Hey all,
Just had an interesting Bally -17 MPU repair, thought I'd share in the off chance someone else comes across this problem.
Pin was having switch problems (certain switches registering fine, some switches registering as other switches in test mode but then registering as a different switch again in game play), so I looked for all the usual suspects: MPU connector, 5101, sockets, physical wiring... and no luck. The really strange part was that the switch problems were consistently incorrect. In some ways I like those problems better because an inconsistent problem is a real kick in the pants to track down. In this case, the consistent part was really frustrating.
So after chasing my tail with this current problem, I found this online http://techniek.flipperwinkel.nl/ballyss/rep/index3.htm#smatrix :
I tested and sure enough, some of the switches were not working at all. I replaced all 4 banks of dips, reflowed solder and tested all corresponding diodes, and sha-zam. Works perfectly.
Not a common problem I've had to deal with for Stern / Bally MPU, figured I'd share.
Daniel
Just had an interesting Bally -17 MPU repair, thought I'd share in the off chance someone else comes across this problem.
Pin was having switch problems (certain switches registering fine, some switches registering as other switches in test mode but then registering as a different switch again in game play), so I looked for all the usual suspects: MPU connector, 5101, sockets, physical wiring... and no luck. The really strange part was that the switch problems were consistently incorrect. In some ways I like those problems better because an inconsistent problem is a real kick in the pants to track down. In this case, the consistent part was really frustrating.
So after chasing my tail with this current problem, I found this online http://techniek.flipperwinkel.nl/ballyss/rep/index3.htm#smatrix :
MPU Board DIP Switch Problems.
There is another area where the switch matrix can go crazy. This is at the MPU board's 32 mini DIP switches. These switches too have diodes, but if one diode goes bad, the DIP switches can be mis-interpretted, and this can cause havoc in the switch matrix.
If you suspect the MPU board's DIP switches as a problem, just turn them all OFF. This essentially removes them from the switch matrix. Then the DIP switch's diodes can be individually tested using your DMM (set to the diode setting). With the game off, you should get a reading of .4 to .6 for each diode, and when the DMM leads are reversed, a zero or null reading.
I tested and sure enough, some of the switches were not working at all. I replaced all 4 banks of dips, reflowed solder and tested all corresponding diodes, and sha-zam. Works perfectly.
Not a common problem I've had to deal with for Stern / Bally MPU, figured I'd share.
Daniel
