Hi Chris
John is right. Luckily there are two other working LPF circuit blocks do use for reference. In answer to other question Q5 is probably OK and L9 would not be open if DC switching properly.
Must be certain DC is OK before worrying about RF. If it were me I’d remove L9 choke again and verify that DC is then failing - excludes a solder bridge bypassing the choke. Or measure RF on both sides of choke - should be a reasonable differential.
Make sure the input diode has been tested or replaced. May be open on forward bias.
Assuming RF is getting into the LPF and choking is good at L9, RF must be being either shunted or attenuated in the LPF.
Measuring RF at centre of LPF compared to input and output may be clue.
Remove and inspect and/or maybe jumper the toroids to see effect on RF levels? ?Using low power supply and dummy load should be not much risk to finals.
-Nick
