21
2-2-1, VOX TEST SETUP
Warm up in “safe” mode. Tune up in cw mode
•
Set up; MOX, AM, MIC GAIN to 0, DELAY min, VOX to min. ANTI TRIP to min.
•
Insert dummy mic plug. (This will mute the TX in the CW position.)
•
Connect mic patch cable. Set audio oscillator to 1400Hz minimum output.
•
With no audio input key up in mox, am and adjust T2 for 100 watts output.
•
Set the MIC GAIN to 8. Monitor the RF carrier with the scope.
•
Key the mic and increase the output of the audio oscillator until you have 95% modulation.
•
Switch to CW, leave all settings and controls as they are this is the setup for 2-2-2 tests.
2-2-2, VOX TEST
In the following tests we will be switching between CW and AM. The CW position will be the rest mode and
AM will be the test and measurement mode.
•
Switch to VOX, AM and advance VOX control R80 until the transmitter keys up. Switch to CW.
•
Check the rotation of VOX control.
1, Control in the center third of its rotation is normal.
2, Control in the lower third of rotation indicates component drift or gassy tube in the VOX train.
3, Control in the upper third of rotation indicates component drift or weak tube in the VOX train.
•
Leave all controls on the HT-44 as they are for the next series of tests.
If the VOX fails to operate properly there is a fault in the vox train. Insure the controls are set per 2-2-1 and
proceed to 2-2-2-1. Once the fault is cleared return and complete 2-2-2.
2-2-2-1, VOX SIGNAL & VOLTAGE MEASURMENTS
Turn the RF LEVEL to zero and with the rest of the controls set as per section 2-2-1 switch to VOX. Using the VOX control
to key and unkey the unit. Make and record the following measurements.
MEASURED WITH SCOPE
MEASURED WITH DVM
TIE POINT OF R80 & R81
V13A pin 7
V14C pin6
V13B p3 V14C p3
V13B pin 1
50
–
75mvpp
1.5
–
2.5 vpp
30vpp
0 / 15vdc *
305 / 169vdc *
NOTE * When VOX is operating correctly the first voltage is UNKEYED the second is KEYED.
The first incorrect measurement is the location of the fault. Return to 2-2-2 when fault is cleared.