CRM92 imploded in my store room,must see! - UK Vintage Radio Repair and Restoration Discussion Forum

oldeurope · 19th Oct 2005, 9:08 am

Good morning,
yesterday evening I went into my store room and fund a lot of glass
all over the floor.

The non emission CRM92 I stored there wasn't there
any more, only broken glass and the tube base.

Broken glass was all over the floor!
It stood right near the CRM93 in front of the WF cardbox.
I don't know why this tube imploded. I am happy that I wasen't there and
the CRM93 survieved. In the future I'll pack all tubes in boxes and use safety
glasses during handling them. These vintage tubes are really dangerous!
So take care!!!

Kind regards
Darius

Sideband · 19th Oct 2005, 10:19 am

Quote:

Originally Posted by Darius

I don't know why this tube imploded. I am happy that I wasen't there and
the CRM93 survieved. In the future I'll pack all tubes in boxes and use safety
glasses during handling them. These vintage tubes are really dangerous!
So take care!!!

Hi Darius. This serves as a warning to everyone who restores vintage televisions. Never take anything for granted and treat ALL vintage crt's (and any others) with the greatest of respect. It was probably a stress point that gave way. I'm told that glass becomes more brittle with age so there may be many potentially dangerous CRT's in working sets. I've seen some CRT's with air bubbles in the glass that have been there since manufacture and I think these could be very dangerous as the tubes get older.

Just glad that you were not there when it went!

Best regards and TAKE CARE.

Rich.

Sideband · 19th Oct 2005, 2:52 pm

Quote:

Originally Posted by Darius

Maybe temperature changes in the room caused this?
I don't know. Why is it so much destroyed? The other broken tube in the
set I got from ebay was broken in three pieces and not a thausend pieces
of glass. It is unbeleveable!

You have a good point Darius. Probably correct about the temperature changes although I would think a SUDDEN change was more likely to cause damage rather than a gentle cooling overnight. Who can tell? If there was a stress point in the bowl of the tube, this could have failed during a cooling period. Stress in the bowl is more likely to have caused the total destruction as the sides would have collapsed inwards. If it had been at the neck, probably just a crack and a hiss! Was this the tube you had from eBay? Possibly transportation had weakened it at some point on the bowl or maybe even a deep scratch had started it.

At any rate, the most important thing is you are OK and can still entertain us with your projects and restorations.

Rich.

Panrock · 19th Oct 2005, 6:25 pm

Wow!!

Glad you're Okay...

One thing I'm always wary of is leaving tubes where a glint of sunlight can catch them through a window. As the sun moves round the sky this can happen without warning while you're doing something else. It can cause local heating.

At the moment I'm moving my pre-war Emiscope 6/6 in and out of the set quite a lot as I do the final troubleshooting. It has relatively heavy iron laminations sitting around the scan coils and I try not to strain the neck as I turn it round to up-end it - but you never know...

I'm wearing my goggles just in case.

Steve

Heatercathodeshort · 19th Oct 2005, 7:25 pm

Hello Darius,
Sorry to see the remains of your CRM92. I have mentioned before the stress factor of old glass and I wont waste web space mentioning again but I think we should not panic over this. The MAZDA range of triode tubes were very thin and light. Handling the 15" CRM151 is a truly frightening experience. You will find air bubbles in some vintage tubes. The bulbs were blown by hand one at a time believe it or not! This was common before the faceplate was made as a seperate item and then glass ' welded' to the cone.
I doubt very much if the air bubble would weaken the tube. As mentioned by Richard and others, the implosion was almost certainly caused by shock encountered with all the transportation and handling. This together with the overnight temperature change led to the collapse of the envelope.
The CRM series are not PYREX. As far as I know from my regun days EMI were the only tube makers to use this type of glass. PYREX is very hard but subjected to EXTREME RAPID temperature changes can explode into tiny fragments similar to the old car windscreens. Too boring for this thread but I was once in a kitchen where a PYREX dish did just that! I think the old pre war tubes are safe due to their thickness!
I would certainly wear eye protection when handling any tube that is not fitted with a RIMBAND. These first appeared in 1964 and are little changed from todays production. There were other methods of implosion protection such as the TWIN PANEL but these are rare today.
Caution is required but not a panic outbreak...Regards. JOHN.

Nickthedentist · 20th Oct 2005, 11:37 am

Quote:

Originally Posted by Booby

Had the tube travelled in an aircraft at some time?

The place I worked at would always buy a seat on an aircraft for a vacuum tube we delt with, as they would crack sometime later after being in the low pressure luggage hold.

I've certainly transported several MODERN TVs in the baggae hold on aircraft, with no problems...yet

But from Darius' pictures, the glass used on these vintage ones seems much thinner.

Nick.

ppppenguin · 20th Oct 2005, 11:43 am

The cabin and luggage hold are at the same pressure. The only reason to give a tube a seat on an aircraft is to prevent it being bounced around by the baggage handlers. Now that's a challenge to any packaging!

Early tubes certainly had thinner faceplates. I don't know if there are any aging mechanisms in the glass. I've often heard it said that window glass gets older it becomes more difficult to cut cleanly.

SPCh · 20th Oct 2005, 11:57 am

Glass remains plastic indefinitely, and flows with gravity. That's why the pieces in a mediaeval stained glass window are thicker at the bottom than at the top. It could also explain the difficulty with cutting old glass, but I don't see why it should make implosions more probable or more dramatic.

ppppenguin · 20th Oct 2005, 5:04 pm

Unless I have special packing, I usually store CRTs on their faceplates. Preferably on a soft surface. Maybe I should review this, especially for older tubes. As for handling tubes, I reckon that familiarity breeds contempt. I was at Display Electronics (the tube rebuilders at Uxbridge, presumably no longer in business) and the owner picked up a heavy modern 24" monochrome CRT by the neck and carried it around quite casually. I had to restrain myself from hiding in a safe place.

