GEC date codes

EC8010 · 23rd June 2003, 05:16 PM

Does anyone know how to crack the GEC date codes? I have reason to believe that "H" is before 1954, "L" before 1955, and "M" before 1957, and can contruct a table using those assumptions that might be right, but does anyone know the definitive answer?

fdegrove · 23rd June 2003, 09:14 PM

Hi,

Oh, dear...wish I could help you out on that one.

None of my books mention that manufacturers' dating code...Philips and associates, yes..but GEC?

Aren't there any company archives?
Maybe radio collectors or Hams could help you out...

Cheers and good luck,

316a · 23rd June 2003, 10:04 PM

Does this look correct ? This is what I've got written on the workshop wall

A = 1945
B = 1946
C = 1947
D = 1948
E = 1949
F = 1950
G = 1951...etc
L = 1955...etc
R = 1960...etc
Z = 1968

316a

EC8010 · 23rd June 2003, 10:34 PM

Yes. That's exactly what I've worked out! I worked out my codes by having some valves with BBC acceptance dates on them, but I had to do a few nudges to make them fit. I enabled this by assuming that the Beeb (mighty corporation although it is) could buy and accept valves a year or two after manufacture, they couldn't do so before...

So, my question is, where did your decoding come from? Did you do the same as me, or did you have a more concrete source?

316a · 23rd June 2003, 10:41 PM

I found them on the web somewhere with a fairly good list of factory codes such as KB/T , KB/F etc , if I find the URL I'll post it

316a

EC8010 · 23rd June 2003, 10:48 PM

So in that case, there's a good chance that the following is correct:

A 45
B 46
C 47
D 48
E 49
F 50
G 51
H 52
J 53
K 54
L 55
M 56
N 57
P 58
Q 59
R 60
S 61
T 62
U 63
V 64
W 65
X 66
Y 67
Z 68

I've not seen a GEC valve stamped 69, but I have one stamped 70.

Edit: Even better, this suggests that it was between 1961 and 1962 that GEC abandoned "smoked" in favour of "clear" glass KT66.

23rd June 2003, 05:16 PM	#1
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	GEC date codes Does anyone know how to crack the GEC date codes? I have reason to believe that "H" is before 1954, "L" before 1955, and "M" before 1957, and can contruct a table using those assumptions that might be right, but does anyone know the definitive answer? __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

23rd June 2003, 09:14 PM	#2
fdegrove diyAudio Senior Member Join Date: Aug 2002 Location: Belgium	Hi, Oh, dear...wish I could help you out on that one. None of my books mention that manufacturers' dating code...Philips and associates, yes..but GEC? Aren't there any company archives? Maybe radio collectors or Hams could help you out... Cheers and good luck, __________________ Frank

23rd June 2003, 10:04 PM	#3
316a diyAudio Member Join Date: Dec 2002 Location: West London	GEC codes Does this look correct ? This is what I've got written on the workshop wall A = 1945 B = 1946 C = 1947 D = 1948 E = 1949 F = 1950 G = 1951...etc L = 1955...etc R = 1960...etc Z = 1968 316a

23rd June 2003, 10:34 PM	#4
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	Eureka? Yes. That's exactly what I've worked out! I worked out my codes by having some valves with BBC acceptance dates on them, but I had to do a few nudges to make them fit. I enabled this by assuming that the Beeb (mighty corporation although it is) could buy and accept valves a year or two after manufacture, they couldn't do so before... So, my question is, where did your decoding come from? Did you do the same as me, or did you have a more concrete source? __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

23rd June 2003, 10:41 PM	#5
316a diyAudio Member Join Date: Dec 2002 Location: West London	Codes I found them on the web somewhere with a fairly good list of factory codes such as KB/T , KB/F etc , if I find the URL I'll post it 316a

23rd June 2003, 10:48 PM	#6
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	Brilliant! So in that case, there's a good chance that the following is correct: A 45 B 46 C 47 D 48 E 49 F 50 G 51 H 52 J 53 K 54 L 55 M 56 N 57 P 58 Q 59 R 60 S 61 T 62 U 63 V 64 W 65 X 66 Y 67 Z 68 I've not seen a GEC valve stamped 69, but I have one stamped 70. Edit: Even better, this suggests that it was between 1961 and 1962 that GEC abandoned "smoked" in favour of "clear" glass KT66. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

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