[Heathkit] sb200/220 fan

Fri, 29 Nov 2002 20:35:45 -0500

Ive used original Eimac graphites as well a  Amperex and Chinese in those
amps.
Ive experienced some gas arcs with Chinese that can take out the zener and
other parts.
I now automatically use a string of  5 1N5408's reverse connected in place
of the zener. Bullet proof as I bake the tubes in plus they can take all
sorts of operational abuse.

the 1N4007's used in the Harbach conversion are too wimpy IMO also.

There are all kinds of mods I recommend for the 220 series, I wrote them up
some years ago and they made the rounds of several reflectors. Unfortunately
i didnt save a copy; something to do on a cold winter night.

One easy mod is to replace the VHF choke, RFC2, with a 10-12 Ohm 20W
wirewound resistor; NOT cement.
This will limit arc current to a safe value. That choke is series resonant
VERY close to the natural parasitic frequency of the tube and contributes to
problems.
It is perfectly natural for those tubes to outgas and arc occassionally; if
its controlled it wont cause damage.

Carl

----- Original Message -----
From: "Kurt W. Zimmerman" <[email protected]>
To: "'Carl Huether'" <[email protected]>; "Jim Shorney"
<[email protected]>; <[email protected]>
Sent: Friday, November 29, 2002 5:23 PM
Subject: RE: [Heathkit] sb200/220 fan

> Talking about the 3-500's Graphites, besides additional cooling, are there
> any other required mods needed for the graphite tubes in the SB220?
>
> 73;
> Kurt - W2MW
>
> -----Original Message-----
> From: Carl Huether [SMTP:[email protected]]
> Sent: Friday, November 29, 2002 5:21 PM
> To: Jim Shorney; [email protected]
> Subject: Re: [Heathkit] sb200/220 fan
>
> Its also real simple to tear down the fan, clean and relube.
> Amazing how well a freshened up one performs.
>
> On the same tack, the stock fan is marginal for graphite plate 3-500's.
> Alan
> Harbach offered a higher speed version that was nice, particularly for
> contesting. I dont know if the new owner has continued with it.
>
> Carl
>
> ----- Original Message -----
> From: "Jim Shorney" <[email protected]>
> To: <[email protected]>
> Sent: Friday, November 29, 2002 3:07 PM
> Subject: Re: [Heathkit] sb200/220 fan
>
>
> > -----BEGIN PGP SIGNED MESSAGE-----
> >
> > On Fri, 29 Nov 2002 14:53:23 -0500, Carl Huether wrote:
> >
> > >"Enough to do the job"
> > >Its never been actually specified. The 220 fan moves a serious amount
of
> > >air.
> >
> >
> > Not an answer to the question, but Rich Measures has some nice things
> > to say about the SB220 cooling system on his web site:
> >
> > http://www.vcnet.com/measures/sb220ci.html
> >
> >
> >
> > - --
> > Jim Shorney      -->.<--Put complaints in this box
> > [email protected]
> > [email protected]
> > Ham Radio NU0C
> > Lincoln, NE, USA
> > EN10PT
> > http://incolor.inetnebr.com/jshorney/
> > -----BEGIN PGP SIGNATURE-----
> > Version: 2.6.2
> >
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> >
> >
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