Service manual

STP 11-25R13-SM-TG
3 - 13
Performance Measures Results
9. Connect the transmitter output to a dummy load and close the main circuit breaker to
apply AC power to the transmitter and initiate the up-cycle.
P F
10. After approximately 5-minutes warm-up time, verify that all lamps illuminate. P F
a. The AC lamp indicates the main circuit breaker is ON, applying AC power to the
up-converter.
P F
b. The filament lamp indicates the presence of AC power applied to the filament
transformer.
P F
c. The high voltage lamp indicates the presence of AC power applied to the high
voltage transformer.
P F
d. On the up-converter, the transmit lamp illuminates when the up-cycle is complete
and the system is in transmit status.
P F
11. Log the elapsed time indicator reading, the amount of time filament voltage is applied to
the final amplifier tube and a reference for maintenance and tube changing.
P F
12. Verify that all fans are operational; if not, check the fan protection fuse. P F
13. Observing the up-converter meter, select meter switch settings and log readings. P F
a. At +12 V, record the value and presence of the +12 VDC power supply. P F
b. At +26.5 V, record the value and presence of the +26.5 VDC power supply. P F
c. At OSC TP (3 V), record the value and presence of the oscillator test point. A mid-
scale reading is an acceptable value.
P F
14. Observing the high voltage (HV) power supply meter, select meter switch settings and
log readings.
P F
a. At FIL VOLTAGE FINAL, record the filament voltage applied to the tube, 5.5 VDC
nominal.
P F
b. At CATHODE CURRENT FINAL, record the cathode current (no RF drive), 350
ma nominal.
P F
15. Apply a 1 V P-P (140 IRE) video signal to the input from the VTSG. P F
NOTE: Follow the manufacturer's manual procedures for video and audio adjustments.
16. Observing the modulator meter, adjust audio and video modulator modules. P F
a. Select the video position and adjust the video level control for a reading of 87.5
percent.
P F
b. Select the audio position and adjust the aural deviation control for a reading of +/-
25 kHz.
P F
17. Observing the up-converter meter, select meter switch settings and log readings. P F
a. At PEAK VISUAL POWER, adjust the POWER CONTROL to obtain a reading of
100 percent. This adjusts the gain of the up-converter and thereby sets the overall
composite output power.
P F
b. At AVERAGE AURAL POWER, verify a reading of 100 percent power. P F
c. Verify that broadcast power is within FCC tolerance or host nation established
limits; adjust if necessary.
P F
18. Observing the HV power supply meter, select meter switch settings and log readings. P F
a. At CATHODE CURRENT FINAL, record the cathode current (RF drive applied),
500 ma nominal.
P F
b. At B+ VOLTAGE FINAL, record the B+ voltage of the final power amplifier.
Nominal plate voltage value is 2 kV.
P F
19. Measure carrier frequencies. P F
a. Measure the audio carrier frequency with a frequency counter at the test point
shown in the manufacturer's manual.
P F