On May 19, 2004, at 5:13 PM, Paul Erickson wrote:
I am fixing an FL2000b amp for a friend, and among other things the
grid choke is black from over heating. I am having trouble finding one
locally. It is one of the old receiving type millen/miller single
layer chokes. Anyone know where I can find a good replacement?
Paul -- Replacing the choke is not the fix. The choke was toasted
because of a burst of grid-I. The fix is to improve the VHF stability
of the amplifier so as to lessen the chance of burst in grid-I. Since
a Cu-wire choke is a poor fuse, and a burst in grid-I can damage a
572B, it would be better to limit grid-I with a fusing resistor of 30 -
39-ohms @ 0.25w. -- notes -- The resistor type: Carbon-film is
better then MOF for this application. // To protect the grid fusing
resistor from 10m RF from the adjacent anode, the grid should be
bypassed with c. 1500pF.
Ω≈
--
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cheers, Paul - VA7NT - email: va7nt@telus.net
"Those who hear not the music, think the dancers mad."
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Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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