Date: Sun, 2 Jun 2013 19:58:58 -0400
From: "Carl" <km1h@jeremy.mv.com>
To: "Jim W7RY" <w7ry@centurytel.net>, "Randall K Martin"
<rkmassoc@comcast.net>, <amps@contesting.com>
Subject: Re: [Amps] Source of Mica Caps?
I still dont understand the claim made by a few that increasing gain and
power output increases stability when hard grounding the grids.
I would take various web sites with a grain of salt and try to separate the
good from bad.
The 115pf caps were chosen by Heath at the end of the SB-220 run and a
bulletin suggested changing them. The SB-221 and HL-2200 use the 115pf but
Ive replaced with whatever 110 and 120pf I come across in bulk. Ive yet to
have instability in a well built and updated SB-220, even on 6M, with the
Heath design.
Carl
KM1H
## TL-922 are rock solid when oem suppressors used and grids directly
grounded, and chokes tossed.
Ditto with drake L4B..and just about every other amp that floats the grids with
caps... including SB-220.
## Sb-220 with grids directly grounded to chassis works superb on 6m. I
have seen KM1H SB-220
6m conversions, where the grids were grounded to chassis...after the fact by
the owner..works great.
## The 25 ohm DC resistance of the chokes used in the SB-220 isnt doing you
nay good..just more
unwanted V drop. The DC resistance of the chokes used in the Drake L4B
is less than 1 ohm.
I still tossed the chokes and caps in all 4 of my L4B amps.
Jim VE7RF
.
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