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[AMPS] glitch resistors

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Subject: [AMPS] glitch resistors
From: (Tom Rauch)
Date: Sat, 8 Sep 2001 15:35:06 -0400
Hi Kim,

 Thats not correct - why you forget the selfinduction in the trafo ! 
> How do you think it behaves for lets say  even  1mS arc ?  Yes, the
> rise in voltage will NEVER travel through the trafo, why the "pulse"
> is at that short time  !!    You may transfer pulses at longer period
> yes, but not that short - they will "die" relatively short time after
> entering the trafo.

The high dump current ideally never makes it to the transformer. It 
comes from the capacitor. If you have put the glitch resistor 
between the transformer and the capacitor bank on the negative rail 
side, that is an even bigger problem!

Now you have a glitch resistor or fuse subjected to many high 
repetitious pulses of many amperes as the amplifier is running 
normally. This will cause an actual material change in the fuse, and 
also fatigue a resistor. Not only that, the ratio of glitch current to 
operating current is smaller yet, so the fusing device is less reliable 
in operation and much slower in operation when you depend on it!

Worse yet, the capacitor can still simply dump into the short, and 
that is what the real problem is all along!

There is no way to accomplish glitch protection unless the resistor 
is just after the energy storage (the filter capacitor). It is also very 
unsafe to put in in the negative or ground lead!!

It does not work in grids, it does not work in cathodes, it does not 
work on the transformer. 

It will somewhat work on the negative rail BUT that requires 
everything including the filter capacitor be well isolated from 
chassis! That is a very unsafe and unreliable thing to do, and also 
allows the glitch to have a very short but high peak current as the 
components on the negative rail charge to full supply voltage (but 
negative of course).

In any case, the resistor always has to handle the full supply 
voltage across the leads without internal arcs.

73, Tom W8JI 

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