[Amps] Parts question.
R.Measures
r at somis.org
Fri Jul 30 10:22:07 EDT 2004
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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>
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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