Investigation: x-review dhr.X-inspect returned samples.Analysis and findings: complaint #2020-07-0000211.Distribution history: this complaint unit was manufactured at csi on 6/9/2017 under wo #(b)(4) and shipped on 7/12/2017.Manufacturing record review: dhr's (b)(4) were reviewed and no non-conformities, related to the complaint condition, were noted.Incoming inspection review: not applicable.Service history record: no additional service history records found for this unit.Historical complaint review: a review of the 2-year complaint history showed no similar reported complaint conditions.Product receipt: the complaint unit was returned on a repair.Visual evaluation: visual examination of the complaint unit revealed no physical damage.Functional evaluation: complaint unit was functionally evaluated and found not to function properly.Root cause : the zener diode z1 protects z2 and functioned as designed.A check on the regulator providing the 5 volts (dc) to the display board was operating as expected and at 0.2amps.Once the z1 diode was removed, the board was powered up due to being in parallel with z2.The diode is activated at 5.3 to 5.8 volts and is not operating until it sees a voltage in this range.Once exposed to a voltage in this range it is operational.As the regulator has a steady output of 5 volts, this component is primarily not in use/activated.To burn out as it did, it would have to have been activated and would see at a minimum of 1 watt which is twice its rating.Alternatively, if damaged it may have been compromised to lend itself to be prematurely prone to burning out.No definitive root cause for this issue could not be reliably determined at this time.It is likely the diode was damaged or defective and the failure of z1 is considered confined to this component.Was the complaint confirmed? yes.Correction and/or corrective action: none.Reason: no further training required at this time.The unit was fitted with a new board, tested to specifications and returned to the customer.Coopersurgical will continue to monitor this complaint condition for trends.
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