You have a failed power supply/ Almost certainly the main switch Q1 a MOSFET. This can also take out the feedback transformer T2 which is a PITA. You can ty DC input, see /g/HP-Agilent-Keysight-equipment/message/151023 for the connector detail, its the same on SA and 8920x. Better to use 24V if you have it the current is high at 12V. If it doesn't run on DC it is probably Q1. The DC input runs a DC-DC converter with high voltage DC output. If it runs on DC it is likely the mains bridge rectifier. A failed Rifa is possible but unlikely as they self heal and you can't miss the smell.... Join the 8920 group too /g/HP8924-Family-Spectrum-Analyzers/topics
