CRT implosion

[MrBungle]

Good advice with the shelves. I have a dent in my work surface from where my HT fell off the shelf. Could have been much worse with a CRT down there.

[ColinTheAmpMan1]

Originally Posted by dsergeant

That was of course with an evacuated tube, if Jo Bloggs had taken one down without breaking the neck first there would have been a almighty bang.

To be a pedant for a moment, the CRT you mention was not "evacuated" as that would mean that it was still at very low pressure. It is, of course, not a "vacuum" but a very low pressure. The pumping will never get to a perfect vacuum, plus everything inside the glass envelope will have a vapour pressure, albeit very small. I used to work with mass-spectrometers, which need very low pressures indeed, but still not a perfect vacuum.

It is also worth knowing that the reason why the results of an implosion are that material is thrown around like an explosion is that air rushes into the evacuated volume so rapidly that if effectively gets over-pressurised and scatters the parts, rather than all those bits being sucked into what was the reduced-pressure volume. Of course, if the latter were to happen, the the implosion of a CRT would be pretty harmless, other than collecting the heap of bits of broken glass, etc.

Colin.

[malvision]

I always remember BBC TV Tomorrows World opening titles,showing CRT implosion. Not sure of the year was very young at that time

[radiograham]

Originally Posted by TonyDuell

My father (as above) once disposed of a defective TV CRT (not rimbanded) by putting an old coat over it in the back garden and throwing a club hammer at it. It made quite a 'Whoomp' but the glass was contained (and in very small pieces when the coat was lifted).

Personally I am happy to work on monitors/TVs with rimbanded CRTs, just being very careful. But I don't like the older type...

If I have to remove a CRT for any reason, I put it in a box surrounded with rags. Partly for its own safety. Don't just leave it on the floor of the workshop or you are likely to kick it by accident.


NEVER lift a CRT by the neck. Always make sure it's discharged before lifting it. The stored charge is not in itself all that dangerous but the shock might make you drop the CRT or jerk suddenly and hit the glass with a tool or something. And don't wear diamond jewellery when working on a CRT. You can easily scratch the glass and weaken it.

That brought back memories of my dad with a crt wrapped in a old coat,threw it out the back door and shut it quick,made quite a noise.

[slidertogrid]

I have replaced many tubes over the years in all my time I worked in the trade I never had a problem. I always treat tubes with respect but never thought of wearing protective gear. I even replaced a few early colour tubes in the customers home if it was a huge set and it was fairly easy to get the chassis out or to one side.
Back in the mid 70's the dustmen used to chuck old sets and tubes in the crusher and just jump out of the way as it went boom.

I smashed many old sets as a kid . Barrel Murphy sets and the like it was just seen as fun and sometimes they took some breaking!
In retrospect not only was it stupid and dangerous because of flying glass but also because of the dust from the phosphor...

More recently I am a lot more careful and worried ! I recently replaced a 19" unprotected tube in a dual standard set and this was done with goggles and thick clothing.
I disposed of a broken tube that had been "necked" at the tip as I didn't want to smash it into the landfill bin because of the phosphor going into the ground.
If you watch the videos of TV recycling they usually twist the tube base PCB to break the tube wearing gloves so it must be considered safe with all the health and safety regs in force these days.
It's just a case of being careful and responsible and not taking unnecessary risks, common sense really...
My few spare tubes are stored in thick boxes wrapped in old blankets in a temperature stable store.
I'm sure one day the health and safety brigade will consider old tv sets as dangerous risks to health and will enforce regulations.

Rich.

[FERNSEH]

Slidertogrid wrote: "I'm sure one day the health and safety brigade will consider old tv sets as dangerous risks to health and will enforce regulations."

When they come a knocking at our doors we'll have to deny that we own such dangerous equipment. Don't let them in!
Today I replaced the CRT in the Dynatron TV27A "Fulmar". The heater in the original Brimar C17BM has failed and nothing could be done to save it. The replacement is a Mazda 17BP4C. Same shape as the Brimar but has a tetrode gun which needs an ion trap magnet.

DFWB.

[bill knox]

Hi All

I left school at 16 and went to work at Decca Radio & TV when they were at Brixton Road, I was there for approx. 2 years.

At one time I was on the "Pretest Section" where 8 TV chassis complete with CRTs but no cabinets were on a trolley, where they were first turned on and set the picture up.

We were always hurrying up but was told to pull the trolley before pushing it forward and one particular time I pulled the trolley forward and the wheels were not in the correct position and the whole trolley went over and 8 CRTs went bang and glass went everywhere, I was standing approx. 3ft from the end of the trolley and I did not any glass in/on me but they were picking pieces of glass for days after.

All the boss said was clear the mess up and don't hold the line up

Bill

[sortedradio]

That sounds like a lucky escape Bill! It would have shook me up, however when we are young we no no fear.

[Heatercathodeshort]

Rich mentions replacing a few colour tubes in the customers house.
It brought back memories of a crazy situation involving the huge 70 degree 21" Mullard MW53-20 CRT and a Ferguson 308T.

The tube in the 308T had a partial heater short and the customer [Derby Road Wimbledon] agreed to have a rebuilt tube fitted.

I was 16 at the time and rode a Velocette Venom 500cc motorbike, my only form of transport at 16.

