Elecraft K2 Owner's Manual - Manual (Page 163)

11
BFO (RF, sheet 2)
1. BFO Output: Measure the signal on U11, pin 6 (NE602). Expected:
0.20-0.70 Vrms. Actual: ______.
2. Use the menu to select C A L F C T R . Press EDIT again to confirm; the
display will now show a frequency reading (it will depend on where you
have the frequency counter probe connected).
3. BFO Buffer Output: Measure the amplitude of the signal at TP2 using
the RF probe. Expected: 0.025-0.070 Vrms. Actual: _______.
4. Exit CAL FCTR . Check the BFO frequency (RF Board, Alignment
and Test Part II).
Low-Pass Filter, Bandpass Filter, and T-R Switch (RF, sheet 3)
1. Turn both the attenuator and preamp OFF using
P R E / AT T .
2. Set RF GAIN to minimum.
3. Set AF GAIN to about 10% and connect a pair of headphones.
4. Switch to the 30 m (or the correct band for your signal generator).
5. Connect a signal generator or test oscillator to the antenna jack. Set the
signal generator for 0.14 Vrms as indicated by the RF probe.
6. If possible, tune the VFO until you hear the signal. It may be quite strong
even if your receiver is attenuating the signal somewhere. Find the
approximate signal peak by ear. Set AF GAIN to minimum.
7. Align the band-pass filter for the current band if possible: (a) Put the RF
probe on the banded end (cathode) of D6 (to the left of the I/O controller,
U1); (b) adjust the band-pass filter for the current band for a peak
indication on the DMM (on 30 m: adjust L8 and L9).
8. Aligning the band-pass filter may have changed the input impedance of
the receiver. Put the RF probe back on the antenna input and adjust the
signal generator for 0.14 Vrms again.
9. Low-Pass Filter Output: Measure the signal at jumper W1, near the PA
transistors (Q7/Q8). Expected: 0.13 Vrms. Actual: _______.
10. T-R Switch #1 Output: Measure the signal at W6, which is just to the
right of the transverter/60 meter option connector, J13 (near the back
edge of the board). Expected: .093 Vrms. Actual: _______.
11. Band-Pass Filter Output: Measure the signal at the left side of D6.
Expected: .086 Vrms. Actual: ______.
12. T-R Switch #2 Output: Measure the signal at the right side of D6.
Expected: .077 Vrms. Actual: ______.
Mixer, I.F. Amplifiers, and Crystal Filter (sheet 2)
1. Attenuator Off Test: Measure the signal at the end of R72 closest to
Q21. Expected: .077 Vrms. Actual: _____.
2. Preamp Off Test: Measure the signal at the end of R73 closest to Z6.
Expected: .077 Vrms. Actual: _____. (Preamp gain will be tested later.)
3. Composite Mixer Output: Measure the signal at the right end of R80.
Expected: .079 Vrms. Actual: _____.
4. Post-Mixer Amp Output: Measure the signal at the case (collector) of
Q22 (2N5109). Expected: 2.20 Vrms. Actual: _____.
5. -5 dB Pad Output: Measure the signal at jumper W2, near the crystal
filter. Expected: 1.40 Vrms. Actual: _____.
6. Crystal Filter Output: Touch the RF probe to jumper W3, near the
crystal filter. Adjust the VFO for a peak in the DMM reading. Expected:
0.35 Vrms. Actual: _____. If this reading is low, it may be due to a non-
optimal setting of the BFO in CAL FIL. Try a different BFO setting, then
adjust the VFO for peak again and re-measure the filter loss. (Note: this
measurement exaggerates the filter loss because the input to the filter is a
composite of many signals besides the desired one.)
7. T7 Step-Up Ratio: Measure the signal at U12, pin 4 (MC1350).
Expected: 0.4-0.8 Vrms. Actual: _____. Note: Limited by D40-D41.
8. I.F. Amp Saturated Output: Measure the signal at U12, pin 8. It may
be anywhere between 0.00 and 0.30 Vrms. Adjust the signal generator
level until the DMM reads approx. 0.15 Vrms. (If your signal generator
is running from a 9-V battery you may have trouble getting the output
this high. Try running the generator from 12V or more in this case.)
9. 2 nd Crystal Filter Output: Measure the signal at U11, pin 1 (NE602).
Expected: approx. 0.27 Vrms. Actual: _____.
10. Product Detector Saturated Output: Measure the signal at U11, pin 5
(NE602). Expected: 0.58 Vrms. Actual: _____.
AGC (Control Board)
1. Disconnect the RF probe from the DMM. Connect the DMM’s (-) lead to
chassis ground.
2. Turn the signal generator completely OFF (remove its power).
3. Set RF GAIN to maximum.
4. No-Signal AGC, Max. IF Gain: Measure the DC voltage on pin 1 of U2
(LM833). Expected: 3.6 V. Actual: _____.
5. Set RF GAIN to minimum.