Ron -
OK, so much for my 'expertise'! :-) Looks like this may be one of the 5%.
Someone emailed me direct saying that they had sent the old crystal in to ICM and they were able to
provide a correct replacement. I'm not sure how that works, perhaps they 'knew' what it should be,
-OR- perhaps if they knew what frequency the BAD crystal was on, they were able to check for the
correct load at that frequency?!
You might consider sending your old one in along with the frequency you're getting with L1005 at mid
range.
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>
Ron Ries wrote:
Thanks for the response, Garey. I did specify 32 pf and have received/installed
that crystal only to find that it was, according to Royden Freeland at ICM, too
stiff. I replaced the ferrite slug with a brass slug and was able to pull it in
and calibrate the radio but it is operating at the extreme end of the operating
range of the adjustment pots. An engineer from the UK has looked at the problem
and he thinks, at the moment, that 22-23 pf will probably do the job. I'll post
the results for others who encounter this problem.
Ron
On Oct 3, 2011, at 2:07 PM, Garey Barrell wrote:
Ron -
I've not seen an answer to your question. I don't "KNOW" the answer, but the
crystal in that oscillator is operating in the parallel resonant mode, (not typical for
solid state circuits,) and about 95% of parallel resonant crystals are specified for a 32
pF load. I have seen a few spec'd for 20 pF load, but not sure why.
Anyway, I suspect ICM will be able to tell you what is correct, or may be able
to calculate from the schematic. At worst you could specify 32 pF and see what
happens! The effect of incorrect load is a frequency deviation, and L1005
gives 'some' range of adjustment.
Let us know what you find!
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>
Ron Ries wrote:
Hi All,
i have posted this request several places on the internet and tried to listen
in to the Drake Tech Net but couldn't connect.
I am restoring a Drake TR-7A and the 13.695 MHz VCXO crystal has drifted way
off frequency. I am trying to have a new made at ICM.
I also have ordered on from John Kriner but need the following information:
What is the load capacitance for this crystal in the VCXO application?
Thanks!
Ron
KK7KZ
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