>Subject: Re: [AMPS] good, bad, ugly
>Sent: 3/26/1997 1:14 PM
>Received: 3/26/1997 12:46 PM
>From: Garry & Yelena, ni6t@scruznet.com
>To: Rich Measures, measures@vc.net
>
>Rich Measures wrote:
>>.
>>
>> RE: the 80 series Alpha amplifiers: Sure, the warranty is
>> superb---however, at least a third of the owners that I talked to have
>> had sudden, unexplained failures during the warranty period. IMO, this
>> rate of return is a bit too high, Dick.
>>
>> R. L. Measures, [805]386-3734
>
>I lugged an Alpha 91 prototype, provided by the factory, to Conway Reef
>in March, 1995, where it failed. It was of course shipped back to the
>factory when it got back here. Since no info was forthcoming, I called
>several times to find out what had happened. The ETO design was, of
>course, grid-driven, but used cathode degeneration, which then consisted
>of 5 resistors in parallel. One had gone, they said, which stressed the
>others, which went in turn. They also said they had changed the type of
>resistor used, when they went to production.
>
>I should not have allowed myself to be a guinea pig.
>--
What was the rating of the 5 cathode RF negative feedback resistors,
Garry? I wonder how Alpha would have known that one resistor initially
failed by itself--as opposed to a simultaneous failure of the 5? The one
resistor failed story sounds like an attempt to blame the failure on a
defective resistor instead of elsewhere--i.e., Not Invented Here
Syndrome.
Is the model 91 amplifier neutralized? Is an inductor connected in
series with the grid termination R? What is the value of the grid
termination R? Is the screen voltage regulated by a pass regulator or a
shunt regulator?
R. L. Measures, [805]386-3734
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