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[AMPS] Blown TL922A... What to do?

To: <amps@contesting.com>
Subject: [AMPS] Blown TL922A... What to do?
From: 2@vc.net (measures)
Date: Mon, 11 Sep 2000 11:37:07 -0700
>
>measures wrote:
>>
>>>
>>>measures wrote:
>>>>The grid protection circuits I am talking about are those that provide no 
>>>>protection because the transistor that interrupts has too low a current 
>>>>rating and it shorts during a glitch -- thereby affording no protection.  
>>>>
>>>Failure of that transistor to survive a glitch/arc/parastic/flash-
>>>over/whatever is a simple DC design fault that can be cured by a 10K
>>>resistor. 
>>>
>>A 10k-ohm resistor can prevent C-E shorts due to excessive collector 
>>current?
>>
>>>I don't think that's a good reason to remove grid current protection for
>>>normal operation.
>>
>>Replacing a shorted transistor with a fuse-R is hardly removing 
>>protection.  Shorted transistors afford no protection because they can 
>>not turn off.  
>
>We may be talking about different transistors. Let's start again.
>
>Where in the circuit is the transistor that you say burns out in a
>glitch?

In series with the grid current meter shunt.  This transistor must open 
to stop the flow of excessive grid current.  If the transistor has too 
much current, it C-E shorts.  
>
>Why do you believe that it should be removed, if that also involves
>disabling grid current protection in normal operation?

Grid current protection is disabled by the C-E shorted transistor.  By 
replacing the shorted transistor with a fuse or fuse resistor, protection 
is restored.  
>
end

-  Rich..., 805.386.3734, www.vcnet.com/measures.  
end


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