Chuck -
OK. Might try 'exercising' that trimmer a little and then trying to
re-zero against WWV.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-B, C-Line&
TR-4/C Service Supplement CDs
<www.k4oah.com>
Chuck Grandgent wrote:
First thing I tried was that C119 cap on the board.
Tweaked it just a little and the calibrator signal "popped in", nice
and strong.
Tried putting it back and it pretty much disappeared again.
So I guess depending on environmental parameters it was at a marginal
value for sustaining oscillation.
Thanks for all the pointers,
Chuck, K1OM
On Mon, Oct 25, 2010 at 5:42 PM, Chuck Grandgent <[email protected]
<mailto:[email protected]>> wrote:
Thanks Richard, thanks Garey, Lots of things to try and check,
will report back what I find after poking around.
Chuck
On Mon, Oct 25, 2010 at 5:15 PM, Richard Knoppow
<[email protected] <mailto:[email protected]>> wrote:
----- Original Message ----- From: "Chuck Grandgent"
<[email protected] <mailto:[email protected]>>
To: <[email protected] <mailto:[email protected]>>
Cc: "drakelist" <[email protected]
<mailto:[email protected]>>
Sent: Monday, October 25, 2010 1:52 PM
Subject: Re: [Drakelist] R4B erratic crystal calibrator
Yes, C192 was also part of the Hayseed recapping.
I will check D16.
The erratic operation (better characterized as failing to
stay in
oscillation) was there both before and after the
recapping, with the same
modus operandi.
I do also have a spare 100khz crystal, same form factor, I
suppose I could
try that too.
Chuck, K1OM
On Mon, Oct 25, 2010 at 4:37 PM, Garey Barrell
<[email protected] <mailto:[email protected]>> wrote:
Chuck -
Does Tom's kit include C192? I think it does. If not
....
Also D16.
And with the erratic operation, solder joints on C190,
etc. Tough places
to solder.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-B, C-Line&
TR-4/C Service Supplement CDs
<www.k4oah.com <http://www.k4oah.com>>
D-16, R-158, R-157 C192, C-190, all appear to be part of a
low voltage supply that feeds the calirator and nothing else.
Looking at the junction of C-190 and the emitter of Q-9 should
tell if its working. This is a half-wave rectifier fed by the
12V filament supply with large filter caps so the DC out of it
should be more than 6 or 7 volts, anyway, it should be there
all the time. The calibrator is switched by lifting a ground
at the source of TIS-34, the oscillator. Its possible the
function switch is intermittant, maybe not likely but its
worth cleaning the contacts on S-3 front. I don't remember if
the transistors in this circuit are in sockets or soldered in,
if in sockets wiggle them and if soldered it might be worth
re-flowing the solder. Also, Garey often recommends working
any screws that are used for grounding. This kind of
intermittant sounds like a heat problem but even intermittant
switches can be affected by heat.
The output of the calibrator is available at the antenna
input to the receiver and that is a convenient place to check
for its presense and for adjusting the calibration. Also, work
the calibrator adjusting capacitor. I think this is a very
unlikely cause but won't hurt anything.
--
Richard Knoppow
Los Angeles
WB6KBL
[email protected] <mailto:[email protected]>
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