Yaesu FT-991A Technical Supplement

Also see for FT-991A: Information for Customers Operating Manual Information for Customers Operating Setup Instruction manual

Contents

AlignmentALIGNMENT-15 FT-991 Technical SupplementDrive Stage Idling Current Adjustment Connect the DC ammeter to J4506 on the V_U-PA Unit. Press and hold the PTT button, while adjustVR4502 so the DC ammeter reading is “100 mA(±10 mA)”. Release the PTT button. Disconnect the DC ammeter from J4506. Re-connect the red cable to J4503 on the V_U-PA Unit.Semi-Final Stage Idling Current Adjustment Connect the DC ammeter to J4507 on the V_U-PA Unit. Press and hold the PTT button, while adjustVR4505 so the DC ammeter reading is “600 mA(±50 mA)”. Adjust VR4506 so the DC ammeter reading is“1.2 A (±0.1 A)”. Release the PTT button. Disconnect the DC ammeter from J4507.Final Stage Idling Current Adjustment Disconnect the red cable from J4503 on the V_U-PA Unit. Connect the DC ammeter between J4503 andred cable. Press and hold the PTT button, while adjustVR4503 so the DC ammeter reading is “800 mA(±50 mA)”. Release the PTT button. Disconnect the DC ammeter from J4503 and redcable, then connect the red cable to J4503. Disconnect the 50-Ohm resistors from J4501and J4502, then connect the coaxial cables toJ4501 and J4502. Re-connect the jumper plugs to J4505, J4506 andJ4507.V_U-PA Unit TX Adjustment Set the VFO-A frequency to 439.990 MHz in theUSB mode. Connect the 50-Ohm Dummy Load and Watt-meter to the “144/430 MHz” ANT jack. Connect the Audio Generator to pin 5 of theMIC jack (pin 4: GND), then set the output levelto 0.5 mV @1 kHz. Press the PTT button, then adjust the MIC gainto set the RF Power output to 25 W on the Watt-meter. Press the PTT button, adjust TC4501 for maxi-mum deflection on the Wattmeter. Release the PTT button.VR4502 VR4506J4506J4507 J4503VR4505VR4503J4501J4502J4505 TC4501