swiftowl7 said:That’s about right—well, from a layman's perspective, anyway—though it might be more accurate to say something went wrong on the board itself.
External devices run on 5 volts just like the monitor does, and that specific circuit is... well, dead.
The good news is that if the main chip is still functional, it doesn't change much. Otherwise, you have a series of chips controlling the current flow, which takes the input voltage, splits or converts it, and then distributes it to maybe two or three different spots on the motherboard.
Since you already have the board out of the machine, you could try testing the voltage around the external unknown ports—though, honestly, it is EXTREMELY difficult for a non-expert to detect anything, let alone pinpoint a fault. That failure could be located anywhere on the path between the primary chip and the next chip responsible for distributing the voltage.
If the voltage at the unknown port is sitting at 0v (totally dead), in my opinion, a transistor or a diode has given up the ghost. Or, perhaps, if there was a short circuit, a micro-fuse might have popped right along with them. These components are so tiny they're almost invisible; for a layman, it's a nightmare trying to tell the difference between, say, a resistor and a fuse that look identical but have completely different readings.
There’s also the added risk that one single slip of the multimeter probe while the board is powered could cause even more damage without you even realizing it—so keep in mind that you could accidentally brick the entire board.
Are you actually hoping to repair the fault yourself? After seeing your questions, I’d call that nearly impossible. It would be much simpler—and far less risky—to just swap the board for a used one, though finding a good one is its own kind of headache.
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Repairing a motherboard is an INCREDIBLY expensive and complex undertaking. Even here in the States, where parts might be easier to find, it's such a massive hassle to do without a schematic that it’s really only worth it for high-end, high-value machines or when spare parts are absolutely impossible to find anywhere.
Morning! Thanks for the reply. I took a look, and there is 5v at the ports, but the connected devices won't power up. Also, there's 20v at the display connector, so the backlight should be working, but there's nothing? 😁 ....
I tried my colleague's suggestion to leave it overnight, but still, no image.
Just so you know, if I end up frying everything with the multimeter, it's not the end of the world. I'm just curious to see if we can figure out where the problem MIGHT be, because the local repair shop concluded the board is shot and that fixing it isn't worth the cost—which I already know, but hey, what do I have to lose?
Thanks again, and please let me know if anyone knows what the next step should be.