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Old 14th June 2011, 04:18 PM   #1
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Question Trying to identify an old radio tube

This may be an impossible task, but I'm trying to identify an old tube. Here's the deal... I bought this homemade amp that looks like it was built using transformers and some caps from an early 50s RCA radio perhaps. It has a 25L6GT and a 6AV6... and 3 small unidentified tubes. There's a bit of writing left on one and it looks like it may have said something like 6AK5W... but the A is the only firmly legible thing. First number may be a 3 or 8. Is there any way to guess what they may be? The person I bought it from suggested 6AH5... but I don't know if that was an educated guess or just an attempt to read it. Thanks for any help...

Mark.

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Old 14th June 2011, 04:28 PM   #2
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This is 6AK5 (EF95) or 18AK5. You have to measure the heating voltage to tell which of the 2 it is.
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Old 14th June 2011, 05:08 PM   #3
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Quote:
it may have said something like 6AK5W
Thats what it looks like to me. I have never seen an 18AK5, but I had about 5000 6AK5's. Gave most away.
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Old 14th June 2011, 08:45 PM   #4
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Ah cool thanks - can't believe I actually read it right... xray vision activated.

Mark.
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Old 15th June 2011, 01:16 AM   #5
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I will place a bet on a 18AK5W, because it you said it's from a series-string radio and because the first digit looks like the remains of an 8.
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Old 15th June 2011, 02:05 AM   #6
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I will place a bet on a 18AK5W, because it you said it's from a series-string radio and because the first digit looks like the remains of an 8.
18AK5 draws 50 mA. 25L6 and 6AV6 draw 300 mA. They can't be in series.

Assuming the original tube has a good heater feed it 6 volts and see if it lights up.

The tube has the guts of a 6AK5 or a 18AK5 which was very uncommon in the US. The only evidence that they exist comes from Germany and the tubes were Siemens. There are a few other tubes that look the same 6AS6 and 6AJ5 come to mind. The 6AH5 is a large octal tube, also quite rare.
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Old 15th June 2011, 04:01 AM   #7
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AFAIR, 6AK5 draws 175 mA.
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Old 15th June 2011, 06:47 AM   #8
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Quote:
Originally Posted by tubelab.com View Post
I had about 5000 6AK5's. Gave most away.
I gave mine to my girlfriend to turn into necklaces

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