Specifications

Page 17
Copyright 2006 Robert A. Larson, KC9ICH
ALIGNMENT AND TROUBLESHOOTING
The alignment procedures presented in this section are routine touch-up procedures for all tuned circuits and other adjustments. It is
recommended that the procedures be performed in the order presented. However, if complete realignment is not required (as may be
the case when just one tube is replaced), perform just those procedures required. Refer to Figures 6 and 7 for component placement.
RECEIVER ALIGNMENT
Receiver alignment involves only the adjustment of the Second IF coil. The RF coils which affect receiver performance are also used
in the TRANSMIT mode. Their adjustment is covered under “TRANSMITTER ALIGNMENT”.
1) After allowing approximately five minutes for warm-up, tune the receiver to the middle of the band and on a “clear”
frequency.
2) Adjust the P.A. TUNE, P.A. LOAD, and PRESELECTOR for maximum noise.
3) Adjust the second IF coil (L801) for maximum background noise.
S-METER ADJUSTMENT
With the antenna disconnected, R.F. GAIN control fully clockwise, and S-Meter switch in S-METER position, set R705, (S-Meter
zero), located on the rear panel, for zero meter reading. Determine that no local signals are being received.
TRANSMITTER ALIGNMENT
1) To adjust the Power Amplifier Bias (after allowing approximately five minutes for warm-up):
a) Hold Meter Switch in P.A. CATHODE position.
b) Rotate CARRIER INSERTION control fully counterclockwise.
c) Rotate Mic Gain control fully counterclockwise, then key the transmitter with the microphone switch. Adjust the Carrier
Balance control, R1309 on the bottom cover, for a null.
d) Again, key the transmitter with the microphone switch, and without speaking into the microphone, adjust the P.A. BIAS
control on the rear panel until the meter reads 40 mA of idling current. This point is indicated on the meter by the small
triangular “delta” symbol.
2) The alignment of transmitter circuits involves the adjustment of tuned circuits in the VFO Amplifier, V1, the Transmit MIXER,
V2, and the DRIVER stage, V3. It is recommended that a 50 ohm dummy load be connected to the antenna jack during this
series of adjustments
a) Set the tuning dial to approximately 28.5 MHz, and the PRESELECTOR control at 12 o’clock.
b) Set P.A. LOAD control to 9 o’clock.
c) Set Meter switch to P.A. CATHODE.
d) Press Mic button. Check idling current. It should be on the “delta” symbol when the CARRIER BALANCE control is
nulled, and the CARRIER INSERTION control is fully counterclockwise. Adjust P.A. BIAS control, on rear panel if
necessary.
e) With Mic button depressed, adjust CARRIER BALANCE control for slight increase in meter reading, (50 to 60 mA.).
Adjust P.A. TUNE control to resonance (dip).
f) Adjust coils L10
1, L201, and L301, for maximum reading. When reading goes higher than 80 mA., or so, adjust CARRIER
BALANCE control for 60 mA. again.
g) Adjust coils carefully for maximum peak. Exercise caution with CARRIER BALANCE control. Do not exceed 100 mA
reading for more than a few seconds. Be sure P.A. TUNE control is resonated (adjusted for “dip” in meter reading).
3) Power Amplifier Neutralization.
a) After allowing approximately five minutes for warm-up, tune transmitter to approximately 28.5 MHz.
b) Set the P.A. LOAD control to 9 o’clock.
c) Set S-Meter switch to P.A. CATHODE.
d) Key the transmitter with the Mic button, and without speaking into the microphone, adjust the CARRIER BALANCE
control for a reading of approximately 100 mA. Quickly adjust the PRESELECTOR for a peak. Quickly readjust the
CARRIER BALANCE control to 100 mA. if it increased to a higher reading.
e) With the Mic button still depressed, rotate the PA. TUNE control through its range from 9 o'clock to 3 o'clock. You will
note a pronounced dip in meter reading at resonance. Observe any tendency for the meter to “peak” above the 100 mA.
plateau on either side of resonance. If there is such a peak, adjust C101, the P.A. NEUTRALIZING trimmer, to suppress the
peak. When properly neutralized, the meter reading will hold steadily at 100 mA. except for the sharp dip at resonance, but
there will be no peak above the 100 mA. level.
f) Key the transmitter with the Mic button, and readjust the CARRIER BALANCE control for minimum Power Amplifier
current. Power Amplifier idling current should be on the “delta” symbol. If not, repeat the Power Amplifier Bias
adjustment described in TRANSMITTER ALIGNMENT, STEP 1.
4) Carrier Frequency Adjustment. A dummy load, wattmeter and audio generator are required for this adjustment.
a) After allowing a five minute warm-up period, tune the transmitter to approximately 28.5 MHz with the Mode Selector at
USB.
b)
Key the transmitter with the Mic button, and adjust the CARRIER BALANCE control for minimum Power Amplifier
current.
c) Insert a 1500 Hz audio signal from an audio generator into the MIC jack on the front panel. Adjust the gain of the audio
generator and the MIC GAIN control (R1404) until the wattmeter reads approximately 10 to 15 watts.