[Amps] High filament current on the 8877 amplifier tube

[Tim Duffy]

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"

 

So what is the proper way to dispose of these bad tubes?

 

73

Tim K3LR

 

From: Tim Duffy [mailto:k3lr at k3lr.com] 
Sent: Sunday, October 8, 2023 2:48 PM
To: 'ham-amplifiers at groups.io'; 'amps at contesting.com'
Subject: High filament current on the 8877 amplifier tube

 

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".

 

Is 15 amps an indication of a problem tube? Or should I apply HV to the
plate and see what happens?

 

73

Tim K3LR