I removed the faulty tube then strapped it to the pillion seat on the Velo by means of a couple of bungee straps around the base of the neck to either side of the seat base. I rode it back to the tube rebuilder a distance of about 3 miles and collected the replacement in the same manner.

John Brown the owner of the rebuilding plant [Central Tubes] freaked out when he saw my transport especially when I removed the rebuilt tube from it's box and plonked it on the pillion.

Yes I managed to get it back to Derby Road and finished the job. Crazy days and when you're young, nothing is impossible. Regards, John.

[phut bang]

i can remember as a youngster throwing boulders at an old black and white TV this one had implosion guard (just a piece of glass to me then) throwing boulders harder and harder as couldn't break it, just a few chips in glass eventually the woden cabinet broke having removed the glass out of the way the next boulder at the tube resulted in tube imploding frightened me but thankfully the glass flying out didn't hit me. Many a tube provided entertainment after smashing them at our local tip.

[regentone001]

my mate and I would quite often carry naked crts on the bus with them on our laps crossing from one side of Coventry to the other. Only occasionally would a driver know what one was and not let us on the bus.
I do remember us taking an I think 70degree 21inch tube up to the local waste ground, already covered in rubble and all sorts of rubbish, and lobbing bricks at it from a safe distance when it went off it echoed 3 times between a row of houses on one side and a block of flats at least 100 yards away on the other. People came rushing out to see what was going on
Steve

[AC/HL]

They float face up in water (a mill pond in my case). Dropping a brick on them from behind a wall does a good impression of a depth charge. Few ponds left now, and you no longer find dumped woodies.

[mickm3for]

Talking of scratched tubes the delevery driver at the company i worked for was delevering a new Dynatron ctv in the luton van well the set was not secured and fell over and spent the next 15 miles sliding up and down the van on its tube face (looked like frosted glass) on his return, straight to the workshop saying could you polish this. the set was used as parts. It still worked ?

[ms660]

The worst scratched one I saw was due to a miracle that the CRT didn't implode...

Field engineer was at a customers house on New Road, Cadgwith in Cornwall, telly had to come in, he was running late and was in a rush, telly put in the back of the van and doors closed (allegedly) he drove off back to towards Helston, at this point I should point out that New Road leads down to the cove and it's down hill all the way and the van was pointing uphill....you can guess the rest, van doors shut to but not latched...breakout...CRT face down on the road trying to make high tide. It didn't make it all the way down to join the crabs but far enough down to wreck the face.

Lawrence.

[Heatercathodeshort]

Hello David,
Mazda 17BP4C. I have never heard of that one. Very much an American type number. It has a 'metal cone' sound to it such as the 17" Mullard MW43-43. Any chance of a picture? Little risk of an implosion if it is in fact metal. J.

[Restoration73]

Many years back I had to remove the crt base from a tube in a Philips (K35 I think)
anyway one of the pins came away with the base. I was able to gently tap the pin back
into the glass without mishap, and it functioned as normal. Phew !

[FERNSEH]

Originally Posted by Heatercathodeshort

Hello David,
Mazda 17BP4C. I have never heard of that one. Very much an American type number. It has a 'metal cone' sound to it such as the 17" Mullard MW43-43. Any chance of a picture? Little risk of an implosion if it is in fact metal. J.

Hi John,
The Mazda brand name was also used in France by the CIFTE company.
The 17BP4C is an all glass rectangular CRT and has an almost identical shape as the Brimar C17BM. Both tubes have a 6.3volt 0.6amp heater. 17BP4 has a tetrode gun so provision for the first anode requirement of 400volts has been made in the Dynatron TV27A.
Info: https://www.radiomuseum.org/dsp_hers...ompany_Id=9235

DFWB.

[Techman]

I've just been playing around testing a Mazda CRM151 this afternoon, (well it's yesterday afternoon now as it's now the early hours), and they're a big old 'bulb'! It's still in the cabinet at the moment, but will probably be being removed soon. When a tube implodes, all the glass flies into the centre and clashes together, shattering into even smaller pieces which carry on out the other side which makes it seem as if it's exploded - well that's the way I always understood it. I always wear safety goggles when removing and handling an old tube like that, as once you've lost your eyesight, it's game over!

[mark pirate]

I notice that quite a few posts describe various ways to pop a tube, I myself had great fun back in the 1970's climbing over the wall at the local tip when it was closed and used several methods to destroy CRT's

The sets were mainly old 405 line or dual standard B&W, but there was the occasional colour set.
The drill was to remove any valves that may be useful before dispatching the tube, usually with a brick or paving slab!

The biggest bang (and the most dangerous) was achieved by chucking sets on to a bonfire

How some of us survived our childhood must be a miracle!

Mark

[ekjdm14]

Having grown up in the '80s/'90s I've not had quite the same fun with imploding CRT's (most of them probably popped by Mark by that time! ) but one memorable one that created a helluva bang in my late teens was a c26" set I found in a skip & duly took down the back lanes to some waste ground with a couple of huge rockets (it being November). The rockets were inserted into holes broken through the top of the cabinet and blue touch paper lit, whence I retreated to behind a car door about 50 foot away.

My ears were ringing for a while after and pieces of glass and plastic rained down for a solid 20 seconds, my only regret (apart from the environmental ones now) was that I didn't have the set playing when it exploded!