A manufacturing defect is a lot different than operational failure of a good
tube. Eimac has had 3-500 defects also in the 80's
I believe both problems were due to the move of production from San Carlos
and poor QC.
Eimac also changed the 8877 spec around 79-80 to reduce gain. I have one of
those earlier "hot" tubes and it takes very little drive to bury a 2500W
slug even at 222 mHz.. Hams were blowing the grids with 100W exciters. Mine
was removed from an Alpha 77 at the customers request and replaced with the
new version, this was in the early 80's and it still puts out full and
stable power.
Carl
KM1H
----- Original Message -----
From: "Phil Clements" <philc@texascellnet.com>
To: <amps@contesting.com>
Sent: Monday, August 24, 2009 5:44 PM
Subject: Re: [Amps] parasitic oscillation techniques
> If you will recall, in the mid-1980's, there was a massive recall of all
> 8877's by Eimac. The explanation was that they had a "heat-dam" problem,
> whatever that is. An undetermined number of the defective tubes never made
> it back to the factory. They appeared at ham fests, and all over the
> internet sales sites. We had to go by the date codes on the tubes to
> protect
> ourselves. A trick by sellers was to remove the code from the tube.
>
> I will not bore you any further; many posts about this event are in the
> "Amps" archives, if you want more details.
>
> My guess is that hundreds, if not thousands, of 8877's were blown by
> customers prior to the recall, and factory and dealer stock had to be
> pulled
> and destroyed, or rebuilt.
>
> A thousand hams could not even come close to the loss to the Eimac 8877
> program, even if they had all built and botched amplifiers! The record for
> blowing 8877's is held by Eimac, and has not been broken since; even after
> 1988.
>
> (((73)))
> Phil, k5PC
>
>
>
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