@Spook50 Random thoughts...
Wild guess is that the first or most common failure one would see is cracked solder joints, particularly where the multipin connector is soldered to the board. Moisture would hurt too if it's a parts truck with broken windows dragged out of a field. Those electrolytic caps, like you suggest, also have a lifespan. But typically you see power filtering caps on big B+ rails having issues long before decoupling caps would - judging by the size, I bet a lot of those are for decoupling or else filter caps on a tiny B+ rail. The ceramics will last essentially forever. The carbon film resistors won't drift as much as older carbon comps will, so unless one of them is exceeding it's wattage rating those should last more than 40 years. Those look like 1/4w, and at worst case (14.7VDC) they can only handle 17mA. I would think most of what's happening in there is logic/switching network stuff that doesn't see significant current draw, but if they exceeded 17mA they could drift or even fail open. You'd probably see a toasty spot on the resistor if the latter was the case. The resistor point might be moot anyway, it looks like there's voltage regulators in there, possibly dropping the voltage to 5VDC for logic stuff, which means the resistors would be good to 50mA. Heck, I'd say a voltage regulator would go bad before the resistors. Out of all the gear I've repaired I've seen a few bad VRs, all about 30-40 years old. Not frequent though.
I bet a lot of those components are NLA or labeled with an in-house designation, obscuring what a replacement would be. It's too bad because you could just have new PCBs made and populate them with new components. That would maybe be more labor effective than refitting that board. Not that it couldn't be done redesigning the entire thing with modern production components. At the end of the day I agree with Godwin and other's assessment of how limited the market is. It would be a LOT of R&D (time + money) to sell a handful of them. You'd have to charge $$$$$ to recoup.
Not trying to piss in your cheerios, just sptiballing.
Wild guess is that the first or most common failure one would see is cracked solder joints, particularly where the multipin connector is soldered to the board. Moisture would hurt too if it's a parts truck with broken windows dragged out of a field. Those electrolytic caps, like you suggest, also have a lifespan. But typically you see power filtering caps on big B+ rails having issues long before decoupling caps would - judging by the size, I bet a lot of those are for decoupling or else filter caps on a tiny B+ rail. The ceramics will last essentially forever. The carbon film resistors won't drift as much as older carbon comps will, so unless one of them is exceeding it's wattage rating those should last more than 40 years. Those look like 1/4w, and at worst case (14.7VDC) they can only handle 17mA. I would think most of what's happening in there is logic/switching network stuff that doesn't see significant current draw, but if they exceeded 17mA they could drift or even fail open. You'd probably see a toasty spot on the resistor if the latter was the case. The resistor point might be moot anyway, it looks like there's voltage regulators in there, possibly dropping the voltage to 5VDC for logic stuff, which means the resistors would be good to 50mA. Heck, I'd say a voltage regulator would go bad before the resistors. Out of all the gear I've repaired I've seen a few bad VRs, all about 30-40 years old. Not frequent though.
I bet a lot of those components are NLA or labeled with an in-house designation, obscuring what a replacement would be. It's too bad because you could just have new PCBs made and populate them with new components. That would maybe be more labor effective than refitting that board. Not that it couldn't be done redesigning the entire thing with modern production components. At the end of the day I agree with Godwin and other's assessment of how limited the market is. It would be a LOT of R&D (time + money) to sell a handful of them. You'd have to charge $$$$$ to recoup.
Not trying to piss in your cheerios, just sptiballing.
