Well, it has been a long, strange trip here.
Just finished a little experiment with the PTO and my K3. First of all, the
K3 is deaf as a post at 4.9 MHz ;-) but I did get enough of a signal through
a scope probe hooked to the PTO output to confirm that it's the PTO that is
shifting frequency.
Having confirmed that, my next step will be replacing the 3000 pF and the
zener - even though I'm fairly convinced the zener is okay (alright - I'll
replace the 3000 pF first...).
I have a sneaking suspicion that this may be one of the S.A.T. caps. If so,
it's going to be interesting since I no longer have a capacitance meter.
Steve Wedge, W1ES/4
"I can't complain, but sometimes I still do."
- Joe Walsh
If the above message appears, it came from Steve's Son of Laptop!
----- Original Message -----
From: "Garey Barrell" <k4...@mindspring.com>
To: "Steve Wedge" <w1es1...@earthlink.net>
Cc: <drakelist@zerobeat.net>
Sent: Friday, July 29, 2011 3:21 PM
Subject: Re: [Drakelist] R-4A PTO: It wasn't the transistors
Steve -
Yes, the PreMixer signal (V8) (BAND minus PTO) is the one that is piped
back and forth between the two units.
All you have to do is listen to the PTO signal itself on a separate
receiver. "0" on the dial = 5.455 MHz, "500" = 4.955. The BFO crystal is
5.595 MHz. The BFO is a tube, V3, which I believe we swapped way back
towards the beginning of this odyssey!! I also thought you had put a
counter on the PTO, but I guess that's another 'project'. :-) I
typically have three or four of these eMail projects going at one time,
which is why I like to keep the entire thread together. Makes it easier
to go back occasionally just to review just what path got us 'here'! :-)
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Steve Wedge wrote:
You know, Garey, I've been thinking about the xtal oscillator. It would
have to be part that doesn't get bandswitched - which would include THAT
transistor.
When the T-4X controls the frequency, it sounds great and never jumps
frequency. In looking at the schematic, I have been aware that the two
solid-state oscillators (PTO and LO for the band) get mixed in V8 (IIRC)
and that this combination gets overridden by the output of the T-4X's
premixer.
Looks like I am going to need a counter to find out. I am loathe to dig
into the T-4X because it's working so well and the PTO is much more
difficult to remove from it due to the volume of wires in the area.
73,
Steve, W1ES
Date: Fri, 29 Jul 2011 13:31:12 -0400
From: Garey Barrell<k4...@mindspring.com>
To: Richard Knoppow<1oldle...@ix.netcom.com>
Cc: drakelist@zerobeat.net
Subject: Re: [Drakelist] R-4A PTO: It wasn't the transistors
(entirely)
Message-ID:<4e32ee60.4060...@mindspring.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Richard -
Yes, one wonders...... :-) This type of 'dithering' is known in
PTOs, but although much less
common, a poor crystal oscillator such as the BAND or 2nd MIXER
oscillators 'could' present the same
way.
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