PK-232 TECHNICAL MANUAL
CHAPTER 7 – TROUBLESHOOTING
PK232TM Rev. A 5/87
7-4
Page 43
7.3.2.
Symptom: Modem cannot be calibrated
If the calibration signalis present, but you cannot seccessfully calibrate the frequency, the
value of a frequency-determining component may have changed.
o
Attempt the calibration procedures presented in Chapter 6.
o
Verify that the proper signals are present at U40 pin 2.
o
Verify the signal frequency with a frequency counter.
o
verfiy the values of the appropriate passive components.
7.3.3.
Symptom: Transmitter cannot be keyed
If the transmitter cannot be keyed and the
DCD Threshold
control functions normally
and causes the
DCD LED
to be lighted or extinguished:
o
The problem may be in the watchdog timer circuit at Q10 and Q3, or the PTT driver
transistors Q4 and Q5. Verify timing capacitor C55.
If
DCD Threshold
control has no effect on the
DCD LED
and the LED is permanently
lighted:
o
The problem may be in the DCD Threshold circuits at U34. Verify variable resistor
R136 for an open lead.
7.3.4.
Symptom: Transmitted signals not copyable by other stations
If other stations are unable to decode your transmissions when using FM:
o
Verify the associated transmitter's modulation index. Verify that peak deviation at
any tone does not exceed 4 kHz.
o
Adjust the AFSK output level with R155 to produce the correct transmitter deviation.
If other stations are unable to decode your transmission when using an SSB transmitter:
o
Verfiy that the transmitter's audio input stage and ALC systems are not being over-
driven.
o
Adjust the transmitter's microphone gain in accordance with the radio manufac-
turer's duty-cycle, plate current and power dissipation specifications.
o
If reducing the radio's gain control does not solve the problem adjust the AFSK out-
put level with R155 to produce the correct transmitter operating conditions.
7.3.5.
Symptom: Received signals not copyable
If unable to correctly decode signals from other stations:
o
Perform the calibration procedures presented in Chapter 6.
o
Verify the correct settings of variable resistors R81 and R96.
o
Verify that the DCD Threshold control is operating correctly.
If the calibration procedure is satisfactory:
o
Inject a 1200-Hz test tone into J3 or J5.
o
Verify audio signal flow through switch SW2, C54, R34, U28-14 and U28-7.
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