Had this same attenuation problem occur in a 30-S1 I had a few years back.
Cleaned the rx/tx contacts with Caig chemical's Deoxit contact cleaner,
problem disappeared completely never to return.
73's,
Gary...wa6fgi
----- Original Message -----
From: "W7RY" <w7ry@arrl.net>
To: <ke1fo@arrl.net>; <amps@contesting.com>; "YCCC" <yccc@yccc.org>
Sent: Saturday, November 08, 2008 8:42 PM
Subject: Re: [Amps] SB-220 saga continues
> Sounds like the relay in the amp is energizing when you turn on the amp.
> My guess is that your relay contacts in your transceiver are stuck
> (shorted).
>
> Unplug the PTT cable from the amp or the rig. I but it works fine then. If
> so, you need to repair your rig. AND add a PTT buffer between the amp and
> the rig so it does not happen again.
>
> The PTT line of the SB220 has a .01 or .02 uF cap across the plug. When
> the transceiver keys the amp, the relay in the rig must short out the .02
> uF cap and this causes a pretty big arc across the relay contacts of the
> rig.
>
> 73
>
> Jim W7RY
>
> ----- Original Message -----
> From: Alfred Frugoli
> To: amps@contesting.com ; YCCC
> Sent: Saturday, November 08, 2008 8:23 PM
> Subject: [Amps] SB-220 saga continues
>
>
> 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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