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Re: [Amps] Parts question.

To: Will Matney <>
Subject: Re: [Amps] Parts question.
From: R.Measures <>
Date: Fri, 30 Jul 2004 07:22:07 -0700
List-post: <>

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

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:
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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Richard L. Measures, AG6K, 805.386.3734.

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