I have a friend who is prepping an SB220 for use with his K3. He has built but not installed as yet a ""Softstart" and a "Softkey" circuit. He also replace a sluggish fan and some caps. The "Softkey" is needed as I think the SB220 uses high negative voltage on the key line and the K3(S) won't tolerate a negative keying voltage.
Connections would be a PTT cable and RF from radio to amp. Set the drive power with the K3 power control, and you won't need ALC.
Enjoy your amp and good luck!
Sent from my iPad
...bc nr4c
> On Apr 3, 2017, at 1:36 AM, Robert B. Weinstock <
[hidden email]> wrote:
>
> Good morning. Does anyone have any experience using a K3S to drive a Heath
> SB-220 linear amplifier? This is a 40-odd year-old amplifier with two Eimac
> 3-500Z tubes. My questions are: (1) What connections need to be made
> between the K3S and the SB-220; how much drive is likely needed; and what
> would be needed to run full break-in on CW? The SB-220 does not have its
> own break-in circuitry, but there are numerous vacuum relay-based
> modifications out there.
>
> (And yes, I do have a KPA500 that I expect to use most of the time. I just
> want to be able to switch over to the SB-220, which provides far more power
> output.)
>
> Thanks.
>
> 73, Bob, W3RQ
> Takoma Park, Maryland
> K3, P3, KPA500, KAT500
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