[Heathkit] How about the SB-220?

[Carl]

----- Original Message ----- 
From: "Jim Shorney" <jshorney at inebraska.com>
To: <heathkit at mailman.qth.net>
Sent: Saturday, August 22, 2009 3:37 PM
Subject: Re: [Heathkit] How about the SB-220?


> On Sat, 22 Aug 2009 12:32:27 -0700, Paul Baldock wrote:
>
>>I'm not sure this is true. I have rebuilt two SB221's and grounded
>>the grids directly. This does give more gain and allows you to turn
>>the driver rig down. Turning the driver down from 100W to 90W on a
>>12V rig greatly improves its IMD and more than the negative feed back
>>that the amp "may" have with the Heathkit design.
>>
>>I have had no instability problems and the output is very clean. I'm
>>not aware of any modern 2 X 3-500Z amps that use the Heathkit method,
>>they all directly ground the grids.
>
>
> After reading all the pros and cons of this idea, I came to the conclusion 
> that
> the reasons for directly grounding the grids made more sense (to me) than 
> the
> alternatives. I grounded the grids in my L-7 and it has been running great 
> that
> way. FWIW.

Which goes against what the original designer recently said on another 
forum.The original way had a 2-3dB IMD improvement which is identical to 
what Ive measured as far back as the early 80's with the SB-220.

Carl
KM1H


>
> 73
>
> -Jim
>
>
> --
> Ham Radio NU0C
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