Troubleshooting the Universal Ultra

[uniman]

Now that I have some experience working on the Ultra Series, I'm seeing a common weakness.
It is the MPU where it plugs into the motherboard. (or backplane board as some call it)
Most often this problem arises after a machine is moved or the MPU board was removed and reinserted.
The symptoms are all kinds of problems. No LED's, won't accept coins, error 31 - overpay, reel errors, etc.

The solution is;
With the machine turned off,
Remove and inspect the MPU board pins for discoloration or corrosion. Use a magnifying glass! Even small corrosion will cause problems.
I use a soft brass brush to gently clean the corrosion off the pins. Then make sure no brass strands are left behind. Again, I use the magnifying glass to look for stray brass strand fibers. They can short the board!!
I then liberally spray the motherboard pin connectors with contact cleaner. Put a small towel under it to catch the excess. Then spray the pins on the MPU and insert it in/out a couple of times in the motherboard. Give some time for the contact cleaner to evaporate and then wipe off any residue that ran down the motherboard.
Insert the MPU and after it seats, I use my thumbs pressing on the white pull tabs and press firmly, left, right, and then both together. This assures a tight fit.
Perform a RAM clear while powering up (see Ultra RAM clear thread for this procedure) and it should work fine.

Here are some pics of corrosion on the MPU pins. I got this board some time back and someone had taped on a piece of paper saying the "3rd reel wouldn't stop, bad board." When I tested it the second reel wouldn't stop. Gave it a good cleaning and it now works fine!

[uniman]

There is one more step you can take to keep that Ultra Series slot from flaking out on you.
See the pic below.
Most machines for home use have the MPU door lock removed. You need to get a barrel type lock, 3/4" long or less is best, with the locking tab.
Then you glue or doubleback tape two pieces of wood or plastic on the MPU door. The idea is when the door is closed and locked, the wood/plastic is pressing firmly on the MPU corners keeping it connected to the motherboard.
Works great on those occasional stubburn boards.
My friend Clyde gets credit for this idea. 

[stayouttadabunker]

That's an awesome picture of the corroded pins Uniman!