T3.5 'AN-W09' dual-diode package too hot to touch?

paynterf

Well-known member
The main controller in my robot - a Teensy 3.5 started acting up today, and now refuses to program at all, even with nothing connected. Doing my engineering 'smell and touch' test, I noticed the device marked 'AN W09', which from the schematic appears to be the dual diode package marked as 'D1' is a lot warmer than the same part on a 'known-good' T3.5. After 50+ years as a design engineer, I have a pretty well calibrated finger for temp measurements - I have noticed that when a device gets above about 60dec C I can no longer keep my finger on it. This device isn't quite that hot, but it's close. I also measured the temp at 49deg C with my Greenlee DM-4 with the supplied HUADA thermocouple.


Any thoughts? Is this T3.5 doomed to the trash can?

TIA,

Frank
 
Along the same lines, I note that replacement Teensy 3.5's are no longer available (chip shortage?) although Teensy 4.1's are. Is the 4.x line now mature enough to use in place of Teensy 3.5's? Any major drawback to replacing a 3.5 with a 4.1 - other than the fact that 4.1 pins are apparently not 5V tolerant?

TIA,

Frank
 
Thanks for the input. You are correct - I am not using that library. I'm actually using very few libraries, although I am using The 'FlashTxxx.h library for OTA updates - will that be an issue with the 4.1?
 
Thanks for the input. You are correct - I am not using that library. I'm actually using very few libraries, although I am using The 'FlashTxxx.h library for OTA updates - will that be an issue with the 4.1?

FlasherX works with Teensy LC, 3.x, 4.x, and Micromod.
 
D1 is reverse polarity protection on the DC input - if its hot its carrying significant current. If nothing is connected, it suggests one of the chips has been damaged or perhaps a shorted out component. A close visual inspection for metallic debris might be worthwhile.
 
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