CRT implosion

[dsergeant]

Some years ago when I was disposing of a set I cracked off the neck - itself fairly tame, nothing more than a rush of air under the towel I had put over it. Took it down to our tip where the general waste goes in a heap the other side of a wall some feet down. Asked the bloke what to do with this telly tube - 'just throw it over there' he said. So I did. Enormous crash and glass everywhere - well away from me but wouldn't have been good if workmen were working down there. 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.

I have always treated tubes with respect. Fortunately never witnessed an uncontrolled implosion.

[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.

[Maarten]

Of course in the smaller factories and rebuilding operations they lifted the tubes by the neck all the time, I'm sure that resulted in a big bang some of the time.

They probably wore protective clothing, though. I know for sure they used kevlar reinforced gloves in the last Dutch CRT factory that was closed down a few years ago.

[FERNSEH]

Remember even with the P band CRTs the faceplate has the implosion protection but the rear part of the tube, the cone, isn't protected.

I remember one East European 24" CRT allegedly protected with a P band imploded violently when we threw stones at it.

The Baird T5 tube is a scary thing. A special cradle was made to ease the horrors of removing it from the set and to keep it safe.

DFWB.

[peterpixel]

Any type of crt when it is out of its mounting will be stored face down, away from the work area,on a piece of soft cloth to protect from scratches.Hours of polishing with jewellers rouge may be needed if you don't.Peter.

[Nuvistor]

I always worried about the integrity of the third party regunned Rimband/Panorama CRT,s. Colour ones very often were replaced by Mullard or Mazda reguns under warranty, just under 4 years old. I usually fitted Makers reguned mono or colour Rimbands for that reason.

I also never found a third party regunned CRT that was as good as the makers. I know others did but after a few non to favourable experiences with them I stopped using them. These were not rental sets, I could pass the cost on but the few bad experiences did not do my reputation any good. Fitted those few with a makers regunned one and took the cost hit, worth it for customer satisfaction but not the pocket.

[Peter.N.]

I have broken many, both accidentally and deliberately. Usually there is just a loud hiss when the neck gets knocked off in accidental breakages but when I was buying lots of ex rental sets I was disposing of many of my older ones into a skip and you can get a lot more in if you break the CRTs, if you hit the screen they do go off with a very loud bang, but if you just knock the neck off with a spade you can then break then rest of the glass comparatively easily.

Back in the '50s a friend of mine had a round CRT TV in his bedroom and the tube spontaneously exploded / imploded and there were bits of glass all over the room, fortunately it wasn't occupied at the time. Never heard of that happening again, although it probably has.

Peter

[Nuvistor]

One dealer in a Wigan had one go in his shop window, wasn’t a Rimband, had the normal safety glass. No damage externally, all contained within the cabinet.
He decided against having sets in the window in full sunlight, it was a hot and sunny day, whether there was a fault weakening the glass or just the heat I don’t know. The shop was in Permberton, Wigan, forgotten the name.

[vidjoman]

Back in the early 60’s where I worked we had a guy who regunned tubes. He had an accident one day when his van overturned and about 6 tubes went bang. He didn’t actually hear them as he was very deaf. However with glass everywhere he decided to ‘crack’ the neck from then on. He would use a glass cutter to score around the neck near the pin end, which he needed to do anyway to re-gun, and crack the neck with a sharp knock. The vacuum was gradually reduced as the air slowly entered via the crack. A few years later we got the rimband tubes that didn’t go bang if you accidentally hit the front.

[ionburn]

I remember getting rid of the vacuum in a tube a number of times back in the day (more modern tubes) by the usual method of pliers on the nipple, but was always wary and covered the tube. Over the years I have seen accidents but all embarrasing and expensive rather than injury producing. I think the scariest moment for me was when I went to a local tube regunning workshop one day and one of the guys in there had just completed removing a deep scratch from the face. It probably looked worse than it was due to the thickness of the glass but the resultant 'dent' looked deep to me. I think it was perhaps more the pride of the work as the tube was scrapped as (obviously) optically useless.

[McMurdo]

I keep my Pye VT4 next to my bed. Bad idea?

[Lloyd 1985]

I probably should wear gloves and thick clothing when handling tubes, but if I’m honest, I never have I wear glasses anyway, not that they would stop any bits of flying glass, if you are lucky enough not to need glasses at all then I would strongly suggest investing in some safety glasses, just in case! I have some, but they don’t fit over my existing glasses, so are a bit impractical, and I can never find them when I want them!

When working on a chassis with a tube fitted I don’t take precautions against implosion, and have never really given it a thought, you’ll find quite a few sets where the tube stays in the cabinet, or if it does stay on the chassis, it just makes things more difficult, I have a Philips 385U tv that is just plain scary when it’s out of the cabinet, the tube is only clamped in place by its neck, and the front of the bowl is balanced on 2 little bits of bent metal with a bit of something soft stuck on it! Luckily the set can be worked on in its cabinet, with access to all the components underneath. The Bush TV22 is the only set that I think the tube is ‘safe’ when the cabinet is off, as it’s held by the front of the bowl by a brass strip, and also clamped at the neck too, although the brass strip can and does snap on some sets, and then the tube can become loose.

Regards
Lloyd

[Heatercathodeshort]

I have serviced and handled CRTs since I was 11 years old. You just have to be sensible and by all means wear eye protection when handling pre 1965 tubes.

I have known of only one self implosion caused entirely by myself. I overhauled a GEC BT302 17" table model. It was the late 1960s. The overhaul involved fitting a replacement tube and the old metal finned HT rectifier mounted immediately under the CRT bowl.

