Dear Friends,I am in the process of building my serial# 6614 K2 (the 3rd one
that I have built since 2000), and run into a problem during the VCO testing:
First, the PLL reference Oscillator test checked within specs, but in the next
(VCO) test, while checking at TP1 with the frequency counter,with the K2 at
4.000.10Khz, I am measuring a 7.59 to 7.60Mhz with the last digits of the
reading rapidly alternating. The DC voltage at the left end of R30 is about
5.3V with some spontaneous fluctuation, and not responding to adjustment of the
L30 as per the VCO alignment test in page 64 of the manual.Reheating the leads
of T5, checking C72 and general check for soldering issues did not reveal
anything. PLL reference oscillator output with the RF probe: Pin 1 of U4 1.08V
(ok), but VCO output signal (pin 3 of U3) 1.13V when only 0.3-0.4V are
acceptable and VCO buffer output (pin 6 of U6) 0.85V with the acceptable range
being 0.6-0.75VDC measurements :Q18G 0.0V (-1.0)S 4.3V (2-3)D 7.1V
(6.3)U3 Pin#1 1,1V (0.0)2 3.9V (4.3)3 3.8V (4.1) U4 Pin#3
3.5V (0.0)7 5.0V (0.0)8 0.06V (0.1) The values in the parentheses are
the acceptable per the manual, and the rest of the IC pins are within specs.
Based on the above, I suspect that for some reason the U4 IC might be the
problem (eventhough I did observe antistatic and overheating precautions), but
since its replacement can be technically difficult and would have to be
posponed until the part arrives from Elecraft to the SV1 land, I would like to
have your opinion as to how I can further troubleshoot this problem before
starting changing parts etc. Thanks, 73Marinos, sv9dru / ki4gin> Subject:
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