[Boatanchors] 30S1 bis query

[Jack Taylor]

Hi Glen John and Gary,

I was wondering about the references to the KWM2A/32S exciters, but the 30S1
manual refers to the amplifier bias voltage as being
adjusted for a 200 ma reading presumably on the amplifier Ip meter.  To me
the manual is a little vague in this area and should read
"With PTT applied set bias control to read 200 ma Ip in SSB mode with no
drive", if that's what's intended.

Appreciate the suggestions and my next step will be to measure the screen
voltage, once I figure out how to safely do so.  Again,
the manual is vague on what the screen voltage should be.  The block diagram
indicates 200V, but then the block diagram shows
the bias supply as being 50V, where I'm measuring -66V or less, depending
upon where the bias control pot is set.

Incidentally, I did allow the filaments on the 4CX1000A to cook for a couple
of days before applying power.  A few gremlins
surfaced.  First the plate meter would indicate 600 ma when keyed with no
drive.  Also at separate times, a contact on the step
relay froze as did a contact on the transceive relay.  Getting to the
transceive relay was easy but restoring it was not.  Then an
intermittent showed up on the PTT line at the RCA plug, which caused some
confusion.  The 600 ma keyup problem was
tracked to a dirty wiper on the bias control pot.  Discovered this with the
unit powered down and an ohm meter across the
output of the bias supply.  Over time, the resistance would sharply vary.
Cleaned the control which also took care of a 20
volt sawtooth on the bias supply.

Still unable to adjust the bias control for a 200 ma resting current reading
in SSB mode.  Replaced the final tube but really not
much change in symptoms.  In CW mode, the amplifier appears to be OK.  Just
screwy in SSB.  That's why I asked the
question about the bias setting.  Presumably as one goes towards zero bias
in AB1, the plate current should increase.
According to the 4CX1000A data sheet for AB1 operation, the bias should
be -55 volts.

Perhaps a measurement of the screen voltage will solve the mystery.

73 de Jack - N7OO



----- Original Message ----- 
From: <eldim at att.net>
To: "Jack Taylor" <jack at n7oo.com>; <boatanchors at mailman.qth.net>
Sent: Monday, August 14, 2006 5:45 PM
Subject: Re: [Boatanchors] 30S1 bis query


> Hello Jack,
> This refers to the Exciter Plate Current of 200 MA.  i.e.  When running a
KWM-2/2A Transceiver, or 32S Line Transmitter you normally donot run the
plate over the recomended max plate current of  220MA when Operating
"barefoot" or without an RF Amplifier.  When connected to a Linear
Amplifier, it is recommended to reduce the drive to 200ma with the Loading
Control/Plate Control, with the final dip being the Plate Contol.  In
running 200 mA RF Drive to the 30L1 or 30S-1 you insure longer life to the
Amplifier Input Tuned Circuit.  I have seen Input coils that were toasted
from overdriving them.
> 73,
> Glen Galati, KA7BOJ
> Tacoma, WA
>
> -------------- Original message from "Jack Taylor"
<jack at n7oo.com>: -------------- 
>
>
> > I'm having a problem understanding what the 30S1 bias voltage should
> > approximately
> > read in the SSB and CW positions. The manual says the "voltage necessary
to
> > set
> > idling plate current to 200 ma". On mine, the bias can be adjusted from
> > approximately
> > -38 to -65 volts and I never see anymore than zero plate current with no
> > drive.
> >
> > 73 de Jack - N7OO
> >
> >