Re: [Amps] Parts question.

[R.Measures <r@somis.org>]

On Jul 29, 2004, at 9:17 PM, Will Matney wrote:

> Well,
> Does anyone know if they still make ceramic disc capacitors with built 
> in spark gaps? They used to use these a lot in tube type color tv 
> sets. These were made to arc if the capacitor voltage was somewhat 
> exceeded. On the top of the disc, there was molded in a small spark 
> gap. It had a little cut in the ceramic separating the two electrodes. 
> I was thinking these would be handy in tetrode and triode circuits if 
> they're still being made. I've not seen any in years anywhere but 
> haven't looked either that much until now. If they do still make them, 
> who is and where is a possible supplier? Thanks all in advance.
Will --- I build and test my own spark gaps for use in grounded-screen 
tetrode amplifiers to protect the cathode circuitry (i. e., the bias, 
and screen supplies, plus the fil xfmr, from anode-chassis flashovers.  
Another protection method is sacrificial 3A - 10A diodes.  When the piv 
of the diodes is exceeded, they short.  See Ds at:
http://www.somis.org/D_a_05.GIF
A spark gap would go at the same place as Ds.
--  Another potential problem is amplifier tank arcing following a 
C-flashover in an antenna tuner.  The fix is to connect a spark gap in 
series with a 50 - 100 ohm resistor, and connect it between the Tune-C 
and the Load C.  The gap needs to be set for c. 20% higher than than 
the anode PS V.  
end

> Will Matney
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> Amps@contesting.com
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Richard L. Measures, AG6K, 805.386.3734.  www.somis.org

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