[Amps] SB-220 saga continues

[Roger (K8RI)]

Please do not cross post between reflectors.

Roger (K8RI)

Alfred Frugoli wrote:
> Hello everyone,
>
> So it seems I've got a problem with my SB-220.
>
> When the amp is off, but connected in the RF path, everything is fine.
>
> When I switch the amp on I've suddenly got lots of attenuation happening on
> the receive path.  Transmit seems fine - amp tunes OK etc.
>
> My first suspicion was that there were dirty relay contacts on the receive
> side.  Cleaned the contacts with no success.  Then I realized that the
> problem only occurs when the amp is on.  So a trip to the schematic tells me
> I don't understand.  In the RX mode the RF path through the amplifier should
> be the same as when the power is on.  So I'm not sure where my attenuation
> is coming from.
>
> Just testing it a few minutes ago I can make an S5-7 station almost
> completely disappear by turning on the amp, so I've got somewhere in the
> area of 20db of attenuation happening!
>
> Thoughts?
>
> Thanks.
>
> 73 de Al, KE1FO
>
> -----
> Visit my amateur radio contesting blog at ke1fo.wordpress.com.
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