Thread: PCM
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Unread 16-03-2015, 10:14
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FRC #0365 (The Miracle Workerz); FRC#1495 (AGR); FRC#4342 (Demon)
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Re: PCM

On Team 365, we have a PCM that was dead on arrival (DOA). Team 4342 was generous enough to loan us their PCM while 365 goes through the RMA process.

Skipping to the cause of the failure, there is a solder joint fracture on one of the surface mount chips. This failure is unlikely to happen to any team with a currently working PCM (ours was DOA) so I will just briefly describe some of the symptoms:
First, this was a failure on the solenoid channels, compressor circuit worked fine.
Solenoids never switched on any of the channels. Webdash recorded a solenoid voltage of 3V, voltmeter could never pickup any voltage from the channels.
Initially, the channel LEDs would sometimes flash on momentarily (before a fault was indicated) and displayed some weird behavior (glowing faintly while off). Later in testing they were always off (I suspect the vibrations of the compressor made the solder joint connection go from intermittent fully off).
Frequent Solenoid Fuse faults reported on the webdash (both sticky and now). Status light was usually blinking red once. Faults were so persistent, they were difficult to clear (got some ironic Self Test messages indicating Faults with a message at the end that says "all faults cleared"). Occasionally, I could get the faults cleared and status lights normal. Once I turned on a channel (with nothing connected) the fault would return.
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Electrical & Programming Mentor ---Team #365 "The Miracle Workerz"
Programming Mentor ---Team #4342 "Demon Robotics"
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