6n137 failures- midi isssues

hi all.

hoping to gain some insight into a recent issue ive been experiancing on my ambika.
about a year or so ago i had and issue where the 6n137 opto had failed. i replaced it and it worked normal, now it has failed again but very quickly. my question is this: is there something else in the midi circuit/path that could cause this to happen (cap-diode etc) or possible a bad order of optos (fairchild manufactured_ BUT didnt have a registration - orientation dot/marking??) .

any help is appreciated.

thank you!

There are resistors and a diode on the input side of the optocoupler. You could check those.

hi all…

seems this issue is reoccurring. ive removed the MOBO with the 6n137 and associated parts, replaced both the diode and resistor… and it functioned fine for abut 45 minutes, then the same issue has happened again. this is my 3rd replacement of the opto. ive even ordered another set of optos thinking maybe i had a bum run of parts or something…but it seems its inherenet now… would there be anything in the incoming midi that would cause this to happen (changing midi patchbays???) or errant voltages in the midi packets etc??? im really missing having the ambika in use and any help is greatly appreciated! thanks all!