[Johnson] Ranger Chirp

[Glen Zook]

Replace the 6AU6 type with a 6AH6 type.  Direct
replacement except that you might have to "touch up"
the calibration variable capacitors since the 6AH6 has
a slightly different interelectrode capacitance than
the 6AU6.  The inductors should not have to be
"touched".  Heath did this to help stabilize the VFO
in the Apache.  The earliest versions used the 6AU6
while later versions used the 6AH6.

Replace the 0A2 with an 0B2.  This drops the regulated
screen voltage from 150 volts to 108 volts.  Usually
nothing has to be changed in the transmitter.

If this doesn't completely "cure" the problem then use
the 0A2 that you removed from the screen circuit to
regulate the plate voltage of the VFO tube.  This will
require a slight modification including the addition
of a 7 pin minature socket.

Glen, K9STH


--- "Harry Vaught, KT4AE" <kt4ae at bellsouth.net> wrote:

I decided to try to get rid of the CW chirp in my
Ranger VFO.  It doesn't chirp using a crystal.

I searched the archives and found a number of
suggestions some of which I implemented:
 
- adjusted the keyer.  Incidentally, I've always
thought the adjustment didn't work, but it turns out
that it was wired backwards so turning it all the way
CCW didn't key the VFO.  I'd never tried all the way
CW before.  Duh.  Hey, it worked on AM.

- in the VFO, I replaced the 6AU6 with a 6AU6WA and
replaced the 0A2 (twice).  You should hear the chirp
with the top of the VFO off.  I cleaned the
bandswitch, which cured a long-standing problem with
low drive on 80M.  Checked R3.  It was 19.4K which is 
within 10%.  I had replaced it with a pair of 38K
4watt units when I got the Ranger.









Glen, K9STH

Website:  http://k9sth.com


       
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