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 Post subject: Unknown Tube Type (Pictured)
PostPosted: Jun Sat 15, 2019 4:09 pm 
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I have four of the below pictured tubes in my ST-70 Clone where my other ST-70 has 6CA7s installed. Does anyone recognize the tube type (all that is marked on the tube is the number 42, nothing else)?

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TIA,

Terry


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 Post subject: Re: Unknown Tube Type (Pictured)
PostPosted: Jun Sat 15, 2019 9:38 pm 
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That may well be a 6AC7 though l've seen only metal versions. Does it test as a 6AC7? Craig


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 Post subject: Re: Unknown Tube Type (Pictured)
PostPosted: Jun Sat 15, 2019 9:59 pm 
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Certainly looks like an EL34 which could also be a 6CA7.

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 Post subject: Re: Unknown Tube Type (Pictured)
PostPosted: Jun Sun 16, 2019 12:01 am 
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I haven't tested them yet, since I wasn't sure of the tube type. What do you suppose the 42 is for/means?


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 Post subject: Re: Unknown Tube Type (Pictured)
PostPosted: Jun Sun 16, 2019 12:31 pm 
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radioterry wrote:
...What do you suppose the 42 is for/means?

Something related to production/manufacturing. It could be a date code, a plant code, sequence code or whatever. But you should be able to carefully look inside and see what pins connect to which elements and then determine if it is an EL34.

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 Post subject: Re: Unknown Tube Type (Pictured)
PostPosted: Jun Sun 16, 2019 1:51 pm 
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I'm thinking the tube is an EL34 most likely a later eastern European tube. Harry


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 Post subject: Re: Unknown Tube Type (Pictured)
PostPosted: Jun Sun 16, 2019 4:54 pm 
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OK, they all tested strong as a 6CA7 on my C.G. Industries calibrated and upgraded Heathkit TT1A.

Terry


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 Post subject: Re: Unknown Tube Type (Pictured)
PostPosted: Jun Mon 17, 2019 11:51 am 
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They might be Russian made. Try and contact our resident tube expert Jim Cross. Also if you use FB this is a good group https://www.facebook.com/groups/249201115164268/


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 Post subject: Re: Unknown Tube Type (Pictured)
PostPosted: Jun Mon 17, 2019 3:31 pm 
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These look like Eastern European EL34s to me.


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 Post subject: Re: Unknown Tube Type (Pictured)
PostPosted: Jun Mon 17, 2019 8:02 pm 
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Jim Cross wrote:
These look like Eastern European EL34s to me.

Thanks, Jim.

What do you suppose the 42 on them signifies? I wonder if it the max screen bias voltage rating?


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 Post subject: Re: Unknown Tube Type (Pictured)
PostPosted: Jun Mon 17, 2019 11:16 pm 
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radioterry wrote:
Jim Cross wrote:
These look like Eastern European EL34s to me.

Thanks, Jim.

What do you suppose the 42 on them signifies? I wonder if it the max screen bias voltage rating?


Very doubtful that the 42 means screen bias...

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 Post subject: Re: Unknown Tube Type (Pictured)
PostPosted: Jun Tue 18, 2019 12:23 am 
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Don Cavey wrote:
radioterry wrote:
Jim Cross wrote:
These look like Eastern European EL34s to me.

Thanks, Jim.

What do you suppose the 42 on them signifies? I wonder if it the max screen bias voltage rating?


Very doubtful that the 42 means screen bias...

Why? 42 is the max screen bias voltage on a EL34/6CA7. There is no other 42 that I can associate with this type tube.


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 Post subject: Re: Unknown Tube Type (Pictured)
PostPosted: Jun Tue 18, 2019 12:03 pm 
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uhhh..... 42 is the answer to "the question" what is the meaning of Life, The Universe, and Everything. Duh!! That is one SPECIAL tube ya got there. :-D

For those still puzzled, google "hitchhikers guide to the galaxy"

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