Opened 3 years ago

Last modified 3 years ago

#10974 assigned defect

XO 1.75 - +3.3V_AUDIO is not driven

Reported by: wmb@… Owned by: wad
Priority: normal Milestone: 1.75-hardware
Component: hardware Version: 1.75-A3
Keywords: Cc:
Blocked By: Blocking:
Deployments affected: Action Needed: add to build
Verified: no

Description

The voltage on U24 pin 5 should be 3.3V but instead it varies between 0 and 2V depending on the mic bias voltage.

Inspection of both the schematic and the gerber reveals that the +3.3VA_AUDIO net is connected to several loads, but is not connected to any voltage source. Instead, it is getting its voltage from the mic bias supply via forward conduction of the top halves of D16 and D17.

One result is that the AC/DC switches U24 and U25 do not work correctly, thus preventing the use of the loopback cable for audio testing. Another result is mic signal distortion.

The audio subsystem works much better with a blue wire from that net to +3.3V_AVDD at C218. Perhaps +3.3V_AVDD and +3.3VA_AUDIO were supposed to be the same net?

Change History (2)

comment:1 Changed 3 years ago by wad

  • Action Needed changed from never set to add to build
  • Status changed from new to assigned

Confirming that +3.3V_AVDD and +3.3VA_AUDIO were supposed to be the same net.

To be fixed in B-phase.

comment:2 Changed 3 years ago by dsd

  • Milestone changed from Not Triaged to 1.75-hardware
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