Power Topology

Note that on my (non-functioning) PLAY:5, the connection (drawn as dotted line) between pin 6 of L27721 and the pair of EH31 VRs was not present. The EH31 VRs (U27704 and U27703) and pins 14 and 16 on the mainboard connector were not powered. Because the max input voltage of the EH31 is 20V, I reasoned that there needed to be a connection to the 12V output of the (main, high voltage) switching power supply. So I added this dotted line as a jumper wire on my PLAY:5 Main Board. I would be curious to know if, in a functioning PLAY:5, this connection in fact exists. With the jumper in place, all of the power rails now come up to the correct voltages (as far as I can tell).

The HT7225 2.5V LDO (U7705) seemed to be non-functional on my board. It appeared as basically a short from input to output, so the output was 3.3V, rather than 2.5V. 3.3V is below the "Absolute Maximum Rating" of the CS44800, so I expect the DAC should not be damaged. But this part needed replacement, as 2.5V is the correct voltage.

Missing refdes in diagram:
load switch for 3.3V to CPU - Q25005, Toshiba TPC6004
11.1V EH31 - U27704
5V EH31 - U27703


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