Comment by themaninthedark

I would assume that you don't have access to the lab(and diagnostic equipment) at all times and taking other classes.

Also him being a student, having the wrong component was probably not in his mental troubleshooting tree. I would guess that it was not in the lab assistant's troubleshooting tree either.

Also once you start down the road of troubleshooting, a false trail can lead you far into the woods.