Understanding the baseline performance is critical when verifying if a unit is within factory spec: Factory Specification Triple-conversion (SSB/CW/AM) / Double-conversion (FM) 1st IF Frequency 69.450 MHz Output Power 100W (SSB/CW/FM), 25W (AM) Supply Voltage 13.8 VDC ±15% (Negative Ground) Current Drain 2.0A (RX), 23A (TX max) Common Troubleshooting & Maintenance Tips
: Full circuit diagrams and board layouts for both "Side A" (surface-mount components) and "Side B" (leaded/mixed components). Parts List yaesu ft-891 service manual
On the Main Unit schematic, look for the “FWD” and “REF” test points. The service manual provides nominal DC voltage values at full power (e.g., 2.5V at 100W forward). 2.5V at 100W forward).