Regarding transport of vacuum tubes by air I would cite this item from American Airlines. I have found similar material on other airline web sites.

http://www.aacargo.com/shipping/animals.jhtml

"Aircraft Travel Compartment Information
Animals are transported in the same compartments as baggage, mail and other cargo. These compartments are pressurized and maintain a temperature range from 50-70 degrees Fahrenheit"

As a warning to all northerners in the forum I also found the following warning on the same web page

"Ferrets are not accepted to or from California or Puerto Rico, except for research purposes. A special permit is required."

19th Oct 2005, 9:08 am	#1
oldeurope Retired Dormant Member Join Date: Dec 2003 Location: Solingen, Germany Posts: 727	CRM92 imploded in my store room,must see! Good morning, yesterday evening I went into my store room and fund a lot of glass all over the floor. The non emission CRM92 I stored there wasn't there any more, only broken glass and the tube base. Broken glass was all over the floor! It stood right near the CRM93 in front of the WF cardbox. I don't know why this tube imploded. I am happy that I wasen't there and the CRM93 survieved. In the future I'll pack all tubes in boxes and use safety glasses during handling them. These vintage tubes are really dangerous! So take care!!! Kind regards Darius Attached Thumbnails

19th Oct 2005, 6:25 pm	#4
Panrock Nonode Join Date: Feb 2005 Location: Worcestershire, UK. Posts: 2,533	Re: CRM92 imploded in my store room,must see! Wow!! Glad you're Okay... One thing I'm always wary of is leaving tubes where a glint of sunlight can catch them through a window. As the sun moves round the sky this can happen without warning while you're doing something else. It can cause local heating. At the moment I'm moving my pre-war Emiscope 6/6 in and out of the set quite a lot as I do the final troubleshooting. It has relatively heavy iron laminations sitting around the scan coils and I try not to strain the neck as I turn it round to up-end it - but you never know... I'm wearing my goggles just in case. Steve

19th Oct 2005, 7:25 pm	#5
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: CRM92 imploded in my store room,must see! Hello Darius, Sorry to see the remains of your CRM92. I have mentioned before the stress factor of old glass and I wont waste web space mentioning again but I think we should not panic over this. The MAZDA range of triode tubes were very thin and light. Handling the 15" CRM151 is a truly frightening experience. You will find air bubbles in some vintage tubes. The bulbs were blown by hand one at a time believe it or not! This was common before the faceplate was made as a seperate item and then glass ' welded' to the cone. I doubt very much if the air bubble would weaken the tube. As mentioned by Richard and others, the implosion was almost certainly caused by shock encountered with all the transportation and handling. This together with the overnight temperature change led to the collapse of the envelope. The CRM series are not PYREX. As far as I know from my regun days EMI were the only tube makers to use this type of glass. PYREX is very hard but subjected to EXTREME RAPID temperature changes can explode into tiny fragments similar to the old car windscreens. Too boring for this thread but I was once in a kitchen where a PYREX dish did just that! I think the old pre war tubes are safe due to their thickness! I would certainly wear eye protection when handling any tube that is not fitted with a RIMBAND. These first appeared in 1964 and are little changed from todays production. There were other methods of implosion protection such as the TWIN PANEL but these are rare today. Caution is required but not a panic outbreak...Regards. JOHN.

20th Oct 2005, 11:43 am	#7
ppppenguin Retired Dormant Member Join Date: Dec 2003 Location: North London, UK. Posts: 6,168	Re: CRM92 imploded in my store room,must see! The cabin and luggage hold are at the same pressure. The only reason to give a tube a seat on an aircraft is to prevent it being bounced around by the baggage handlers. Now that's a challenge to any packaging! Early tubes certainly had thinner faceplates. I don't know if there are any aging mechanisms in the glass. I've often heard it said that window glass gets older it becomes more difficult to cut cleanly.

20th Oct 2005, 11:57 am	#8
SPCh Rest in Peace Join Date: Nov 2004 Location: Antwerp, Belgium Posts: 345	Re: CRM92 imploded in my store room,must see! Glass remains plastic indefinitely, and flows with gravity. That's why the pieces in a mediaeval stained glass window are thicker at the bottom than at the top. It could also explain the difficulty with cutting old glass, but I don't see why it should make implosions more probable or more dramatic.

20th Oct 2005, 5:04 pm	#9
ppppenguin Retired Dormant Member Join Date: Dec 2003 Location: North London, UK. Posts: 6,168	Re: CRM92 imploded in my store room,must see! Unless I have special packing, I usually store CRTs on their faceplates. Preferably on a soft surface. Maybe I should review this, especially for older tubes. As for handling tubes, I reckon that familiarity breeds contempt. I was at Display Electronics (the tube rebuilders at Uxbridge, presumably no longer in business) and the owner picked up a heavy modern 24" monochrome CRT by the neck and carried it around quite casually. I had to restrain myself from hiding in a safe place. Regarding transport of vacuum tubes by air I would cite this item from American Airlines. I have found similar material on other airline web sites. http://www.aacargo.com/shipping/animals.jhtml "Aircraft Travel Compartment Information Animals are transported in the same compartments as baggage, mail and other cargo. These compartments are pressurized and maintain a temperature range from 50-70 degrees Fahrenheit" As a warning to all northerners in the forum I also found the following warning on the same web page "Ferrets are not accepted to or from California or Puerto Rico, except for research purposes. A special permit is required."