Why do I have no RF output?

This could be caused by a number of variables including: defective SPA and/or DMOD, filter board is programmed wrong, coupler is not tuned, or the antenna is defective.

To isolate the problem, it is necessary to remove the coupler and antenna from the system. Refer to Section 2 of the technical manual and find the Transmitter Diagram (DWG 4792). Turn off input power and turn the RF switch to OFF. Move the blue wire from TB3-3 to TB3-2. This places the RF output onto the two gold resistors mounted to the front panel. These two resistors are the internal dummy load and will act as an antenna for trouble shooting purposes.

NOTE: The internal dummy load is not designed for continuous operation. Limit full power operation to fifteen (15) minutes.

Reapply input power and turn the RF switch back to on. Place the MONITOR switch in the DSBL position to prevent the transmitter from shutting down. SLOWLY increase the RF level pot. While increasing the RF level, pay close attention to the PA volts, PA current, and reflected power. Do NOT allow reflected power to exceed 30% or the PA voltage to exceed 90 volts.

The PA voltage and current should be as follows:

• For a 25-watt transmitter: 25 to 45 volts and 0.8 to 1.3 amps.
• For a 50-watt transmitter: 35 to 55 volts and 1.1 to 1.6 amps
• For a 100-watt transmitter: 50 to 80 volts and 1.5 to 2.3 amps. If there is PA voltage and no current, the filter board is not programmed correctly or there is a problem with the SPA or DMOD board. Refer back to step #2 for the filter board. A properly programmed filter board will measure less than 10 ohms from pin 5 to pin 20. Refer back to step #7 for the SPA and DMOD.
• If there is PA current and no voltage, the problem is likely in the DMOD board (possibly the SPA). Refer back to step #7 for troubleshooting the SPA and DMOD.