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Re: [Amps] High filament current on the 8877 amplifier tube

Subject: Re: [Amps] High filament current on the 8877 amplifier tube
From: Steve Thompson <>
Date: Mon, 16 Oct 2023 23:24:41 +0100
List-post: <>
Assuming they are Eimac manufacture, try asking CPI/Eimac for advice.

The only hazardous material in them is going to be the cathode coating
(Typ. Barium and Strontium oxides); radio and TV tubes containing the
same aren't normally considered hazardous.

Some years ago I used to get ceramic tubes cheap from the local scrap
metal dealer, where they were sent for the copper value in the anode.

Steve G8GSQ

On 16/10/2023 07:46, Tim Duffy 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"

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


Tim K3LR

From: Tim Duffy []
Sent: Sunday, October 8, 2023 2:48 PM
To: ''; ''
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?


Tim K3LR

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