[Amps] SB-220 saga continues

[Pete Smith]

My Mark 5 has one.  My SB-220, though, now has a 300-volt FET to switch the 
vacuum relays.

73, Pete

At 11:45 AM 11/9/2008, Carl wrote:
>Most xcvrs havent used a relay in decades. SS doesnt like 120V @ 100 ma
>
>Carl
>KM1H
>
>
>----- Original Message -----
>From: "Joe Subich, W4TV" <w4tv at subich.com>
>To: <amps at contesting.com>
>Sent: Sunday, November 09, 2008 10:20 AM
>Subject: Re: [Amps] SB-220 saga continues
>
>
> >
> > The keying line (PTT relay) in the SB-220 is +120 V DC.  The contacts
> > of the "Linear" or "Send" relays in most transceivers can not handle
> > the voltage and current "spike" generated by the high voltage PTT
> > circuits in the older amplifiers (SB-200, SB-220, L4, L7, TL-922,
> > etc.).
> > You will probably need to replace the "Linear" or "Send" relay in your
> > transceiver (if you are lucky, that will be all).
> >
> > I suggest adding a keying buffer (e.g. Ameritron ARB-704), modifying
> > the SB-200 with the internal Harbach Electronics soft key circuit
> > (www.harbachelectronics.com/main/page_products_sb220__sb221.html),
> > or converting the SB-200 to faster, low voltage relays and electronic
> > bias switching.
> >
> > 73,
> >
> >   ... Joe, W4TV
> >
> >
> >
> >> -----Original Message-----
> >> From: amps-bounces at contesting.com
> >> [mailto:amps-bounces at contesting.com] On Behalf Of Roger (K8RI)
> >> Sent: Sunday, November 09, 2008 12:34 AM
> >> To: ke1fo at arrl.net
> >> Cc: amps at contesting.com
> >> Subject: Re: [Amps] SB-220 saga continues
> >>
> >>
> >> 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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> >> >
> >> >
> >>
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