The device history records for the sam 350p device and pad-pak were reviewed and this confirmed that all manufacturing and quality checks and test had been successfully completed.No rework was conducted.The sam 350p passed ¿out qat from heartsine technologies on the 7th december 2015.During the investigation transistor q45 was measured and found to have failed.This had resulted in the red status led illuminating incorrectly intermittently as per the reported fault.The fault was witnessed during the investigation.Additionally, this had resulted in the device failing to carry out the scheduled weekly auto self-tests.The gate of q45 is connected to the interrupt line from the rtc ic, u20, while the source of q45 is connected to ground.Leakage between these two pins had resulted in the interrupt line on the rtc ic being dragged low.This would account for the above faults.The faults could not be replicated when q45 was replaced.After replacing transistor q45, the device was temperature cycled between 0°c and 50°c for 48 hours while performing a self-test every 20 minutes.This is equivalent to approximately 33 months of normal use without fault.It is the policy of heartsine not to refurbish devices which have been returned from the field, after investigation, therefore this device shall be scrapped and replaced with another device of the same model.
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