[Drake] T4XC on AM

[Al Parker]

hi Jon,
    I've been away most of the day, just saw your msg & Barry O's response.
Barry's right, "you gotta watch it" so you don't cause problems.  Drake knew
what they were doing, in probably 99% of what they did, & we can screw it up
if we're not careful.
    But, caveat emptor, there has been a slighly published mod to help AM.
I haven't tried it, but I suspect the last "poster" did, Haney, K2XN.  I
think he's on this list, maybe he's already responded directly, but here it
is:
=====================
Date: Fri, 20 Nov 1998
From: Haney Howell <howellh@winthrop.edu>
Subject: Found!  T4X AM mod
    Like Buddha, heavy contemplation led me to the R4B/T4XB manuals during
lunch.
Here's the mod:
    On the schematic, look for V11, the 6AU6A in the AM section.  Parallel a
25-30K 1 watt resistor with R57, the 15K 1 watt.  Make certain you have the
right 15K resistor... there's also a 2 watt in the circuit.
    You'll find this resistor on the vertical board.  There's plenty of room
and
it's easily reversible.
    Because of the increased carrier, I take extra care in tuning and
setting the
audio gain.  No need to beat the precious finals to death!
    This should be the same circuit for all of the T4X line.  This
information is
from the T4XB manual.
Haney  K2XN
=================

    Looking at the skem, this resistor is physically between the screen &
plate of the AM mod. tube.  If I follow the skem right, it increases screen
voltage on the tube when in AM mode, thus increasing modulator output, which
is applied to the screens of the Driver & finals.
    Like Barry says, check what you're doing carefully with a good audio gen
& scope, if you are concerned about quality, and stress to the finals, in
the T-4Xx and your linear.
73,
Al, W8UT
New Bern, NC
BoatAnchors appreciated here
http://www.thecompendium.net/radio/
http://www.hammarlund.info

----- Original Message -----
From: <K6jek@aol.com>
To: <drake@mailman.qth.net>
Sent: Sunday, November 17, 2002 1:02 AM
Subject: [Drake] T4XC on AM
> Anyone have any experience tweaking a T4XC on AM?  I would like a little
more
> resting carrier and actually a little less peak since I'm driving a
linear.
>  Seems like unbalancing the modulator a little more and just plain turning
> down the gain might do it.