I remember changing from filament displays to LED displays. 7 resistors per digit to put in a 4mm spacer between 2 pcb's and solder, and then solder the 8 wires from the existing display on to this sandwich. 470 ohm 1/8W resistors, and the board took 16 displays, along with a few resistors for some of the decimal points, along with some 3mm as colons. Took about 3 days per board to do and test then fix the errors. Then the complaint of too bright, so i did a little thinking and added 2 1N5403 diodes in the common lead to drop the voltage to the display. Not going to unsolder all those resistors and increase them to 680R, way too much paperwork to do.