Here is what I saw with both this and the Parent's comment about LRU's, and this is in the context of the CVN's where I did my work. Every vendor uses something different ( count how many flat panel computer model's are on a CVN ) so instead of being able to swap the hard drives or PSU on a embedded PC you throw the whole thing out and replace it. Same goes for most control hardware. There may be dozens of independent control systems using pretty much every vendor of controller. I would love to see the IC's be able to rebuild any control system underway and re-program it, like they could do with the old analog based systems.
Oh, nobody would be repairing flat screen monitors (though I replaced CRTs while I was in), but get into radars and fire control systems and servos and such and those definitely get repaired onboard. When the choice is replace a 50 cent resistor or send the module off and wait six months for a spare that costs the ship half a million bucks, you better believe people get the job done.
I owned the 2M shop on a CVN for a while. We repaired millions of dollars worth of equipment.
