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You can also add spacers (like these ones).

Avoid

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short-circuits with DIO FMC card

Another mechanical tolerances issue was encounter regarding the DIO FMC card, leading to a short-circuit. The symptom of this problem was that a LED from the front panel that was more intense than the second one, and its color turn into yellow instead of green. This LED was always shining even when it was not expected.

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An insulating rubber tape was also added on the two FMC cards to prevent an other short circuit to occuravoid short-circuitd.