Tom, that makes sense and sounds like a must do modification. I can't
contribute anything to this discussion so will humbly bow out.
73,
Gerald K5GW
In a message dated 2/12/2010 9:49:21 A.M. Central Standard Time,
tomp@prohigh.com writes:
>From Rick Measures:
Converting a SB-220 or TL-922 from V-cutoff bias to R-cutoff bias: will
prevent this from happening. The conversion: •• 1. Remove +110v from NC
bias
contact on relay without disconnecting the +110v lead to the coil. 2.
Unsolder the lead of the 100k R that connects to the NC bias contact, move
it to the NO bias contact and solder it . When finished, the 100k-ohm R
should connect between the arm and the NO contact. During Rx, the drop
across the 100k R is c. 25v. During Tx, the 100k is shorted out by the
relay.
This prevents a transformer meltdown in event of a cathode to grid short
On Fri, Feb 12, 2010 at 10:46 AM, <TexasRF@aol.com> wrote:
> Tom, I am not familiar with the terms "v bias" and "r bias". Are saying
> the zener bias diodes have been replaced with resistors?
>
> 73,
> K5GW
>
>
> In a message dated 2/12/2010 9:40:18 A.M. Central Standard Time,
> tomp@prohigh.com writes:
>
> Only mod was V bias to R bias. At key down, there is 7.5V at the zener.
> Maybe I should do the diode bias or get a 5.1V zener, or maybe just the
old
> tubes are a little soft
>
> On Fri, Feb 12, 2010 at 10:38 AM, Carl <km1h@jeremy.mv.com> wrote:
>
> > Did you modify the bias circuit or check the voltage?
> >
> > Carl
> >
> >
> >
> > ----- Original Message -----
> > *From:* Tom Prohigh <tomp@prohigh.com>
> > *To:* Carl <km1h@jeremy.mv.com>
> > *Cc:* amps@contesting.com
> > *Sent:* Friday, February 12, 2010 10:34 AM
> > *Subject:* Re: [Amps] TL-922 voltage / bias
> >
> > There are 2 tubes in the TL-922. The grids are DIRECTLY connected to
> > ground, I removed the caps and chokes and also put in a second ground
> wire
> > from VC1. This eliminated some arcing/parasitics I was having. The
> tubes
> > are original Eimac 3-500Z not 3-500ZG. The color on the plates is
fine,
> no
> > color at idle and red/orange at full drive. I do get about 600-700W
out
> on
> > CW, but only about 1000 key down on SSB on 20M. 80M is somewhat higher
> >
> > Tom - AB3FL
> >
> > On Fri, Feb 12, 2010 at 10:30 AM, Carl <km1h@jeremy.mv.com> wrote:
> >
> >> That idle current is fine for 1 tube and the voltage drop is
excessive.
> >> Start by measuring the grid chokes for an open or looking for color on
> both
> >> plates.
> >>
> >> Carl
> >> KM1H
> >>
> >>
> >> ----- Original Message ----- From: "Tom Prohigh" <tomp@prohigh.com>
> >> To: <amps@contesting.com>
> >> Sent: Friday, February 12, 2010 9:47 AM
> >>
> >> Subject: [Amps] TL-922 voltage / bias
> >>
> >>
> >> I have recently aquired a TL-922. It is on a stiff 240V line which
> >>> actually
> >>> measures 245V. No load voltage on CW is 2200 and on SSB is 3100.
> Under
> >>> full load the CW drops to 1900V @ 600ma and the SSB drops to 2400V @
> >>> 800ma.
> >>> Is there really suppose to be this much drop? It has the original
> 200uf
> >>> caps in it and I was thinking about replacing them with 560uf units.
> >>> Also
> >>> the grid bias on CW is 60ma and on SSB 120ma which seems a little
low.
> >>>
> >>>
> >>> thanks
> >>>
> >>> Tom - AB3FL
> >>> _______________________________________________
> >>> Amps mailing list
> >>> Amps@contesting.com
> >>> http://lists.contesting.com/mailman/listinfo/amps
> >>>
> >>
> >>
> >
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|