I replaced the rectifier with the then BY100 silicon diode and a 25 ohm 10 watt surge limiter resistor. I did this while waiting for the tube to arrive. With the new tube fitted the chassis was set up, soak tested and returned to the customer.

The following morning I had a telephone call from my customer. 'We had all gone to bed and around 2.30 am there was a very large bang. We all got up and searched the house but could find nothing wrong. The following morning my wife said she could see the works of the television through the screen...'

To cut a long story short, the 25 ohm resistor was actually touching the bowl of the tube and had caused extreme local heating stressing the glass . It must have given way in the early hours. It would not have happened if a tube had been in place when I carried out the HT mod as I would have seen the risk and positioned it safely. The only damage to the chassis was a broken 30F5 IF amplifier valve.

The customer was a very wealthy man from Kingston Hill but was jolly decent about the incident and accepted a replacement tube FOC of course!

Just be sensible when handling CRTs and NEVER carry more than one at a time. I remember a guy carrying a couple of 9" tubes and he knocked them together when attempting to open a door. Both imploded but thankfully no cuts or bruises. Moving from hot areas to cold should be avoided.

Mazda round tubes are incredibly thin and I have handled huge numbers including the time bomb 15" CRM151 used in The Ekco TC113 and others. I have never experienced an implosion and talking to a couple of my old colleagues, neither have they.

DON'T HAVE A SHELF ABOVE YOUR WORKBENCH WITH ITEMS THAT MAY FALL AND IMPLODE TUBES ON CHASSIS YOU ARE WORKING ON. Think about that one.

Thin gloves if you feel safer but thick ones can cause clumsiness and an extra hazard.

Don't get paranoid! Regards, John.

[sortedradio]

Thank you all, some very good points made and duly noted.
"Don't get paranoid! Regards, John. "
Thank you John, I feel re assured now.

[johntech]

Having spent over 40 years in the TV servicing trade I only remember one nasty occurence.
We had fitted an early 25inch regunned colour tube to a Bush console TV and returned it to the customer.
During the night the tube imploded. I had to go to see the customer the following day there were sheards of glass everywere. As it was I suppose the late 60's the customer seemed happy to agree it was just one of those things ! I suspect if it happened today our company would have been in court.
From that day on we only used Mullard and Mazda reguns !
Before we scrapped sets we would knock the neck of the crt resulting in a quick intake of air nothing drastic.
I watched a TV programme on re-cycling a few years ago where they drilled a small hole through the EHT connector to to relieve the vacuum much less dramatic.

[Refugee]

On the odd occasion I have been scrapping a TV I drilled the EHT connector. The vacuum fills up with air in a minute or two. It is nothing like as fast as knocking the neck off.
The glass can then be knocked off the tube in smallish bits over the land fill bin.
It saves quite a bit of bin space.

[AC/HL]

My only nasty occurrence in changing a CRT was once early on I'd got everything back together and cleaned the face, but I'd left the tube a touch forward. Sliding in the reinforced glass front scratched the (regunned) tube face!

[mark pirate]

DON'T HAVE A SHELF ABOVE YOUR WORKBENCH WITH ITEMS THAT MAY FALL AND IMPLODE TUBES ON CHASSIS YOU ARE WORKING ON.

A very valid point, my old workshop had a large shelf above to house test equipment, this was never a problem until I put an old mains transformer up there during a bench tidy.
A few days later when repairing a music centre, I caught the transformer with my sleeve, it crashed down destroying the plastic cover

Thank god it was not the back of a CRT!

The Bush TV22 is the only set that I think the tube is ‘safe’ when the cabinet is off, as it’s held by the front of the bowl by a brass strip, and also clamped at the neck too, although the brass strip can and does snap on some sets, and then the tube can become loose.

The first time I removed the chassis from a Bush TV24, I was not aware that the bowl just rested on the plywood, the tube face had stuck to the mask and was pulled forward as I removed the chassis, it was left hanging by a clamp round the neck!
Luckily both myself and the CRT survived intact!

I am generally very careful when handling CRT's, especially early round tubes.
15" Mazda tubes & EMI narrow angle tubes are made of very thin glass and are about 70 years old, this is scary enough on it's own, but many tubes of this age have glass defects (bubbles and cracks in the tube face).

ALWAYS take extreme care not to stress or knock them, and ALWAYS use eye protection when handling!

Mark

[sortedradio]

"DON'T HAVE A SHELF ABOVE YOUR WORKBENCH WITH ITEMS THAT MAY FALL AND IMPLODE TUBES ON CHASSIS YOU ARE WORKING ON." - John

Yes this is very good advice. I have shelfs above my workbench and the lower one is doudle width so ends up being full of odds and sods. That will change this weekend!

[Lloyd 1985]

My old workshop had a several shelves above the bench space, mainly because of space constraints, luckily nothing ever fell off onto a set! Best thing I ever did in that workshop was to have an old round dining table at one end and used that to work on a few sets, it was great! No more needing to turn the chassis round on the bench to get to the other side, just walk around the table! And because it was in the middle of the room, there was no where to put shelves above it. Sadly I had to leave it behind when we moved My new workshop is in a 16 x 8 shed, which I built with a little help from scratch, and one of the things I insisted on when it was built was to get some old double glazed windows from somewhere, I ended up getting some brand new ones from a company down the road for a bargain price, and my work bench is sited right in front of the window, so no shelves can be placed above the bench, but there are shelves either side of the window.

Regards,
Lloyd