Testing of all drivers-circuits on a Williams-driver board, outside the pinball machine.

Lamp-strobe, Lamp-row, Switch-matrix-drive, Solenoid-drive, 6 Special solenoids

What you need:

The cpu board, driver board, and special test-eprom which you can down-load on this website (check the article about repairing cpu-board Williams) and as tester a led in series with a resistor of 10ohm. Also a testlight as described in my technical tips and tricks article.


Beneath the black shrink tube at the led there's a resisntor of 10 ohm.


In the manual I talk about the positive side of the testled and the negative side. To find it, connect both sides to 5 volt and mass. The positive side is the side to the 5 volts and the negative side is attached to mass, and this when the testled lights up!


Make a setup of the cpu board and the driver board on the same was as you would for reparing the cpu board (check other article)......

IC17 on the cpu is the special test eprom, which will generate a rythmic output on all outputs of PIA's which on their turn operate all driver circuits. We're going to check on the connectors to see if we have the pulses there too.

The outputs are these connectors:

1) Connector 2J2 = Switch-matrix-driver, all pins.

Here you connect the negative side of the testled and it should light in rythm. (The positive side is connected to +5 volt.) Is it doesn't light, trace the signal back via IC17 or IC18 to the PIA output. To trace the signal back, use the testlight as described in the tech tips article.

2) Connector 2J5 = Lamp strobe , all pins.

First connect 5 volt on any pin of connector 2J4, then check every pin of connector 2J5 with the testled (the negative side of the testled is connected to ground). If one or more pins don't work, use the test-light to check if there's a blinking signal on the entries of the IC which is present in the circuit, it'll be IC 13 or IC14. If there's a signal then first replace the output transistor (TIP42) and eventually the driver (2N6427). It isn't possible to trace the signal using the simpel test-light from the output of the IC, as the test-light isn't fast enough to visualize the very short signal.

2J7 = Lamp row , all pins.

First connect 5 volt at connector 2J4 any pin, then ground at connector 2J6 any pin. With the negative side of the test-led you check all pins of connector 2J7, if there's one which does not light then again trace with the test-light back to the PIA output. Here the signal passes over 2 transistors and a IC gate. Using the schematics and the test-light it's easy to check what component blocks the signal, replace that one. (here you can trace the signal with the test-light because the block-signal of the PIA isn't mixed with "blanking" and therefor it's a larger signal....).

4) Connectors 2J9 and 2J11 = Solenoid drive , all pins .

With the negative side of the test-led you can check all pins. If any doesn't blink, first replace exit transistor TIP20, and eventually driver 2N4401.

Connector 2J12 = 6 special solenoid drivers.

These drivers aren't controlled by the PIA's, to test them we use this method:

On connector 2J10 any pin, attach ground.

First output 2J12 pin 3 : negative side of the test-led; and on connector 2J13 pin 2 attach ground. This is the controlling signal, every time you touch this pin (2J13 pin 2) the testled will light.

Second output 2J12 pin 4 : negative side of the testled; on connector 2J13 pin 3 attach ground as control signal: touch this pin and the testled should light.

Third output 2J12 pin 6 : negative side of testled ; on connector 2J13 pin 4 connect to ground, again touch this pin and testled should light.

Forth output 2J12 pin 7: negative side of testled; on connector 2J13 pin 5 ground, same thing..

Fifth output 2J12 pin 8: same thing with connector 2J13 pin 8 to ground.

Sixth output 2J12 pin 9: same thing with connector 2J13 pin 9 to ground.

For the cases this doesn't work, trace with the teslight the control signal back over the 2 transistors and 1 IC, whilst the testled stayes connected!!. Replace the transistor or IC on witch the signal enters but don't come out.....



Be shure on the CPU board capacitors C31 and C32 where replaced. They are the ones that assure the timing and output of the BLANKING signal ,so imortant for the correct working of the driver board . Please replace these capacitors ALWAYS.

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