R L Measures wrote:
>
> On Aug 30, 2006, at 1:17 PM, Steve Thompson wrote:
>
>>
>>>>> Any change in current causes a resonant circuit to ring. Ringing
>>>>> amplitude depends on how fast the current changes and on Q. Faster
>>>>> and
>>>>> more Q =s more V. I have heard from more than a few TL-922
>>>>> owners who
>>>>> report that a big-bang, flashover, and damage occurred when
>>>>> their 922
>>>>> was un-keyed.
>>>>
>>>>
>>>> Sure, but how fast does the current change? By the time the decoupling
>>>> capacitors have charged to allow the tube to drift into cutoff, I
>>>> doubt
>>>> the rise time alone is going to make the anode ciruit ring at vhf.
>>>
>>>
>>>
>>> During the Grate Parasitics Debate in 1996, a member of the audience
>>> hauled his SB-220 to work and loosely coupled the anodes to a HP
>>> spectrum analyzer. When the 220 was keyed, he observed damped-wave
>>> ringing at 112MHz at on And at off.
>>
>> I wish I could reproduce that. I've tried repeatedly with spectrum
>> analyser and 'scopes and only ever find operating frequency ringing,
>> even with suppressors removed.
>
>
> Apply no driving signal and rapidly key the T/R bias.
Did that, no result. Hence my post.
Steve
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