[Amps] Grid Current Advice

[Michael Tope]

If you assume an input impedance of 58 ohms (115 ohms/tube
divided by 2 for the pair) and 100 watts of drive power, that works
out to around 76 volts RMS grid-to-cathode potential. With a 40W
maximum grid dissipation (2 x 20 watts/tube) this works out to a
maximum grid current for a pair of 3-500ZGs of 525mA. That
seems a bit high to me, but it is consistent with the guidelines for
the Ameritron AL80B, for instance, which specifies a maximum
grid current for a single 3-500Z as 250mA.

http://www.ameritron.com/man/pdf/AL-80B.pdf

Personally, I don't think I would run a pair of 3-500ZGs much
beyond 300 to 350 mA of grid current, just to be safe.

Mike, W4EF.........................

----- Original Message ----- 
From: <amps-bounces at contesting.com>
To: <keith at dutson.net>
Cc: "Amps" <amps at contesting.com>
Sent: Monday, August 15, 2005 7:52 PM
Subject: Re: [Amps] Grid Current Advice


There is no max grid-I rating.  The max rated grid dissipation is 20w,
but several experimenters have found this to be somewhat conservative
-- probably because the grid is made from Mo, which melts at 2617ºC.

Figuring grid P --- According to "Care and Feeding ... ... ..." ,
grid-dissipation is approx. the indicated DC grid current multiplied by
the RMS grid to cathode potential.



cheers, Keith
.
On Aug 15, 2005, at 7:22 PM, Keith Dutson wrote:

> What is the maximum recommended grid current for a pair of Eimac 3-500G
> tubes?  Thanks.
>
> 73, Keith NM5G
>
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>

Richard L. Measures, AG6K, 805.386.3734.  www.somis.org

_______________________________________________
Amps mailing list
Amps at contesting.com
http://lists.contesting.com/mailman/listinfo/amps