Elecraft K1 - Manual (Page 88)

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7. Premixer: U7, pin 4 or 5 (whichever is greater). Expected: .04-.25 V.
Actual: _______.
8. Premix band-pass filter: FIL-P1, pin 6. (FIL-P1 is an 8-pin connector on
the Filter board, near the crystals. Pin 6 is the third pin from the right end.)
Expected: .04-.15 V. Actual: _______. (Note: the expected voltage takes
into account the de-tuning effect of the RF probe. The signal level would
be higher if the filter was re-tuned to compensate for it.)
9. BFO: U2, pin 7. Expected: .015-.100 V. Actual: _______.
10. Connect a signal generator or test oscillator to the antenna jack. Set the
signal level to about 0.14 Vrms as indicated by the RF probe, with the
probe tip on pin 8 of FIL-P3 (right-hand end of the 8-pin connector on the
Filter board near the antenna jack).
11. Low-pass filter: FIL-P3, pin 1. Expected: .12-.16 V. Actual: ______.
12. T-R switch: FIL-P2, pin 8 (P2 is the front-center 8-pin connector on the
Filter board). Expected: .07-.12 V. Actual: _______.
13. RF band-pass filter: FIL-P2, pin 1. Expected: .06-.13 V. Actual: _____.
14. Attenuator and T1: U1, pin 1. Expected: .40-.70 V. Actual: ______.
15. Receive mixer: U1, pin 4. Expected: .50-.80 V. Actual: _______.
16. Post-mixer amp: R14, right end. Expected: .50-.80 V. Actual: ______.
17. Connect a pair of headphones or a speaker and adjust the AF GAIN so that
you can just hear some background noise. Tune the VFO until you can hear
the signal from your test generator peaked in the crystal filter. Since AGC
is turned off, the signal may be extremely loud and will probably be
clipping (distorted) at the AF output.
18. Crystal filter: U2, pin 1. Expected: .30-.50 V. Actual: _______. (Re-peak
the signal using the VFO as needed.)
19. Disconnect the RF probe from the DMM.
20. Set up the DMM to read AC volts, 20 or 30-V meter range. Connect the (-
) lead of the DMM to one of the ground test points using an alligator clip.
The (+) lead will be touched to the points indicated in the following steps.
21. Product detector (saturated output): U2, pin 4. Expected: .40-.80 V (AC
rms). Actual: _______. (Re-peak the signal using the VFO as needed.)
22. AF preamp: U3, pin 5. Expected: 2-4 V. Actual: _______.
23. AF amp: U4, pin 6. Output voltage should vary from 0 to about 4 or 5 V
as the AF GAIN control is varied.
Transmitter Signal Tracing
In the following steps an RF probe is used to determine where the transmitted
signal is getting lost or attenuated. These checks are made from the bottom side
of the RF board so that the Filter board can be left plugged in. Each transmit
test point is clearly labeled, with a small arrow pointing to the appropriate PC
board pad. You’ll want to refer to the transmitter schematic (K1 RF Board,
sheet 2) as you perform the measurements.
1. Do the VFO and receiver signal tracing first to check VFO/premix signals.
2. Connect a dummy load to the antenna jack.
3. Turn the K1 upside-down and remove the bottom cover.
4. Install a very short jumper from the point labeled DRV to ground. This
allows measurement of all low-level transmit stages.
5. Turn on the K1 and switch to the desired band. Set the power level to 3
watts using the OUT menu entry.
6. Connect the RF probe’s ground clip to the ground jumper on the bottom of
the RF board, near the center. Connect the RF probe’s output to the DMM,
and set the DMM for DC volts (2 or 3 V scale).
In the remaining steps, touch the RF probe tip to the indicated points and enter
TUNE mode to take a reading. (Hold WPM+/WPM- together to activate
TUNE.) Cancel TUNE after each reading by tapping any other switch.
Note: Do not key the transmitter for more than about 10 seconds at a time.
7. PRE (premix): Expected: .04-.09 V (DC). Actual: _______.
8. ATTN (TX attenuator): Expected: .02-.05 V. Actual: _______.
9. OSC (TX 4.915 MHz): Expected: .01-.04 V. Actual: _______.
10. MIX (TX mixer): Expected: 0.1-0.2 V. Actual: _______.
11. BUF (TX buffer): Expected: 1.5-2.0 V. Actual: _______.
12. TR1 (first TX T-R): Expected: 0.5-1.0 V. Actual: _______.
13. BPF (band-pass filter): Expected: 0.5-1.0 V. Actual: _______.
14. TR2 (second TX T-R): Expected: 0.5-1.0 V. Actual: _______.
15. TR3 (receive signal shunt): Expected: < .01 V. Actual: _______.
16. Remove the short from DRV to ground. Set DMM scale to 20 or 30 V.
17. DRV (driver): Expected: 0.9-1.6 V. Actual: _______.
18. PA (power amp): Expected: 10-15 V. Actual: _______.
19. ANT (low-pass filter): Expected: 10-12 V. Actual: _______.
20. Disconnect the RF probe. (The last measurement is DC volts, not RF.)
21. RFD (RF output detector): Expected: 1.7-2.0 V. Actual: _______.