If I'm reading this right, HETL toggles the generator from low band to high band. When it toggles to low band, mixer U201 heterodynes the difference between 800-1045 MHz and 800 Mhz to create the frequencies below 245 MHz and that get's routed to the output.
It sounds like the game plan is to confirm good 15 VDC going to Q202, Q204, Q206, Q207 and Q301. After that check that 800 MHz is being produced at TP5.
My scope max's out at 300 MHz. Any creative ways to check 800 MHz other then purchasing a high end frequency counter?