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 Post subject: Heater-Cathode Leakage
PostPosted: Feb Wed 14, 2018 11:55 pm 
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Joined: Aug Tue 10, 2010 3:36 am
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Location: Lake Winola, PA
How much Heater-Cathode leakage is tolerable or acceptable in the 6V6GT or 6L6GC. My EICO yields these results in Megohms.....for example 20 Megs, 10 Megs or 5 Megs....right on the meter. Thanks....


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 Post subject: Re: Heater-Cathode Leakage
PostPosted: Feb Thu 15, 2018 1:59 am 
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Joined: Jun Sat 09, 2007 8:14 am
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Location: Florida
This made me curious so I did something strange. I looked up heater-to-cathode leakage in the Langford-Smith Radiotron book. The test [3.3ii(d)] called out application of max specified heater/cathode voltage and looking for a leakage current of 20ua or less. Exactly how this applies to your EICO (which one?) only EICO knows.

RRM


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 Post subject: Re: Heater-Cathode Leakage
PostPosted: Feb Thu 15, 2018 2:19 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: San Jose, CA USA
It's completely circuit dependent. A 6V6 or 6L6 is likely to be used only in a fairly high current output stage. Both would be used mainly in transformer sets, so the heater-cathode voltage won't be much. The combination of these two things means that these two tubes are not very sensitive to heater-cathode leakage. One could do an experiment by intentionally connecting a resistor between heater and cathode and seeing what happens.

Once you get into mA of heater-cathode leakage, you might hear so hum in an output tube, but below that I'm guessing you can't.

_________________
Tom K6VL


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 Post subject: Re: Heater-Cathode Leakage
PostPosted: Feb Thu 15, 2018 2:22 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Mpls, Minnesota
Page 6 third paragraph of the 667 manual gives you the allowable leakage.

Dave


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 Post subject: Re: Heater-Cathode Leakage
PostPosted: Feb Thu 15, 2018 2:28 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 437
Location: Monte Vista, CO. USA
The Hickok Cardmatic tests uses a leakage reject current of 50uA for the 6V6, the 6L6 is 70uA.


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 Post subject: Re: Heater-Cathode Leakage
PostPosted: Feb Thu 15, 2018 6:38 pm 
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Joined: Aug Tue 10, 2010 3:36 am
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Location: Lake Winola, PA
Dave, thanks! I will look for that page of the 667 paperwork.


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