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[Amps] Tube Glow 101

To: <>
Subject: [Amps] Tube Glow 101
From: "Mark Beckwith" <>
Date: Tue, 10 Jul 2007 09:17:41 -0500
List-post: <>
> Hi Mark,
> The only significant thing that makes the anode glow red is power 
> dissipation in the anode.

Thanks Tom, for taking the time to write this helpful long explanation (most 
of which is not included in this response).  I understand there's more to it 
than I thought, and you managed to increase my understanding albeit over 
several days of digesting your note!

In a nutshell could one say that a design goal to minimize 4-1000 wear and 
tear would be to engineer the deck to maximize efficiency?  I never thought 
of it this way and it would make a difference in my approach (all you guys 
rolling your eyes and saying "duh" could you just delete this email and move 
on?  Thanks).

So overdrive is under control because I only operate CW, I watch the grid 
drive, and I'm using a 4-1000.  Got it.  I won't cook any grids.

> If I mistune an amplifier with excessively light loading (too much 
> capacitance for the power) the loadline is much too high an impedance.

So once and for all, in non-EE terms, as "loading C" goes DOWN, "loading" is 
said to go UP, right?  Is this some kind of secret code so EEs can retain 
their mystique?  Can you help me understand why it is not what seems 
obvious - as "loading C" goes up "loading" goes up?

> On the other hand a tube like the 3CX800 or 3CX1500 can be ruined with 
> only seconds of excessive grid current

Hence the 4-1000 project :)  Those fancy tubes are too expensive and risky 
for such a dunderhead as myself.

My commercial amp I use day-to-day is an Alpha 86.  It has 3CX800s in it. 
It has a lot of fancy automatic tripping circuitry which I try to invoke as 
little as possible.  I know it trips under an excessive reflected power 
condition.  Does it also trip under an excessive grid current condition?  Am 
I relatively safe from this particular stupid mistake?

Thanks for holding my hand on this one.

Mark, N5OT 

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