Date code stamps on Thorn tubes

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Paul
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Date code stamps on Thorn tubes

Postby Paul » Wed Jan 05, 2011 9:14 am

I understand that the dots etched on the Thorn tubes relate to the manufacture date? Can anyone confirm and if you happen to know how to decipher the series of dots, please let me know how to do the same! Thanks! ;)

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SuperSix
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Re: Date code stamps on Thorn tubes

Postby SuperSix » Wed Jan 05, 2011 7:21 pm

Well... I sort of know how it works but I've never had any success myself. I always get the dates wrong!

The date code is made of three groups dots and a dash in a line, normally at the bottom of the etch.

The first group which is a maximum of 5 dots gives you the year and dash meaning the first half of the factory year, no dash indicates the second half of the factory year.

5 Dots: 1979/84/89
4 Dots: 1980/85/90
3 Dots: 1981/86/91
2 Dots: 1982/87/92
1 Dot: 1983/88/93

It gets confusing though, Thorn starts its factory year in April so the second half of the factory year overruns into real calendar years.

The second group of dots gives the months, remember that the year half is indicated by the dash in the first group, a dash means the first half of the factory year.

6 Dots: April/October
5 Dots: May/November
4 Dots: June/December
3 Dots: July/January
2 Dots: August/February
1 Dot: September/March

The last group of dots gives the factory week.

4 Dots: First week of factory month
3 Dots: Second week
2 Dots: Third week
1 Dot: Fourth week
No Dots: Fifth week

You need to know what dates the etches are from too because there's several possibilities for each date code. I'm afraid I don't exactly know which etches where introduced when which is where I normally slip up. Either that or the fact that the year starts in April and the second half overruns into a new calendar year and I get confused.

Hope this helps!

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Paul
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Re: Date code stamps on Thorn tubes

Postby Paul » Wed Jan 05, 2011 8:55 pm

Thanks for the information! Certainly a lot more to it that I thought!
Hopefully now, I will at least be able to give it a try to decode the dots! 8-)

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sailormoon01uk
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Re: Date code stamps on Thorn tubes

Postby sailormoon01uk » Wed Feb 23, 2011 11:23 am

Thanks I can date my Thorn Fluorries and the 54w Filament Lamp

B.T.W some lamps have a Letter between the dots, according to James Hooker this is the Factory Code

All the Best

Colin

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Re: Date code stamps on Thorn tubes

Postby Tom » Sun May 15, 2011 3:12 pm

This should help with dating regarding the etch styles;

Small solo 'Thorn' on it's own - Late 70s through to around 1984-85, T8s had the iconic crown Thorn style caps

Bold 'THORN EMI' 1985 - 1988 Earlier T8s still had the crown caps which then became the modern plainT8 style

Bold 'THORN' on it's own with the EMI chopped off - 1988 through to around 1992 when all tubes were rebranded GE (sad day)

Well that's my guessing, hope this helps!
I LOVE LAMP!

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Re: Date code stamps on Thorn tubes

Postby Kev » Sat May 28, 2011 8:25 pm

According to lee it was 83 - 82 when the THORN EMI came out before that it was Thorn?


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