Before printed circuits, solder was used only to provide electrical connection, not mechanical support. In the 60's manufacturers learned how to stuff a through-hole board with every component they could get made for it and run it over a wave of molten solder. The conveyor speed and solder bath temperature got adjusted to compromise between overheating a tiny germanium diode and getting solder to stick to the 12-gauge plated steel mounting pin of an open frame relay.

The relays lost. Of course they looked OK at the time, but those outfits building high-reliability equipment (medical, aeronautics, space) could see further into the future, and at the very least hand re-touched the big heat sinkers like our Bosch relays, just like we do now.

So it is really easy for you to make these work again. Just look for the big heavy objects on the circuit board, where the only mechanical attachment is the solder itself.
--
Art Benstein near Baltimore

Generally speaking, you aren't learning much when your lips are moving.