buildpcm5102a
you can follow the values indicated on the pcb. no special precautions required ###except:
- ignore/don't solder the resistor labelled "500R"**, right below to the raspberry GPIO header. that's for testing purposes only / it connects to the raspberry 3v3 supply. (see picture below)
in addition:
- better to use 33k resistors where the four 'mini-melf' pads are (the larger pads near the bottom right side of the board); the diodes would be fine, too. but 33k is what the BOM says.
- yellow: 33k, blue: 100n (not labelled on pcb). also note the two pin header / jumper labelled
5v_pwr. this connects the raspi to 5V. so, typically, you want to connect it; don't connect it, if you want to supply the raspberry externally via usb.
- when soldering the SOIC parts, watch out for the LM358. 'FERR' is for FERRITE. replace these with 10R resistors, if you don't have any. 0.1 = 100n, 0.33 = 300n.
- the DAC, ADC, and (if you like) fancy op amp goes here -- the remaining ones are TL072 and LM358 respectively:
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you can/should solder the electrolytic caps onto the bottom side, as pictured above.
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soldering the 2x20 sockets. note the holes are fairly small, as there's traces routed in between them. most suitable sockets should fit easily though (the one in the BOM does). when using model b+, make sure you leave enough head room for the dual usb/ethernet sockets.
- if planning to use (only) the model A+, the socket obviously can be less tall:
- view from the back, with model b+ mounted (NB: you don't want to use a usb wifi dongle, or, indeed, any usb device, in normal operation. it'll incur unpretty fluctuations in current draw):
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- if you have a first batch pcb (unlikely at this point), don’t solder the one 49k9 resistor in the vicinity of the top-most TL072 (as shown in the pic) - NB: this is no longer an issue with more recent versions of the pcb. (you can identify the version by spotting a/the resistor labelled "10k"* in the vicinity of the ADC, right next to the BAT54s diodes. if it's there, don't worry about 49k9 resistor)
old boards:
