Thorn made. Must of lost vacuum. No surprises there then lol. Thorn tubes are shit

Yup. Got another one like this but Thorn branded, exactly the same broken cathode and lost vacuum. They're both on the scrap tube pile now.

Shame its dead. Don't think i've seen a Thorn made GEC like this before.

Thorn tubes seem to have a shelf life in my expierience. The seals just fail after a while. I’m guessing there’s absolutely no signs of any damage? Last time I tested my tubes a load of my thorns were dead or seals had failed. And they’d only just been sitting there!

I read somewhere that the copper leads corrode that pass through the glass and it breaks the seal, and that Thorn's were prone to it due to poor quality copper used. No idea if that's fact or theory, but sounds plausible, especially as this one has been sat in a damp workshop unused for 20 years.

Nice oldie...Shame its dud!

sounds completely plausible. That was what I always wondered might be the cause.

It’s a friggin shame though coz this one is a really nice one! It’s annoying as it is always the “nicest” ones

Wasn't the lead wires in the seal made from niobium or something like that so it has the same thermal expansion as the glass? I'd be tempted to smash it up and have a look at the internal construction.

Yeh its called 'dumet' wire, its a nickel/iron alloy cored wire with a copper layer on the outside, with the copper being about 30% of the total mass. It has to be prepared by oxidising the surface before sealing it into a tube otherwise it wont wet the glass and will eventually leak or crack the pinch. Bubbles can also form around this seal and if they are near enough to the inside of the tube, they can chip out of the glass and contaminate the lamp if its exposed to large or sudden temperature swings, especially running it for a short time after its been in the cold with the cathode heat conducting down it, as dan found out with his ascot tubes from eveready.

Ive been told a healthy dumet seal should be the same colour as red wine, if it looks coppery its bad.

That's very interesting, thanks for the info. I'll smash the end off and have a look sometime

I lost 6 of the Ascot tubes for this sadly. Lit them too soon and they were still stone cold through. At least I’ve still got 9 good ones lol. Although the other 6 would of been nice too!

What a gem shame this is EOL!

thorn tubes are shit danny? thought they were some of the old time greats? age can play a part on failing if kept in poor conditions i guess

Personally, I like Thorn tubes - a great bit of British history. It's a shame tho that they do seem a little less robust than some tubes are when they age. I've had 3 40w Kolorite tubes either lose vacuum or ring off, which is a shame as I only purchased 3 in the first place. Touch wood tho, they do seem to be the only ones. Maybe a bad batch / stored somewhere damp / subject to some sort of stress or abuse somewhere in the 30 odd yrs since they were made. Who knows?

I now have a gec 125w warm white with brass end caps

Based on my experience of lamp bin raiding etc, Thorn/Atlas/BLI/TEI (pick any) tubes are less robust than some other manufactures. I've previously seen (and currently own) a few GB Philips tubes that have obviously been bashed around and abused but still work fine. I've seen Thorn tubes still in cardboard sleeves that haven't been used suffer from cracked/fallen off ends. Not really scientific testing, just my observations.

This tube is now being made into a Crompton LED tube ....possibly. It went to the recycle bin anyway!