At the very least, it looks like the solder job on that diode has shorted the two terminals. See that big blob of solder at the top touching the ring underneath it? That’s the same ring the tab at the other end of the diode is connecting to. I would strongly recommend using some solder wick to clean up the connections, ensure you haven’t bridged anything that’s not supposed to be, and starting over. You also don’t have enough solder on the top leg of that diode for a good mechanical connection. A little vibration would weaken that enough for it to just pop loose again. The solder should envelop the lead pretty fully, not just create a small spot connection under the lead to the tab you’re trying to connect to. At the same time, you don’t want big blobs of solder hanging around where none is needed, which certainly looks like what’s shorting the connection between the red wire and the ring underneath it. Same story in the next picture down- there’s a wire there with no mechanical connection to the tab you’re soldering it to, just what looks like a way-too-big blob of solder forming a weak mechanical connection to the underside of the wire.

In the absence of a picture, if you have (or can download) a schematic of the game, you should be able to trace where the leads are supposed to go.

That 7805 is a voltage regulator and looks like it has burned all to hell and back. Check the voltage (ground on middle pin, input voltage on pin 1 (left) and output should be 5V on pin 3(right.)). Start there, if it’s not providing the right output voltage under load nothing else will work right.

If I was going to guess, I’d say that at some point the board took excessive incoming voltage from the upstream power supply and toasted the components in the line of Fire. You may not need to shotgun everything, but start with the regulator, and possibly the obviously overheated resistors and/or caps that share that power rail. If it still doesn’t look better after that, work your way downstream from the regulator as those transistors and diodes it powers may not have liked it either.

In any event, check the input and output voltage on the regulator first to verify the theory that it’s toast.

One more thing: looks like the output of the 7805 is not going to be 5V but rather 8.8 according to the schematic, because the common pin (middle) seems to biased up from the usual 0V by the 10K resistor and the 3.9V Zener diode, R9 and Z1. Kinda makes you wonder why they didn’t just use a different regulator...

You can’t feed a 7812 with 12V. The old linear regulators have a minimum drop from in to out of at least a couple volts. But yes, buying in bulk and reusing parts from elsewhere in the BOM saves a bunch of money, as it usually does.

That regulator may be questionable, but we should recheck against a real ground: Because the middle pin is not actually at ground, move the black lead to a solid ground and see if you get closer to 12 at the yellow arrow, and around 3.9 at the middle pin if the resistor and the zener are OK. If the yellow pin is nowhere near 12, then there’s an input voltage problem. If you move the black lead to a real ground point, the red arrow should read within 10% of 8.8V. If any of those voltages are more than about 10% off, consider changing the regulator, and also the Zener and the resistor if the middle pin voltage is not near to 3.9V.

I’d change the regulator and the Zener. (Zener polarity is important- get the stripe at the correct end if you replace it.). Measure the resistor across its leads in ohms mode and it should be 10K(ish). If not, replace that too. Voltage is definitely too high at the regulator output.

Might as well get a clean screw to hold the new regulator to the heatsink, and put a little thermal grease between the underside of the 7805 and the heatsink so it conducts heat well. Easiest way to desolder the reg will be to clip the leads, take the part off, then unsolder and pull the remnants of the legs one at a time.