 1980's
This is the last Ralf Stevenson tube I had re-gunned in 1980 in this ex Radio Rentals Baird badged set using the Thorn 2000 chassis

[Vintage Engr]

AS an addenda to my story of the "rim-bandless Trinitron" I had meant to add what actually happened next.

After persuading the client that a complete rebuild of the 27" Profeel wasn't economically viable, ((Parts of the caboiet & bracketry had been lost)he said that I could personaly keep the remains. The CRT functioned perfectly, but obviously was not safe, & also had of course, no fixing lugs. I reluctantly put a hammer to the end pip, & then purchase a re-gunned 27" Trinitron CRT.

Then the fun started. I can't recall which regun company I used. It was probably either Suffolk or Sabrina. Whichever company it was hadn't previously re-gunned a large Trinitron, but were confident that they could do it.
I received the tube, & fitted it, in it's 'New' reclaimed Barco cabinet. A couple of flashovers later it seemed to work, but the convergence could not be made anywhere near perfect.
A couple of hours later the awful truth dawned on me, after inspecting the tuble carefully. This was the type of Trinitron which had the concentric EHT/Convergence electrode connector...
I established that the gun assembly had been fitted upside-down, & therefore the springy connector that went inside from the neck up into the flare & thus to the convergence pin, wasn't connected.
The re-gunners tried to re-do it again, but it wasn't successful. I kept the chassis for ages, meaning to splash out on a new CRT, but like a lot of projects, it never happened, which was a shame, as I spent quite a lot of time in building the 'Barco-Tron'.
I later fitted a Mullard tube in the Barco cabinet & built a 'Bitsa' out of it Most of my early CTV's were hybrids in the sense that I cobbled together whatever boards I could scrounge to mak a working TV.

David.

[slidertogrid]

I found as others have said that the quality of re-gunned tubes varied, with Mullard being as good as a new tube. The firm I used was called Trent Tubes. They were based in Nottingham. The attraction was that they were cheap!

The price of some better brands meant that the set(s) would be beyond economic repair. I was using these in delta gun sets that were around 6 to 10 years old and probably only had an expected 5 or less years useful life left.

The Trent tubes would often flash over in the first few hours but usually settled down. Convergence sometimes wasn't always perfect but delta gun sets often weren't . Trent would always exchange a tube of it had phosphor 'dots' missing but again this was rare.

As far as to how safe they were implosion wise it is true this wasn't tested in any of the tubes I fitted with the exception of the one I mentioned. When these sets were withdrawn from rental it was usually because better, later more reliable sets had become available to replace them with. I remember scrapping or disposing of quite a few Pye Hybrids, G8s and 3500s that still worked or could have been repaired but were considered too old to re-rent by the early to mid '80s.

I wonder why Mullard replaced the rimband and advertised this fact if safety wasn't compromised. So far I have been unable to find a copy of the advert for Colourex tubes that I mentioned in my first post I feel sure it was in 'Television' magazine and was probably during the time when they were still re-gunning delta tubes so probably late '70s - early '80s.

If anyone finds this ad when looking at any old copies of the mag I would appreciate seeing a copy of it or the date of the mag and page number. Just so I can see that I didn't dream it!

[Mikey66]

Here you go...

[cmjones01]

Originally Posted by Maarten

That sounds a bit like a (somewhat rigged) test of "no rimband" versus "rimband". Only in a tube that was down to air, there would have been a neat hole instead of most of the screen missing. The rimband mostly prevented glass from flying out, by directing the forces inward. It did not prevent the glass from shattering.

A tube with a vacuum in it could still have a neat hole made by an impact. I saw this with my own eyes. When I was a child our neighbours had a Philips set with the G8 chassis (I think) which had the ultrasonic "clicker" channel change remote control. We used to play with their children. One day their father came to us and said that one of their boys had thrown a marble at his brother and it had hit the TV and gone through the screen! "There was a rush of air," he reported. I bet there was!

I saw the affected set, and there was indeed a neat round hole somewhat bigger than a marble pretty much in the middle of the screen, with no other damage. I think my dad managed to get the marble out by rolling the set on to its face, but that was about all that could be done...

Chris

[slidertogrid]

Originally Posted by Mikey66

Here you go...

That's the advert ! Many thanks. So Mullard are not actually saying a tube without the rimband renewed is dangerous, just suggesting that it might be and stating that they think it is best practice to renew the band and the adhesive as it may be compromised by the heating in the re-gunning process.
So the answer to my question is, in the opinion of Mullard is "not very" unless the rimband is replaced...

[Maarten]

Originally Posted by Mikey66

Here you go...

Ah, they do explain why they replace it.

Heating the tube during pumping could cause the adhesive between the tension band and the glass to fail.

I presume that could then later on cause the tube to come loose (sag inward or outwards of the set) and then have no real protection anymore when that happens. So if a tube that sits loose in its rimband is hit with too high a force, it might first sag inward and then implode. That would be dangerous.

If that's indeed the failure mode, I think it would be quite rare indeed but I can see why Mullard, readily having access to the rimbands and machinery to replace them, would choose to do so and also use it as an advertising point.

I can also imagine that smaller remanufacturing operations would probably deem it more dangerous to replace than to just leave it be.

P.S. Their test does indeed show the dangers of a tube without a rimband, so was indeed "rigged" the way I assumed it would be.

[German Dalek]

Hi all,
I made a bad experience with colour CRTs, which were re-gunned by "Colorvac".
That was a company here in Düsseldorf.
I talk about CRTs like A 66-410X, A 66-500X and familiar models.
Problem was, that they had HV-plate shorts!
These shorts killed the HV-sections.
WHY?
I never had a problem like that with b&w re-gunned CRTs, like MW 43-69,
AW 53-80 from "Otto Neller", made at Neuss.

Another problem was, that you don`t know, who was the maker of the gun.
Colorvac had choices, Philips, Telefunken or ITT, a customer told me that you
could ask him to take one of your own choice.

Regards,
German Dalek

[Niechcial,Steve]

I fitted a re-gunned A63-11x to a Bush D/S my family had . Within a week a 4 inch crack appeared diagonally down from one of the corners on the screen. Obviously it had the rimband else things would have been much worse. It had been rebuilt by a local re-builder near skegness (North Somercotes?) which the firm I worked for used a lot. They told me I was lucky they were going to give me an FOC replacement because many rebuilders diodn't guarantee against breakage (cheeky b------s). The replacement they gave me had lousy purity.
Later I was mass overhauling and selling ex-rental sets in London using a re-building firm on the Purley Way. I had one tube from them where all three guns went low emission very quickly. Another, where the tube neck fractured and broke off absolutely cleanly as if it had been cut . I presume that was the result of stresses set up in the glass when they welded the new gun on.

[Maarten]

They might not have used a polariscope to check for stresses, especially in case of that broken neck. Mullard would have, since they would have been used in normal production as well.

Though I still think regunned CRTs are reasonably safe, I'm starting to see why Mullard would have advertised their rebuilt tubes as better.

[Hybrid tellies]

Back in the 1970's up to the mid 1980's as a TV engineer fitted loads of regunned tubes of different makes from local firms to the likes of Mullard Colourex and Thorn New Life, with no safety problems or heard of any safety problems, in a wide range of TV's ;

For Black and White, 17" 20" and 24"

For Colour, 19", 22" and 26" and some 17" and 18" all delta gun of course.