Yaesu FT-991 Post PA Repair Power Test

The following measurement data was obtained by measuring the output of my repaired FT-991.  HF band RF output data from a known functional FT-991 is provided for comparative purposes.

Test conditions:

• FT-991 processor reset (all settings and parameters default)
• ATU not engaged.
• SWR/Power meter inline to 50 Ohm dummy load
• SWR/Power meter accuracy 10% at full scale.
• PSU 13.8V 50A

Yaesu FT-991 Post Repair idling current at 2A

• FM RF power output test, no modulation
  • 160m 100W, 80m 110W, 40m 110W, 30m 115W, 20m 115W, 17m 110W, 15m 110W, 12m 110W, 10m 110W, 6m 110W
• AM RF Power output test, no modulation (AM RF setting 25W)
  • 160m 30W, 80m 40W, 40m 39W, 30m 30W, 20m 38W, 17m 33W, 15m 35W, 12m 35W, 10m 12W, 6m 31W ALC on all bands when modulated.

Yaesu FT-991 with assymetrical RD100HFF1 failure (Prior to repair)

• FM RF power output test, no modulation
  • 160m 30W, 80m 40W, 40m 80W, 30m 100W, 20m 120W, 17m 120W, 15m 90W, 12m 80W, 10m 110W, 6m 100W
• AM RF Power output test, no modulation (AM RF setting 25W)
  • 160m 1.8W (<2W), 80m <1W, 40m <1W, 30m 1W, 20m 2W, 17m 3.5W, 15m 5W, 12m 6W, 10m 3W, 6m 25W ALC was only observed on 6m only.

The following measurements have been obtained from a known functional FT-991 under the similar test conditions as outlined above.
Yaesu FT-991 functional reference set

• FM RF power output test, no modulation
  • 160m 100W, 80m 120W, 40m 120W, 30m 120W, 20m 120W, 17m 120W, 15m 120W, 12m 120W, 10m 120W, 6m 120W
• AM RF Power output test, no modulation (AM RF setting 25W)
  • 160m 40W, 80m 40W, 40m 40W, 30m 40W, 20m 40W, 17m 38W, 15m 38W, 12m 38W, 10m 30W, 6m 35W  ALC on all bands when modulated.

Note:  The power discrepancy observed between the known functional reference Yaesu FT-991 and the repaired radio, may be attributable to my having set the idling current to 2A instead of the 2.5A as observed on the functional set, the replacement RD100HFF1’s gain or any host of other factors including the accuracy of my watt meter.  I cannot wait to get my hands on the technical supplement to verify the PA alignment parameters.