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Old 13th December 2010, 06:06 AM   #1
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Default Question about coding on tube

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I have a set of tubes (see pictures):

The coding on the side of the tube is
GA0 B6L3
&
78-26

My translation of this is:

Tube Type: Ecc88 (code GA - this is correct)

Change Code 0

Made in Mullard, Blackburn factory (code B - this part confuses me because on the tube it says "Made in USA"

6L3 - Made in the 3rd week of December 1956 or 1966 - my understanding is that they changes over to the new coding system in 1956.......

Also, what does the 78-26 signify (this is in larger type white paint and the above listed code is in the typical hard to read really small type)

Last edited by maxseeley; 13th December 2010 at 06:11 AM.
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Old 13th December 2010, 11:18 AM   #2
DF96 is offline DF96  England
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I don't think the ECC88 had been invented in 1956, so it will be 1966. Also, as you imply, earlier date codes used 3 characters only.

Country of manufacture was often a pack of lies, so I am not at all surprised to find USA on something made in Britain.

Having said all that, the Philips code on these looks unusual: it is too large, upside down and appears to be paint rather than acid etch. So could these be later production, with a dodgy 'etch code' to increase their value? Are there any codes in faint brown near the bottom, right way up?
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Old 13th December 2010, 11:59 AM   #3
SY is offline SY  United States
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Interesting- I would have guessed 1978, 26th week.
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Old 13th December 2010, 12:20 PM   #4
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Quote:
Originally Posted by SY View Post
Interesting- I would have guessed 1978, 26th week.
same here.....
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Old 13th December 2010, 12:21 PM   #5
DF96 is offline DF96  England
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I am not an expert on these matters, but the getter in your valves looks like the later dish pattern. This would be consistent with a 1978 date, I think. Are these really late GA2, remarked as early GA0? Probably still fine valves, but not quite what they claim to be?

Can you check them? If they have been remarked then these is a slight risk that they are really ECC189 - the remote cutoff version. OK for phono input, but not line stages or phase spiltters.
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Old 13th December 2010, 12:43 PM   #6
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I know the tubes are authentic - they came from my work and the person who bought them (RIP) got them 30 to 40 years ago in bulk for equipment. He was EXTREMELY detail orientated and I don't think there was a lot of fake stuff going around back then. Plus, he would have bought them directly from HP.
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Old 13th December 2010, 12:47 PM   #7
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They are the later dimpled disk getters. Maybe I am reading the etched coding wrong - I will get out the magnifying glass.
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Old 13th December 2010, 12:59 PM   #8
SY is offline SY  United States
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Actually, it would have been just about 30 years ago that relabeled 6ES8 were being sold off in large quantities as ECC88. There's still plenty of those mislabeled tubes floating around; when I hear someone complain about the linearity of ECC88, I can be nearly certain that their experience is with one of those variable mu tubes.

Not that any of this matters- there are plenty of excellent ECC88 types available.
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Old 13th December 2010, 01:10 PM   #9
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from my scant tube lore knowledge, HP tubes were pretty much "cream of the crop". But the 70s were a strange time for tubes - these could be sourced from Britain, but that crosshatch pattern on the top almost looks Japanese.

If you're still curious, I can forward these pics to a friend of mine who is uh, a little obsessed with this type of rare knowledge.
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Old 13th December 2010, 01:37 PM   #10
DF96 is offline DF96  England
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The glass seams on the top more or less guarantee that the valves were made using Philips tooling, but not necessarily in a Philips-group factory as in the latter days they shipped it out to other places such as Ei (Serbia) or BEL (India). The dimpled-dish getter was most popular in the Dutch Heerlen factory, but appeared elsewhere too.
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