[AMPS] Another arc question

[Geurts, Gerard]

Jon Ogden wrote
> What do you call cutoff?  Zero mA plate current? 
> 
Yep, or maybe something like 50 micro-A in real life. Certainly not 50
mA. In a typical amateur radio GG amplifier a series resistor is used to
provide 'cut off bias'. This can of course only work if some current
flows through this resistor. 

> It certainly wasn't 
> keyed and was just idling.  Even in class AB operation some current is
> 
> likely going to be drawn as just quiescent current.  Idle current on
> the 
> 4-1000A is specified to be 80 mA.  Maybe I am just missing something 
> about cutoff.  
> 
80 mA is the idle current for class AB. This does not mean that anything
less is 'cutoff'. Cut off is when the tube (valve in this country) is
cut off, meaning there is no current flowing.

Oxford Advanced Dictionary of Current English says;

Cut off, (a) remove, (b) stop, interrupt, isolate

The (a) definition refers to limbs and fingers, the (b) definition talks
about electricity and gas supply. Note that the definition says 'stop',
'interrupt' and 'isolate', not 'reduce'.

What is Webster's definition?

> >I thought the whole idea of using Rich's suppressor is to stop
> >parasitics from happening in the first place. Now you are telling us
> >that what happened in your amp has to be caused by parasitics. While
> >using Rich's suppressors? Apparently they are not as good as some
> people
> >think. Or your amplifier is so badly constructed that even Rich's
> >suppressors won't help anymore. 
> 
> Well, you raise a good point.  These are the EXACT same thoughts that
> ran 
> through my head.  Mind you, I didn't construct my amp from the gound
> up.  
> It was purchased from an estate sale and I am doing my best to make it
> 
> work.  So unless I completley rebuild it (which may have been easier
> in 
> the long run), I am stuck with some limitations.
> 
> Perhaps Rich's suppressors aren't as good as some think.  Perhaps it's
> my 
> amp.  This is why I am calling everything I am doing experimenting.  I
> 
> think that even Rich will admit that his supressors don't necessarily 
> cure all ills.  They just make them less likely to happen.
> 
> I am going to continue to try working with both his supressors and 
> designs of my own.  If his don't work, they don't work and Rich will
> be 
> proven wrong.  However, I have heard of no one who has said that his 
> supressors made their amp unstable.  
> 
Agree. However, I would start with getting the basics right and cure the
last little problems with a suppressor, before spending a lot of time on
trying different suppressors. Maybe rebuilding from the ground up is the
best solution.

> So,I am assuming that there is 
> something else wrong with my amp.  What, I don't know.....Stay tuned.
> 
Cheers

Gerard

PA3DQW (my real call)
MoAIU (my present home call)
AA3ES (only got this one for a laugh, because they are so easy to get)


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