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Old 8th July 2004, 08:45 PM   #1
hifiZen is offline hifiZen  Canada
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Default Amperex 6DJ8

Some time ago, I acquired (for free ) a handful Amperex 6DJ8 in very good condition (slightly used... I'll get 'em in a tester eventually). These sat in a box for several years, but expecting to use them in some upcoming projects, I dug them out and started checking around to see what's available in the way of substitutions / replacements. Then I discovered these Amperex tubes are selling for $90 NOS or more ... I guess I'll just reserve these for those extra-special listening sessions, and buy some cheaper ones for testing and casual listening. Anyone have suggestions for good, cheap 6DJ8/6922s? Are the Sovteks any good?

Anyway, what is it that makes the Amperex tubes so special? Do they really sound that good, or are they just getting rare? ... Are collectors hoarding them? According to this page, there are several types of Amperex 6DJ8. The ones I have are orange globe label, made in Holland, but I'm not sure if they're 'A-Frame' types or not. How do I tell?

OK let me take a picture (gee I love digital cameras)... The ones I've got have either a dimpled solid round getter or a circular getter.

Finally, does anyone know where I can get some info about the production codes?
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Old 9th July 2004, 01:33 AM   #2
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Default FOR 90 BUCKS....

Hi,

Quote:
Finally, does anyone know where I can get some info about the production codes?
If you could give the code. It's acid etched right above the glass stem.

Quote:
Anyone have suggestions for good, cheap 6DJ8/6922s? Are the Sovteks any good?
Cryoed JJ ECC88s are among the best.
Sovtek 6922 are technically O.K. but soundwize there's no match for good NOS ECC88s like 1960 era Mullard or Philips.

Cheers,
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Old 9th July 2004, 02:06 AM   #3
hifiZen is offline hifiZen  Canada
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Well, this helped a fair bit. At least I know what A-Frame construction is now.

Now this is interesting... here's where I found that $90 tube. But if you look carefully at the enlarged photo, it appears to be a counterfeit!

Thanks for the tip on the Cryo JJ's. I'll seek out a few of those. I've had good experience with JJ tubes in the past.

Anyway, about the lot codes... they don't appear to be acid etched but rather printed in a dark ink. They consist of two lines, which all read GAC on the first line. The second lines contain the following codes:

47H1
49C1 - (three tubes)
49C2
49B1
4712 - hard to read this one, the 1 could be an I

There is also another set of codes printed vertically in orange at the end of the logo, and are as follows (tubes in the same order):

746
919
926
9?6 - illegible... 1 or 2 maybe.
920
917
820

...and of course, there are also a few numerals embossed on the inside of the glass base, but I'm pretty sure those aren't lot codes.

Thanks.
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Old 9th July 2004, 02:53 AM   #4
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Hi,

Quote:
Well, this helped a fair bit. At least I know what A-Frame construction is now.
Yeah....the rest is not something I'd like to read in a book about tube history as it's mostly incorrect yet given as fact anyway...
Anyone could make a list of all the items that are total nonsense on those pages but it could soon become a full-time job, so ....

Quote:
But if you look carefully at the enlarged photo, it appears to be a counterfeit!
Not necessarily counterfeit but rather unclear about its origins.
Unless you actually hold one in your hands for closer inspection it's hard to say what it is....
90$, huh? Not in my lifetime....

As for the codes: GAC (Type, Type, Batch) GA = ECC88 Batch: C = 1953?

I'll try to look into the rest of them tomorrow but at first sight they do seem genuine Philips codes.

Quote:
they don't appear to be acid etched but rather printed in a dark ink.
Rest assured it's NOT ink....so it can't be removed as far as I know. Not unless you'd want to risk damaging the glass anyway.

