SB220 BIAS/ RELAY PROBLEM

[JBA]

Glenn,
Have you disconnected the Ameritron Interface (whatever that is), and tried
to key the amp manually? This would help isolate the trouble. You say that
the relay releases when you unplug the relay connector, maybe the trouble is
in the Ameritron Interface unit instead of the amp.
Good luck!
de Benton wb5twc


----- Original Message -----
From: "ghaffly" <ghaffly at STIC.NET>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Saturday, April 27, 2002 12:51 PM
Subject: SB220 BIAS/ RELAY PROBLEM


> Hello all , currently have a problem with an Sb220. Details :
>
> Current setup : Icom 706 MK2 with an Ameritron interface to an SB220.
>
> At cold start linear turn on is Ok and tubes are biased off , no plate
> current .Key the linear in Cw mode and interesting things happen.
> #1 After releasing the Cw key ,linear's relay should open and plate
current
> should
> be zero. This Sb220 relays stays closed with 100 mils plate current.
> #2 The only way to drop the relay is to pull the relay connector from the
> rear socket
> and then the relay drops out and no plate current. Plug the relay
connector
> back in
> and with zero Rf applied relay closes drawing plate current. There seems
to
> be a faint
> but audible squeal prior to relay closure.
> #3 If you turn the linear off for a minute or so after #2 , it is ok until
> you apply Rf again.
>
>
> The voltage on the relay coil looks Ok , about 126v. Plate voltage Ok.
> Since the problem is going From Tx to Rx whats keeping the relay closed?
> Maybe a bad ZD1( 5.1 v).  Also any ideas on the faint squeal heard before
> relay closes?
>
> Any ideas would be appreciated.
>
> Glenn
>
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