[Johnson] Ranger Chirp

[jeremy-ca]

VR tubes are notorious for poor regulation as strange as it may seem.
I sometimes have to go thru 3-5 to get one that will hold a constant 
voltage, even under a constant load. This includes new ones as well as pulls 
from unknown sources. The 7 pin miniature are worse than the octals.

Some require adjusting the value of the limiting resistor to keep them 
within their min-max operating currents.

In many cases it would be easier and with better results to use a few zeners 
(as few as possible).

Carl
KM1H




----- Original Message ----- 
From: "Glen Zook" <gzook at yahoo.com>
To: <kt4ae at bellsouth.net>; <johnson at mailman.qth.net>
Sent: Saturday, September 22, 2007 4:27 PM
Subject: Re: [Johnson] Ranger Chirp


> 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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