DOM MB Diagnosis page

Board ID:

V5 000703

Source:

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Symptoms:                            

Failure during HASS.  No longer boots up.

Analyst(s):

G. Przybylski

Analysis Procedure(s):

September 7: Measured 3.3V low.  1.8V and 2.5V OK.  Lifted output beads.  Still bad. Replaced U8, the MAX1702B. Outputs OK. Restored beads. All voltages now OK.  
Loaded CPLD, the EPC8, and Flash memory. 
This board passes all room temperature STF tests.  The LED supply output voltages are correct.
Board bounced because the 3.3V ferrite bead wasn't reslodered after U8 was replaced.
November 8: This is really a non-problem. When beads were lifted for diagnosis during the previous diagnosis, it was not restored during repair.
For confidence, run exhaustive periodic (~2 min) reboot cycle while temperature cycling.  ~2000 reboots while cycling between -55°C and +65°C periodically over the weekend.  No boot failures observed.

Root cause:

September 7: Faulty switching converter controller U8. (overheated during reflow?)
November 8: Oversight during completion of repair

Mitigation:

September 7: Replace faulty part.
November 8: Resolder loose part;

Disposition:

Mainstream OK

Any Other Information:

Traveler
Traveler September 27
Traveler November 8