To: <amps@contesting.com>
> Date: Thu, 21 May 1998 09:17:14 +0100
> From: Peter Chadwick <Peter_Chadwick@mitel.com>
Hi Peter,
> - No, the tube. All tubes are not equal, even from the same manufacturer's
> batch. Not using a parasitic suppressor may be OK in an HF amp, but for
> reliability and repeatability, I wouldn't do it. Not even on a 'one off' for
> myself.
Two questions.
Exactly how much change do you see in a tube. Let's take an 8877 for
example? What parameters change so drastically?
> >I've seen a melt through in may inadequately cooled tubes. How do you
> >know it was a parasitic? Did you ever calculate current required to
> >heat the glass with RF heating?
>
> In the cases I saw, it was during development, the amplifiers was suffering
> very badly with parasitics, and in the 572 case, the lead running near the
> glass discoloured. It also happened pretty quickly - the plates hadn't got
> bright red. What else was likely?
Two more questions. How did you know the amps had parasitics?
What lead running near the glass?
73, Tom W8JI
w8ji.tom@MCIONE.com
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