TT Re: [TenTec] Ten Tec amps and ALC

[Tommy]

A word of caution about ALC....do not EVER think ALC completely protects the
grids of your amps tubes. The 'little' problem that ALC has is that it is
slow. Most radios that use ALC for controlling output power level,  produce
a very short (microseconds), high level RF spike, until the ALC circuit can
grab hold of it and bring it back down to a 'regulated' level. More that one
pair of 3cx800a7's have mysteriously failed, and investigation showed the
HUGE RF spike (300-500 watts) present on the leading edge of the RF waveform
going to the amp, be it SSB, digital, or CW. If you want to be sure, check
your xmtr's RF output waveform with a scope, running at about 10
microseconds per division. Otherwise just replace expensive grid driven
tubes, which seem to fail for no apparent reason. The Eimac suggested
replacement, 3cpx800a7, is supposed to be more rugged in this
respect....just in case one would need new  tubes.

Tom - W4BQF

----- Original Message -----
From: "Stuart Rohre" <rohre at arlut.utexas.edu>
To: <tentec at contesting.com>
Sent: Wednesday, August 18, 2004 6:37 PM
Subject: TT Re: [TenTec] Ten Tec amps and ALC


> An overdrive indicator on an amplifier seems an excellent feature, to
avoid
> the possible non-compatibility of ALC circuits in light of no universal
ALC
> standard.
> -Stuart
> K5KVH
>
>
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