The coupler will not tune.

Refer to section 5, Coupler Setup, of the technical manual.

To begin with, do NOT turn up the power on the transmitter to more than 20 PA volts. This can damage the transmitter. Turn the RF pot fully counter-clockwise (CCW). Make sure that the transmitter is in the carrier mode (CARR on the mode switch). Set your monitor switch to the DISABLE position.

1. Take an oscilloscope and tape the probe to the enclosure of the antenna coupler. The probe should be approximately 2 inches from the output. The probe should not be attached to anything; the readings will be "off the air". Note that these readings are a visual representation only. This is looking for the maximum signal size to tune the coupler. This is not intended for measurements.
2. Turn the fine taps and impedance transformer switches to position six (6) respectively. Place the set-up/run switch on the Auto-tune board to SET-UP. Apply power to the transmitter and slowly increase RF power to approximately 15% forward power. Do not exceed 20 PA volts.
3. Refer to the signal on the oscilloscope and center the Vernier knob at the 12 0’clock position.
4. Change the fine taps switch one position at a time. Note which direction the fine taps switch is turned when the signal increases. If the signal is still increasing and the fine taps switch is at the end, power down and change the coarse taps setting. Repeat this step until the maximum signal is attained.
5. When maximum signal size is attained through a combination of coarse and fine taps, tune the Vernier knob by hand for maximum signal strength.
6. Set the set-up/run switch on the auto tune board to run.
7. While monitoring the tune meter (switch in the tune position), turn the impedance transformer switch until the reading is minimal. The reflected power reading should be very small.
8. If everything checks out OK, turn up the RF power to 100% forward power, set the monitor switch to reset and then to enable. Place the mode switch to IDENT.