Why change something that works Lou; is that your recommendations?
Since the LK-500 has an ideal layout for input-output isolation it is
stable.
I cant say the same about some other amps with the grids directly grounded.
Carl
KM1H
----- Original Message -----
From: Louis Parascondola
To: km1h@jeremy.mv.com ; w7ry@centurytel.net ; rkmassoc@comcast.net ;
amps@contesting.com
Sent: Monday, June 03, 2013 1:10 AM
Subject: Re: [Amps] Source of Mica Caps?
Carl, your beloved LK-500 has hard grounded grids. Did you change that
design and float them? If not what might be the difference in that design
that makes it OK? Always wondered about that.
Ive yet to
have instability in a well built and updated SB-220, even on 6M, with the
Heath design.
-----Original Message-----
From: Carl <km1h@jeremy.mv.com>
To: Jim W7RY <w7ry@centurytel.net>; Randall K Martin <rkmassoc@comcast.net>;
amps <amps@contesting.com>
Sent: Sun, Jun 2, 2013 8:03 pm
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 seperate 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
----- Original Message -----
From: "Jim W7RY" <w7ry@centurytel.net>
To: "Randall K Martin" <rkmassoc@comcast.net>; <amps@contesting.com>
Sent: Sunday, June 02, 2013 4:38 PM
Subject: Re: [Amps] Source of Mica Caps?
Ground the grids directly and remove the caps and chokes. BUT install a
glitch resistor in series with the B+ and a diode from chassis ground to
B- (anode to ground, cathode to B-). W8Ji's web site has lots of
information on this.
73
Jim W7RY
-----Original Message-----
From: Randall K Martin
Sent: Saturday, June 01, 2013 5:39 PM
To: amps@contesting.com
Subject: [Amps] Source of Mica Caps?
Does anybody know where I can buy a replacement for one of the mica grid
bypass capacitors used in the Heathkit SB220? I believe they are 115 pf.
Can't find anything close in the mouser catalog.
73
Randy K0EU
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