Ok, I installed the entire corrosion rebuild kit for the MPU as well as the Solonoid Driver/Voltage Regulator upgrade kit. That didn't get the cannon back up. I also resocketed and replaced the cmos ram P5101L-3 at U8, and that did. So, the game is up and running.
However now the problem has scurried off to find some other place to reside now.
I also replaced the manual reset button itself to no avail. For some reason I still can't reset without powering off or grounding pin 39 of the CPU. I am able to occasionally play a full game in it's entirety. What has taken hold now is a reset upon firing a ball on random occasions. I haven't found a pattern to it except that it only happens during game play, and when a ball hits a target.
The funny thing is when it resets, the blinking stops at like 4 flashes and resets again. Other times it will reset and come back up.
It may be the action of the cannon shot, or a bad PIA socket (since I also replaced the CPU and both PIA's) I'm really not sure. I think now my next step would be to replace the socketed PIA's and CPU at U9, U10, U11 as well as the 6810 ram IC at U7.
With any luck that may get it. Crossing fingers.
There is one other issue, that's not critical, but the bulb at L98 is always out on the playfield. I've replaced it, but it stays out. Basically, the invaders progress down towards their 'ships'. If all 4 invaders board the ship on the right, the bottom right lamp stays off-will not light. I'm not sure how, with two lamp driver boards, you find the correct transistor/ic that has the problem. Possibly something simple, but I've never touched a lamp driver board before.
As for the circular ball loader, it's acting a little aged as with play it seems to loosen up a bit and perform ok. I'm not sure what kind of maintenance should be done with that contraption. It seems to turn very anologue(ish) and not all the time moves with fluidity. It doesn't appear to be powered by a motor, more with the force of gravity and balls putting pressure on it to turn clockwise.
So, yea - spread spectrum, there's a few areas that I need to work on. If anyone has any ideas on any one of these areas, I'd appreciate your input.