Bally Corvette Repair 2/19

Corvette service call 

I get a call from a new customer a few days ago, he got my number from a friend of his, referrals are always awesome. So he picked up a really nice Corvette, worked great at the guys house but when he got it home and set up it started randomly resetting after three games. 

Usually on the WPC game’s when that happens the bridges, BR1 and BR2 under the heatsink, need to be replaced. One tell tale way to tell if the bridges are failing is to start a game and hit both flippers continuously. If the game reboots then the bridges most likely need to be replaced. When you are buying new bridges get ones with long leads so you can mount them higher off the board. This will allow for more airflow underneath of them and extend their life. It’s also important to clean the old thermal compound off the heat sink and apply fresh thermal compound. It rarely happens to be the regulator itself. Another area of concern is the power input connector J101 on the driver board. The two upper red wire pins, pins 1 & 2, typically burn which will require replacement of the connector and housing. If it’s been burning long enough the header pins on the board should be replaced too.

So I pulled the driver board out and found that both bridges had been previously replaced, but the old thermal compound wasn’t cleaned off and new thermal compound wasn’t applied. Also they were short leads and the bridges didn’t have much breathing room. Pins 1 & 2 of J101 were slightly browned so I installed a new connector with trifurcon pins. The header pins on the board were OK so they didn’t need changing. I reheated the rest of the pins on the board and reinstalled it back into the game.

The logic board still had AA batteries in it which fortunately hadn’t leaked yet. I installed a new CR2032 battery board and battery and reinstalled the logic board back into the game after reheating it. 

Before final testing of everything I gave the playfield a quick cleaning even though it was already in excellent condition and replaced a few burned out bulbs. Upon initial gameplay everything was great, for a few minutes anyway. The game reset a few times but it was acting like the slam tilt was being activated instead of a random reset. Also it was only happening when a certain switch was being hit. The million switch was causing the slam tilt to activate. 

This is a good time to note that the switches are in an 8 x 8 matrix consisting of columns and rows. When one switch gets stuck closed, phantom switch readings can happen. This is where your switch edges or switch levels test are extremely useful. It was quickly determined that the skid pad stand up switch was always touching, no the switch leaves themselves, but the solder tabs underneath were touching. After that was fixed the game was re-tested and all errors were cleared. The game works great and his kids were up late into the night playing Corvette!

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