Re: High filament current on the 8877 amplifier tube
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And a "soft" tube acts as a soft fuse.
W4DNR? ? ? ? ??
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On 2023-10-16 10:35 am, Mike Sawyer via groups.io wrote:
I bought one off of Ebay once for about $30. The seller claimed it had low output. It didn't matter to me because at the time I was contemplating building an amp with one of them. My elmer Eric, WB4VVI(SK) always insisted on using a tube with low or no output to test the HV section and grid drive section. That way if you missed something during your construction and an 'event' happens during the testing phase, you will have ruined a tube of little value as opposed to a new or one with full output.
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Mod-U-Lator,
Mike(y)/W3SLK
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The duds could be eye candy for one's shack.? Maybe put them on QRZ, etc.
Andy? K9ATX
On 10/16/2023 1:46 AM, Tim Duffy K3LR wrote:
I am still testing 8877s here. Two or three every day. They warm up with filament only for 4 hours before HV.
What I have learned is that 8877's drawing 15 amps of filament current are bad tubes. They draw zero plate current.
So the five tubes that are high filament current ones, are "duds"
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So what is the proper way to dispose of these bad tubes?
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73
Tim K3LR
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Most 8877 tubes that I test draw 11 amps of filament current at 5 volts.
I have tested three recently that draw 15 amps of filament current. All of these tubes are used and have little "dings".
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Is 15 amps an indication of a problem tube? Or should I apply HV to the plate and see what happens?
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73
Tim K3LR
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"Where the Old Soo crossed the New Soo"
Duplainville, Wisconsin
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