Rob,
There is either too much inductance or too much capacity in the VFO
circuit - the high voltage means that the K2 is trying to reduce the
capacity to bring things into line.
Count the turns on T5 very carefully. Each wire through the center
counts as one turn - a full wrap around the core equals 2 turns.
If the T5 turns are correct, spread the red turns of T5 out as much as
possible to see if that resolves the problem.
Worst case, you may have to remove a turn from T5.
BTW, if you discover an extra turn on T5, you might want to count the
turns on the other toroids you have wound to be certain they contain the
right number of turns. Winding an extra turn on toroids is not uncommon
for builders with limited experience in winding toroids.
73,
Don W3FPR
On 9/28/2013 4:16 PM, Rob Gault wrote:
K2 #7449 VCO alignment difficulty.
Cannot get 4.0 MHz R30 voltage to change at all - it measures 7.97V. Have
confirmed all the cap values, varicap diodes are correct parts, T5 wound
and wired correctly.
Have scoped the area comparing to a second operational K2 & the wave forms
look and behave the same as the rigs are tuned. The voltage on R30 is
simply too high at 4.0 MHz.
I set the K2 to 3.5MHz and adjusted L30 for the lowest voltage, this gave
the following results:
3.50 4.14 4.00 7.97
7.00 4.39 7.30 6.30
10.00 5.08 10.15 5.86
14.00 3.84 15.00 5.98
18.00 4.42 18.20 4.67
21.00 3.83 21.45 5.38
24.80 5.92 25.00 6.40
28.00 4.64 28.80 5.66 (29.70 6.87)
Should I continue the build or what else should I check?
THANKS & 73, Rob KC2VMP
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
