On Jul 20, 2006, at 7:07 AM, Mike Schatzberg wrote:
> Hello Amp Fans:
>
> I have experimented with "grid fuse", while investigating grid
> equalization
> and trying to eliminate the need for using matched pairs of triodes.
>
> I believe what I tried at the time was about a 27 ohm 1/4 watt
> resistor.
>
> What I found was that the resistor was very sensitive to grid
> current peaks.
> The value that I selected for use with a pair of 3-500ZG triodes,
> in an SB
> 220 amplifier, seemed to be very sensitive to slight over drive, or
> so it
> seemed.
>
> The resistor would open circuit perhaps once in 3 months, while I
> tested
> this system on the air in daily use. I can only assume that high
> current
> peaks caused it to open, I never heard any arcing or other anomaly
> from the
> amp.
Mike S.: We use 30-ohm, 0.25W resistors as fuses and they will carry
normal SB-220 grid current without changing value. With serious
mistuning, they will darken but remain intact.
Were your failed resistors slow-roasted, or did they just blow open
suddenly?
>
> ...ilman/listinfo/amps
>
R L MEASURES, AG6K. 805-386-3734
r@somis.org
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