Sounds to me like that pretty fragile RFC15 (E690013) has opened. Scott
([EMAIL PROTECTED]) can get you a new one right away.
Brian, W6FVI
Bill Acito W1PA wrote:
Update.
1. Tom (N0SS) suggested I redo the CAL PLL. Done. No effect.
2. Jim (K4ZM) suggested I....
Check the resistance of the small 100uh rfc that you added between 16
and the +12 volt line. I have seen this same problem when that RCF
is open. It is a very delicate choke and very easy to break the wire
inside the choke. An easy way to test it is to measure the dc voltage
on both sides of the rfc and if the voltage is not the same then you
probably have a bad RFC.
..so I popped the bottom and took a look. On the rail (which is not
12v, btw), I read 5.02V,
and on the other side of the 100uH I read 4.23V... not the "same",
but I assume that's the
choke wire resistance. Along the same vein, I also remembered that
someone else attributed
this issue to the added LC circuit (as part of the A-B version update):
http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-08/msg00424.html
So I took the blade of my screwdriver and shorted the 100uH inductor
(RFC15).... warble is gone!
So, questions:
Are the L-C comps "hard-linked"? i.e. if I remove this mod, is there
any benefit to leaving the cap,
or should I remove both parts? Should I try a different 100uH instead?
I don't think I ever had the
7128 warble, so I installed these as a precaution only.
Any ideas on why this LC circuit is the culprit (might want to look at
this since there is at least two confirmed cases now)?
As Wayne suggested in the included link, I also checked the value of
R19 and it was fine.
Bill
W1PA
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