Open the door, then open the mpu door. Press the three little buttons on the front right side of the board. (Two are bigger.) Press these three and hold them down while powering up the machine. Right next to those three buttons are four little red LED's. They should light up and then blink left to right after startup. If they don't light up you have a problem. I'm guessing they won't light up or maybe all are flashing at the same time.
Pull the board and check the battery area (back right). Look for corrosion on the board. Battery damage is common.
THE BIGGEST PROBLEM with the Ultra Series is the mpu board connection to the backplane!!! Get a little soft brass brush (Walmart) and electronic parts cleaner (Autozone).
Pull the board and spray all the pins. Use the soft brass brush to clean the pins. Make sure brush is soft, don't bend pins! Make sure no brass brisels are left behind on pins.
Then spray the backplane pin holes. Don't worry about overspray, it will evaporate. Hit it good! Then insert the board in and out of the backplane a few times while still wet with cleaner. Let everything dry and then insert the board. Press evenly on both sides on the board to get it seated. Now, when powering up you will need to push those three buttons, but put your thumb under the board so it doesn't flex down. Power it up and see if there is an improvement.