I know first, I would like to see a picture of the board. Do you have power and ground on the U16? Make sure you are testing on the legs of the part, especially if you have it in an IC socket.

The battery corrosion may eat into the trace and sever it right at the pin pad and may not even notice it, especially if you already lightly sanded the trace to expose the copper.

If the board had battery acid leak in the past and it wasn’t neutralized, I’d grab your ohmmeter and beep out the traces surrounding the corrosion you describe. I’d also remove the battery holder (if it still exists) and inspect the traces under it. I’ve repaired a few of them that failed years after the batteries were removed as the acid will continue to do damage if not properly treated. Good luck!

The diagram was a 'work in progress' and the first few versions in post #1 were unfinished/incomplete. In Januari 2017 I made the final corrections and all previous versions were deleted from post #1.

That is important to know.
The LM339 needs besides an INPUT, also a reference input (+5V) and power supply, (+12V and GND), check all those pins on U16

Hope these help. Remember LM339's have different connections for + and ground.

On an LM339, pin 3 is B+ and pin 12 is ground.

U16 (resized).png

U17 (resized).png

Need to be sure you remove all the black areas of the battery corrosion from the board, or it will still continue to spread like cancer and continue to eat up traces and parts. An example of one I had repaired.20170408_115512 (resized).jpg20170421_185553 (resized).jpg

You definitely have some more work to do. Pretty much can follow the corrosion from the bottom left and right battery pack holder holes and see the damage from there that spread up the traces and also and fumes that got to the resistor leads that are marked off. Picture does not have good light on it, so there could be some another area that I can't see affected. Could even use other pictures from other angles. Hard to really tell if L1 and C32 were affected. Some of the resistors I marked off on the right may not be damaged, just might be the way the light hit the area.

Basically, if the solder joint and solder leads are not shiny, need to suspect it for having battery corrosion. Magnifying glass is your friend for closer examination.
pasted_image (resized).png

I always replace the parts there were hit. I remove the damage parts, sand the affected areas down to the copper, treat the areas with vinegar, clean the board with alcohol, fix any damaged traces, reclean with alcohol, and repopulate with new parts and coat the bare copper areas.

My opinion, I can not see how the Zep is supposed to clean inside the parts that were affected. Sure it may look like it from the outside of the part, but you can't exactly scrub inside a part, much less under a part if the part is mounted tightly to the board.

https://pinside.com/pinball/forum/topic/terrybs-guide-to-repairing-alkaline-battery-damage

If you use the Zep instead, still make sure you are replacing the damaged parts. I definately would remove that IC16 socket just so I can get underneath and clean the board under it.