I've been building USB powered audio DAC circuit which is using multiple LDO voltage regulators.

I discovered one of the regulators, namely TPS79333, which is responsible for supplying 3.3V to PCM2706 chip, is outputting 4.92V (more or less equal as input voltage). Is this a clear case of faulty voltage regulator or could a problem be something else? Is there a way to trace which component is causing it?

Also I'm afraid it's over for DAC chip with such high voltage on supply pins. :(

Thank you for your answers.

EDIT: To clarify I'm building PupDAC. Schematic can be found here: http://www.diyforums.org/PupDAC/schematic/pupDACschematic.pdf

Regulator in question is U2.

  • 4
    \$\begingroup\$ You say you've been building, but don't say you've been designing. And you ask now about how to find the problem. This suggests to me that you really are only building and not designing. Is that the case? If so, it will be vital that you disclose exactly what you are building and its full schematic, I think. \$\endgroup\$
    – jonk
    Jul 22, 2018 at 18:22
  • \$\begingroup\$ Why are you not using the internal 3.3 volt regulator on the PCM2706 chip? \$\endgroup\$
    – Andy aka
    Jul 22, 2018 at 18:34
  • 3
    \$\begingroup\$ outputting 4.92V .... are you sure that the voltage is not arriving to the output of the TPS79333 from another source? \$\endgroup\$
    – jsotola
    Jul 22, 2018 at 18:37
  • 1
    \$\begingroup\$ I will remove my vote to close if you add a schematic and picture. \$\endgroup\$
    – mkeith
    Jul 22, 2018 at 18:37
  • 1
    \$\begingroup\$ @PrimePriest Please write up your comment as an answer (and accept it) so that this question does not die officially unanswered. This would be a help to the community. \$\endgroup\$
    – mkeith
    Jul 23, 2018 at 22:21

1 Answer 1


Good news. Neither the regulator nor PCM chip are dead. Glad components nowadays are pretty tough. I put U4 in a place of U2 and it showed correct output 3.3V. I tested U2 regulator outside on a breadboard (it was painful to solder wire leads to SOT23-5) and frankly it worked perfectly fine. So I put it back in place of U4 and the board is working just fine. I still don't fully understand what was happening. Close visual inspection was the first thing I did and surely there were no visible shorts between the pins.Could it be some solder flowed under the chip and created short that way? Thanks everyone for your time>


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