Cheers,
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Old 9th July 2004, 09:11 AM   #5
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Default Re: Amperex 6DJ8

Quote:
Originally posted by hifiZen
Some time ago, I acquired (for free ) a handful Amperex 6DJ8 in very good condition

Hello ,

'47H1 , 49C1 , 49C2 , 49B1 , 4712'

The '4' is more than likely a '/|' (delta) which is the factory code for Philips , Herleen , Netherlands .
If the valves have 'A' frame getter supports and dimpled disc getters , these will be of 1970's manufacture (1977 and 1979) and should have 'GA2' type codes . With all the so called 'fake' 6922/ECC88 around , you're probably better off with used ones pulled from a Tek scope . You would not believe what some major UK valve dealers are doing at present with 7DJ8 (PCC88) . Someone must have found several thousand of these ! These valves are being washed and having very dodgy looking Mullard logo's added then placing a sticker that says 'ECC88' over where it should say 'PCC88' , some also have had their pins gold plated being touted as CV2493/E88CC-01 . Can be easily spotted by the codes , which of course are incorrect for a ECC88 . These will work but will not work optimally and are popping up in dealers all over the USA and the far east , naughty , naughty and very expensive for what the things are . Know the codes and avoid getting fleeced

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Old 9th July 2004, 10:36 AM   #6
hifiZen is offline hifiZen  Canada
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These were indeed pulled from a Tek scope! I got the scope for free, and used it to measure some of my first DIY circuits. But there's only so much you can do with 500kHz bandwidth, and only so far I'm willing to haul one of those old clunkers. So, it got boxed up and shoved in the corner of a relative's garage, where it sat for years. I recently contracted the tube fever again, and remembering the old scope, I decided to see if there was something useful inside it that would help cure my ailment... Well, visiting family never felt so good! I harvested 7 Amperex + 1 GE 6DJ8, along with a pair of Mullard 6BL8s, 2x GE 6AU6, and a handful of other tubes: 7119, 7233, 12BH7A, 6CZ5, 6AS7G, 0G3 and a 6BJ7. While I was yanking tubes, I had my eye on that Tek power transformer too... Hmm... I wonder what I could build with that?

Anyway, I have no doubts about their authenticity. I'm still floored by the price of these tubes - I had no idea these Amperex 6DJ8s were so expensive now.

On closer inspection, I think you're right about the 4 being a delta. None of these are A-frames, though.
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Old 9th July 2004, 11:53 AM   #7
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Default Tek Scopes

Quote:
Originally posted by hifiZen
These were indeed pulled from a Tek scope! I got the scope for free, and used it to measure some of my first DIY circuits. But there's only so much you can do with 500kHz bandwidth, and only so far I'm willing to haul one of those old clunkers. So, it got boxed up and shoved in the corner of a relative's garage, where it sat for years. I recently contracted the tube fever again, and remembering the old scope, I decided to see if there was something useful inside it that would help cure my ailment... Well, visiting family never felt so good! I harvested 7 Amperex + 1 GE 6DJ8, along with a pair of Mullard 6BL8s, 2x GE 6AU6, and a handful of other tubes: 7119, 7233, 12BH7A, 6CZ5, 6AS7G, 0G3 and a 6BJ7. While I was yanking tubes, I had my eye on that Tek power transformer too... Hmm... I wonder what I could build with that?

Anyway, I have no doubts about their authenticity. I'm still floored by the price of these tubes - I had no idea these Amperex 6DJ8s were so expensive now.

On closer inspection, I think you're right about the 4 being a delta. None of these are A-frames, though.
Hello ,
Sounds like you broke up a Tek 5xx series . The power transformers usually have many heater windings , same with HT and look super chunky . Get the ECC88 tested , I find that those that test well over the minimum limit but under 100% (12.5mA/V) at 10mA/V can be noisy but no doubt you'll get a few good ones from what you have got . Ring gettered Herleen ECC88 will be from the 1960's with those codes

ps Don't forget to salvage the ceramic tagstrips from the scope

cheers

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Old 10th July 2004, 04:29 AM   #8
hifiZen is offline hifiZen  Canada
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Yep, it was a 564 'storage' scope, with 3A3 dual diff amp (kinda nice) and 2B67 timebase. All in all, a nice little starter scope, and I'm sure it was pretty expensive in it's day. Very, very nicely built, too. I didn't have time to do any real disassembly, so it's back in it's box, minus tubes. Eventually I'll make another trip to retrieve it, and then I'll harvest all the other parts which require disassembly.

Any idea where I can find data on the transformer? It's a Tek model 120-0296-00.
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Old 10th July 2004, 09:13 AM   #9
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Default Scope

Quote:
Originally posted by hifiZen

Any idea where I can find data on the transformer? It's a Tek model 120-0296-00.
Hello ,
I have a few Tek manuals , I'll take a look and let you know

cheers

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