Hermes F3, wrong part...
Posted: Tue Apr 11, 2017 8:59 pm
I received this email from someone who asked me to post it for them, as they are a bit shy about doing it themselves. I don't have an ANAN-10 and therefore can't report on any instability, however his findings are certainly very interesting--73, Scott
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Just a heads up. I finally tracked down a hardware instability in my ANAN-10 (TAPR Hermes board/APACHE 10W PA/Case). Symptom: random crash after prolonged period of operation. It seems that the Thermal re-settable "fuse" F3 on the Hermes board is the wrong value. The schematic shows a 2A "fuse". The BOM indicates a part# of MF-MSMF110/16-2CT-ND (indicated as a Bel Fuse part but actually Bourns). The measured current in F3 is ~1.6 amps. The part is spec-ed at Ihold=1.1A and Itrip=2.2A. The part is operating in its transition zone!
They seemed to have chosen it for its trip point and didn't look at its hold rating. My thermal camera shows it running at ~90C! Not good.
I replaced it with a 2A hold part and all is good.
This is just some info that you may want to keep in the back of your mind, if anyone is experiencing random issues with their ANAN-10.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Just a heads up. I finally tracked down a hardware instability in my ANAN-10 (TAPR Hermes board/APACHE 10W PA/Case). Symptom: random crash after prolonged period of operation. It seems that the Thermal re-settable "fuse" F3 on the Hermes board is the wrong value. The schematic shows a 2A "fuse". The BOM indicates a part# of MF-MSMF110/16-2CT-ND (indicated as a Bel Fuse part but actually Bourns). The measured current in F3 is ~1.6 amps. The part is spec-ed at Ihold=1.1A and Itrip=2.2A. The part is operating in its transition zone!
They seemed to have chosen it for its trip point and didn't look at its hold rating. My thermal camera shows it running at ~90C! Not good.
I replaced it with a 2A hold part and all is good.
This is just some info that you may want to keep in the back of your mind, if anyone is experiencing random issues with their ANAN-10.