I have an FRG-7 that is working on AM but no SSB. I was told it’s most likely in the BFO section so I pulled all the parts circled in the attachment. Nothing was bad or out of spec including the 2SK19GR or 2SC372Y.
I’m not sure we’re to look now? I also cleaned the mode switch up real good.
Also checked the following TP’s for voltage not sure if that helps.
TP403 0.0vdc am/ssb,
TP404 2.7 am/ssb,
TP405 0.0vdc am/ssb,
TP406 9.3 am/ 7.7ssb,
TP407 15am/ 14.5ssb,
TP408 10.3 am/ssb.