This is an intermediate to advanced build. If you've not soldered a TSSOP chip before (the DAC), this build may be challenging. Seek assistance if possible.
Everything is marked on the pcb, but if you need help, please see below for parts placement
Solder the DAC first. Use flux. Google some videos if you're not sure how best to solder it.
Do the little voltage regulator next and then check your work on all those tiny pins with a loupe/magnifier.
Save the crystal for last of the smd stuff since it's big and gets in the way of soldering the smaller parts.
There's no direction or polarity here. It can go on either way.
I have been doing the thru-hole stuff in the following order: USB jack, audio jacks, headphone jack, pin headers (2x20 first, then flip over for the 1x20), switches, capacitors, and encoders last. Then do the headers on the display.
The pins here are quite small and close together.
Be extra careful inserting the jack onto the pcb. I've bent the little pins more than once. Before you solder - check from the top with a loupe/magnifier to be sure each hole has a pin in it.
Solder each pin and then hit the area with some flux and touch each point again.
Be aware of the routing on the USB Jack pins. Some pins are tied together, so don't be alarmed if your soldering looks bridged on the diagonals.
Once the USB-C jack is attached, check that you don't have continuity between 5v and GND and then plug power into the jack and check the USB-C power input voltage level. I suggest doing this before you attach the pi. There's a 5v/GND header pin holes right near the voltage regulator which is great for testing voltage (+5v).
Be sure you are using a good power supply. The Pi 3b+ needs a 5V 2.5A power supply. The Pi 4 requires a 5V 3A power supply. Buy one of the official Raspberry Pi power supplies if you're not sure.
Audio jacks (and headphone jack) mount from the bottom
NOTE - if you use the CUI MJ-3536 jacks from Mouser, you may need to trim or file the pins to fit in the pcb. The CUI jack pins are just a tiny bit wider than the PJ302M jacks.
These all attach from the bottom. Values are marked on the board.
NOTE - the caps have polarity. The long pin of the capacitor is the positive pin (+) (this is marked on the board as +). The negative pin (-) is marked on the capacitor as a stripe down the side.
The 2x20 (for the pi) goes in from the bottom.
The 1x20 (for the display) goes in from the top.
Pin 1 is marked on the bottom of the switches. Pin 1 on the pcb is the lower right corner - there's a very small dot there.
Do these last. Don't worry about mounting nuts/washers
NOTE - Don't solder the display directly to the Fates pcb. Use the low profile header listed in the BOM. You won't want to desolder 20 pins to remove it if something goes wrong with the display.
I use the following method for the display pins - insert the long end of the header pins from the top of the display and then solder them in place from the bottom. Then clip the short header pins from the top.
This ends up with about 6mm between the main board and the display carrier board. You could trim the pins if you want the display to sit lower. My case designs include a 6mm standoff for this mounting technique.
You can attach the Pi and power it without an SD card inside and then test voltages on the board
