Well, the SG503 that I replaced the front panel on works great, except the 100-250MHz range...
It's range is currently low at 87.2-230MHz...
I've rebuilt the variable cap, replaced all the drifted parts with new, given is a spit shine, etc etc, but there isn't much adjustment for this range to bring it into spec.
One thing I think may be an issue is that I replaced some drifty carbon composite resistors but used metal film, so I'm wondering if they are messing things up with parasitic capacitance/inductance.
(R145, R146, R150 center left of the schematic)
I think I might try replacing them again but use large SMD resistors to get something more non-inductive etc. I'm pretty certain I don't have any 1/8W 51R carbon composite resistors in my stock, and the store in Akihabara with them only sells 1/4W and above from memory.
I also need to go get some realllly thick grease for the reduction gear assembly on the frequency adjustment dial, the thinner standard grease I used makes for a notchy feeling.