11
1-6, DRIVER/PA PRETEST & SETUP
In order to properly test and analyze the audio, phasing and I.F. circuits properly the driver and PA need to be at
or near normal. The 6DQ5 final tubes must be a matched pair. If you are unsure of the conditions of the final
tubes proceed to section
3-1, ERRATA SHEET TUBE MATCHING
and follow the instructions.
1-6-1, DRIVER & PA PRESET
Read through the following procedure to insure you understand all of the instructions before you start
the operations.
Set the switches and controls to the “SAFE” configuration. Attach a microphone. Set the band switch to 40-
meter band. Insure MIC GAIN and RF LEVEL are set to zero. Set the signal generator to 7.23 MHz and max
signal out. (output must be greater than 100,000uv). Using the 1X probe inject the signal from the generator into
pin 2 of V8 (SECOND MIXER). Insure the test meter is connected to the test jacks in the rear of the power
supply. Preset the DRIVER TUNE and the FINAL TUNE for the center of the 40m bar.
Connect wattmeter and dummy load to transmitter output.
•
Watching the plate current on the test meter and the power out on the wattmeter key the mic.
•
Throughout this process do not key the mic for more than 3 to 4 seconds at a time
•
If you have power out adjust the drive from the signal generator for 35 to 50 watts. Keep adjusting the
generator to maintain the output at 35-50 watts throughout this process.
•
If there is low or no power out observe the plate current and adjust the DRIVER TUNE for a plate
current peak.
•
Once the driver is peaked adjust the FINAL TUNE for a
dip
in plate current.
•
Adjust L8 and L18 for max power out.
If you are unable to get a minimum of 35 watts out then you have a fault in V8, 9, 16 or 17, or their associated
circuitry. See section 2-2-4 DRIVER/PA TROUBLESHOOTING. This fault must be cleared before proceeding
see section 2-2-4.
1-6-2, 6.5 MHZ TRAP
NOTE: This is the final adjustment for the 6.5meg trap.
Set the signal generator to 7.00 MHz. Set the RF LEVEL to zero, MIC GAIN to zero. Key the mic and adjust
the DRIVER TUNE and the FINAL TUNE for max power at 7.00 MHz:
•
Readjust the generator for 6.25MHz.
•
DO NOT readjust the LEVEL or GAIN.
•
Key the mic and adjust L11 (6.5MHz TRAP) for
MINIMUM
power out.
If you cannot null the 6.5MHz then either L11 or C59 is at fault. This completes the driver/PA pretest and setup.