Leon Borre Bally & Stern Solenoid Driver Board Repair
Repairing your Bally - Stern- solenoid-boards.
This is an easy way to repair solenoid driver boards. It never results in burning coils and you don't have to work in an uncomfortable position..
Take the board out of the pinball machine. Instead of connecting coils we'll use simple leds in series with a resistance . This allows us to check all drivers at once and we don't need the dangerous 43 volt supply....
Schematics
in reality
The resistors are at the bottom side of the board. The little board is a universal test-board with parallel traces of each time 3 groups.
Use a series of leds next to each other. This way you are able to test several pins without the need to move the connector. The red wire goed to the 5 volt which can be found at test point 3 of the board.
Addition !!!
This test-board with leds will also be used to repair the lamp driver board. Therefore it's better to make one bigger model which can be used for BOTH tests. Another pinball freak (Aeneas) has had the idea to use different colored leds, so it is easy to see what leds have to light up on connector J1, J2 and J5. Some red leds are used by connector J5, the one green by J1, and the green and yellow by J2...
So before you start soldering, read both articles about the test boards, and then check the picture of the improved led board by Aeneas and his documentation about it which you can find here............ 
Connected it looks like this......
Driving the coils normally happes by a cpu or a test program. I'll draw a schematic of how this works......
..............................................this is replaced by 4 switches and a pushbutton......
The button is located at the side.
The 4 switches connect to:
J4 ; pin 6 to switch 1
J4 ; pin 5 to switch 2
J4 ; pin 4 to switch 4
J4 ; pin 3 to switch 8
J4 ; Pin 7 to button
The common wire goes to the mass.
Connected it looks like this......
All we need now is a supply of 5 volt. If you don't have one, a small universal dc-supply will do. Put a pre-wired connector (4 contact points are enough) to it and you're done!!
The 5 volt supply connects to J3........ 5 volt to pin 25
...............................mass or 0 volt to pins 24, 23 and 22
These transfos are for sale as universal models, with a switch at the bottom you can set the voltage between 4,5 en 12 volt. If you connect this, start at the lowest voltage. With everything connected, measure with a DMM how much volts you get. Maybe you will have to switch to a higher voltage to get the needed 5 volts out of it. Mine has to be at 7,5volt to actually deliver 5,4 volt.
Connected it looks like this.....
Usage:
Connect all 3 parts
The connector of the switchbox goes to J4. The common wire goes to the mass, this is available at a testpoint . On Bally boards this test point is marked GND, on Stern boards it's GND-TP8.
The connector of the power supply goes to J3. BE CAREFUL that you do not plug it in wrong !!
The series of leds must be connected to the pins you want to test. This can be J5, J2 or J1. The common wire should be connected to T.P. testpoint 3 = 5 volt. (As well on Bally as Stern.)
Operate the switches using the guide beneath to operate a certain driver or place on the connectors. Push the button to validate the connection and see if the led goes on..
With this test fixture it is possible to test 15 of the 19 coils..
I've tested and wrote everything down, here we go..
.....................................BALLY...or........STERN
1) Switch 1.... button=.... J5...Pin 8......Q16
2) Switch 2... button= ....J5...Pin 14...Q11
3) Switch 1 2 button= .....J5...Pin 13...Q12
4) Switch 4... button =... J5...Pin 15 ...Q10
5) Switch 1 4 button=... J5...Pin 9 .....Q9
6) Switch 2 4 button=.....J5...Pin 11.....Q14
7) Switch 1 2 4 button=.J5...Pin 12.....Q13
8) Switch 8 button =......J5...Pin 10.....Q8
9) Switch 1 8 button= ..J1...Pin 5......Q4
10) Switch 2 8 button =.J2...Pin 5.... Q3
11) Switch1 2 8 button=...J2...Pin 12.... Q7
12) Switch 4 8 button=.....J2...Pin 11.... Q6
13) Switch 1 4 8 button=...J2...Pin 10.... Q5
14) Switch 2 4 8 button=...J2...Pin 9 ..... Q1
15) Switch 1 2 4 8 button=J2..Pin 4 .... Q2
By keeping the button pressed you are able to select a solenoid (represented by a led), follow the path over the board, and so on up to chip 74LS154 and pr�-driver chips U1 U3 and U4 (CA3081) over the resistors to the real drivers SE9302 of BU649, and see where the problem is, if the led does not light.
With the solenoid board in the pinball machine you are also able to test, only remove connector J4 and connect the switchbox to it. With the switches and the button you are able to test all coils, even when the cpu-board does not work !
Good luck !!
Next; repairing "Lamp-drive-board" .............