[AMPS] ARCING MORE

[Rich Measures]

>At 23:04 15/04/98 +0100, you wrote:
>>Rich Measures wrote:
>>> My guess is that when a new Tune C is installed, or 
>>>when new plates are installed, the intermittent arcing problem will not 
>>>go away.  
>>
>>That's probably true. Replacing the plates is probably necessary, but
>>it's only treating a symptom. It isn't treating the root cause.
>>
>
>It may be. Once the capacitor arced and the plates became deformed
>the arc persisted. The original cause of the arc was operator error,

perhaps it was one of the causes?  Sometimes things are not as simple as 
they seem.  

>much of that cause will be treated by the extraction of the cost of
>the repairs from the users bank balance and lost free time during
>a major opening etc. 
>
>The failure was not a failure in the tuning capacitor. Something 
>else may be dead, but if the amplifier works to 500W before arcing, 
>I can't think what it might be, except perhaps a shorted anode 
>blocking capacitor. That is easily tested.
>Mike

A shorted blocking cap puts hv dc on the tank coil, the other end of 
which goes to dc ground through a rf choke.  

Before attempting to repair the Tune C, I would measure the breakdown 
potential with a high-pot. tester.  .   and I would measure the R of the 
vhf suppressor resistors.  .  Alas, 'tis better that the Tune C arcs, 
than bandswitch contacts.  

cheers
Rich...

R. L. Measures, 805-386-3734, AG6K   


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