I finished refurbishing the KG-686 and hooked it up to a frequency counter. The RF Signal for the AM band was perfect--no alignment needed. BUT, the AM is band "B" on the dial and I had to set the band switch knob at band "E." I don't have the assembly instructions, and it would take me quite a long time figure it out from the schematic.
So I put it away the KG-686 for now and pulled out a Knight (no model) RF Generator. This is an older one--a proper one with vacuum tubes. There's no model name or number anywhere on the inside or outside, but it seems to be identical to the schematic for the KG-650.
My first problem with this one is that the on-off-fine attenuator switch is absolutely frozen. I tried greasy tuner cleaner and penetrating oil without success. It feels like it's a mechanical obstruction rather than corrosion. I thought the problem might be in the on-off part of the switch, but when I took it apart the on-off worked fine and the potentiometer shaft still wouldn't turn.
The schematic says that this is a 1K pot, but between the end terminals I get 30K ohms, and 2.3K ohms from the sweep to either end.
Is this thing repairable? If I try to disassemble it further I may not be able to get it back together again (Humpty Dumpty Syndrome).
Can I replace the switch with a toggle and a 1K pot? I have 1K ohm/500v pot and some 125v/3 amp toggles.