Populating the PCBs

PCBs are marked according to the original schematics. On some boards the designators were missing. In this case we assigned them our own designators. All PCB designatos have suffixes in order to make identification easier (for example, R1x, where 'x' is the suffix). Here is the list of board suffixes:

  • 284 - 'a'
  • 283 - 'b'
  • 211 - 'c'
  • 205 - 'd'
  • 182 - 'e'

Power supply components have letter 'p' in their designators.

Components without suffixes are off-board components in the original module. In our PCBs they are mounted on board as well.

Heatsink for the 2N3055 power transistor should be mounted on the 5mm standoffs. Install standoffs first, screw the heatsink and the transistor to the standoffs secont. After that solder transistor wires to the PCB. Mke sure you have good connection between transistors enclosure and PCB trace that goes to one of the fixing screws. Use lock washer to ensure good contact.

 IMPORTANT! Before installing RV1b trimmer put its wiper in the middle position.

Here are several guidelines that will help you working with PCBs:

  • Start with smaller components first and move to the bigger ones when all small components are fitted. For example, resistors are often the smallest components (height-wise). You start with all the resistors, then move on to capacitors, after that you put in transistors, trimmers and power components. Inductors and heatsinks are often the last.
  • ALWAYS measure resistors before soldering - no exeptions. Cross-check with BOM and schematics. If in doubt use the value provided in the schematics.
  • When fitting the regulators with heatsinks use the following order:
    • Screw the regulator to the heatsink. Do not use any silicon pads - the heatsinks are isolated from the rest of the circuit.
    • Insert the assembly into the PCB.
    • Solder the heatsink FIRST.
    • Solder the regulator SECOND.
    • If you ever need to replace the regulator, do not remove the heatsink from the PCB. Unscrew the failed regulator and desolder it. After that screw the replacement part to the heatsink and only then solder it to the PCB. This is to make sure there is no mechanical stress on the regulator.

When all PCBs are populated, we can move on to the most interesing part - Switches.