Repair of diver board Gottlieb system 1.
My thanks to B. Thompson ( U.S.A.) who proof-readed these pages.
All Gottlieb machines of the system 1 group use this board. The bad thing about this board is that it doesn't offer much protection in cases of shorts in the coil section. Meaning hat when a coil burns out, the driver transistor AND the driver on the CPUboard will probably burn too. Combine this with the fact that the main IC's on that CPU board are completely obsolete and it's easy to understand why system 1 pinball machines are not loved by repairmen. In many cases the CPU board is lost. There is a drastic solution which involves replacing the CPU board. There are already two types of replacement boards for the irreparable CPU board. They are the Ni-wumph board made in the USA and the PI-1 board of P.Janin of France. When using one of these, both excellent replacement boards, you must be sure the power board is ok, ( measure the tensions) and that the driver board is in good shape, otherwise you risk blowing up your new installed CPU board!
This repair method will therefore test all IC's and ALL the driver transistors on the board, this while the board is on the bench out of the machine. You do not need much material to do this. You need two push-buttons, one switch, and some cheap edge connectors. For those who will repair these driver boards on a more regular bases it is the possible to make an automatic switch. Both mountings will be covered in this article.
The first thing we need to connect the board on the bench are the Gottlieb edge connectors. These are expensive or difficult to find. The solution is to use edge connectors as used in JAMMA style Arcade video games. The JAMMA connectors are very common and still cheap. These edge connectors are double sided but we use only one side. You can cut them at the size you need or glue them together! ( see photo's) It is possible, but not recommended, to skip the connectors. You can solder the connections needed to perform the test directly on the edge connector strips of the board. Afterwards you warm up the solder and wipe it away with a cloth or sponge.
Jamma edge connectors( the step is 3.96)
This connector had one pin short , I glued a plastic strip on both sides to hold the added piece with one extra pin.
Here 4 pieces where cut and added together forming one whole connector covering J2,J3,J4 and J5 of the board..
The test-connectors on the board.
On top J1, and at the underside the one composed long connector covering J2,J3,J4 and J5.
What is the meaning of the test mounting? Well we are going to steer all the output driver transistors, those in command of the coils and those in command of the lamps of the pinball machine. Most of these drivers are activated by IC's ( flip/flops), some are directly steered by the CPU board. For the directly steered ones we will apply a small current on their base. It will be the flip/flops that we will place in an "on" or "off" state, the connected transistors have to follow these commands. In all cases we will monitor the outputs using a test-led, again this test-led will give us an "on" or "off" if all is well. To steer the flip/flops we need a "clock-pulse"that will be a simple push-button, furthermore the flip/flop needs a positive or negative tension on its inputs. Depending on the tension present at the inputs the clock pulse will toggle the flip/flop in its "on" or "off state. I have two methods of generating this, a simple mounting using a toggle switch, or an automatic switch. Here you make the choice if you will use the method on several boards or very occasional. Let's start.
Print the schematic .....
How are the connections on the connectors we put on the board? See the drawing here;
The large composed connector covering J2,J3,J4 and J5. The here following pins are ALL connected together: J2 pins 5,6 and 7, J3 pins 10,19,and 21, J4 pins 1,7and 8, J5 pin 16.
At the upper connector J1 we have three groups,
GROUP 1: interconnect pins, 1,2,3, and 4.
GROUP 2: interconnect pins 5,6,7,10,13,14,15,16, and 17.
GROUP 3: interconnect pin 8,9,11,12,18,19,20, and 21.
On pin 22 comes O volt and on pin 23 +5 volts.
GROUP 1 is connected to a toggle switch ( simple mounting)( and toggles between +5 and 0 volt ) or to the automatic switch.
GROUP 2 is connected to a push-button , the other side of the push-button is connected to 0 volts.
GROUP 3 is connected to a push-button, the other side of that push-button is via a resistor of 470 ohm connected to +5 volts ( simple mounting) or again via a 470 ohm resistor to the automatic switch.
At the underside the 4 connectors ( forming one long piece ) with the connection wires. Where J2 is the most right one ,and J5 the most left one.
On top J1. At the right side the red/black wire of the 5 volts ( black=0 red = +5)pins 22 and 23. The three other wires are the three GROUPS, left the brown wire = GROUP 1, the middle white wire GROUP 2, and right GROUP 3 with the purple wire.
Users manual for the simple mounting.
Using the simple mounting we have two push buttons and one toggle switch.
To test the transistors Q25,26,27,28,29,30,31, and 32 ( = direct coupling transistors) use the push button of GROUP 3. As long as you push, these transistors will conduct, and you can control the outputs using the test-led. The outputs are to find at pins 1,2,3,4 of J2, and pins 2,4,5 and 6 of J4. The test-led is connected between +5 volts and the output pin. If the led does not light up when you push, the transistor is bad.
Before using the test-led for the first time, try it by touching the 0 volt, the led has to light up.
To test the outputs of the drivers connected at the flip/flops, follow these guidelines;
Touch with the testled point the following output pins, J5 pins 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18, and 19. On J3 pins 1,2,3,4,5,6,7,8,9,11,12,13,14,15,16,17,18, and 20.
The led will be "on" immediately, if not, change the toggle switch and push pushbutton of GROUP 2. Every time you change the toggle switch and push the pushbutton of GROUP 2 , the test-led will change from "on " to "off"( all outputs will change at the same time from "on" to "off", you can control them all at the same time testing from one output pin to the next) If there is one that does not follow then the driver transistor is bad. If there are 4 of the same flip/flop ( Z1 to Z9) then the flip/flop IC is bad. All outputs must be tested to go in "on" AND "off" position. If there are outputs that are always "on" or always "off" the driver transistor is bad.
Using the automatic mounting.
Using the automatic mounting we only have one push-button.
GROUP 1 is connected at the automatic switch.
GROUP 2 is connected at the push-button , the other side of the push-button is connected at 0 volt.
GROUP 3 is connected thru a 470 ohm resistor at the automatic switch.
The automatic switch.
This is the material we need to make the automatic switch.
A small box to mount everything, one push-button, some wire, 2 plugs to connect at a 5 volt power source, one NE555 with socket, one electrolytic condensator of 4.7µF, one condensator of 20nF, a led, resistors of 470 ohm, 22K ohm, 6.8K ohm and a small trim potentiometer of 470K ohm.
Here the schematic of the automatic switch.
The test-led is incorporated in the same box as the automatic switch.
The finished automatic switch , red/black wires are the 5volt leads, the orange wire is the output. The whole print is 1x2 inch. The trim potentiometer is used to set the "ratio" of the pulse at 50%. Meaning that the positive and negative portion of the switch pulses will be about equal. To obtain that , place the test-led at the output of the switch , and turn the potentiometer, until the led is the same amount of time "off" and "on".
Everything put together. Upper left the wires to the 5 volts supply, emerging at the bottom of the box, the wires to the three GROUPS on J1, and the 5 vols to the board, on the right a curled wire coming from the test-led ending at a test-pin to touch the outputs. On the box the push-button, to set and reset the flip/flops, and at the left the control-led.
Thanks to the automatic switch the output pins of the direct driven transistors will blink all the time, if not the driver is bad.
The outputs of the transistors driven by the flip/flops will all be "on" or "off" at start-up, just push once or twice to change the status of the outputs , from "on" to "off" to "on" ( sometimes it is neccessary to push twice , the push has to come at the right moment when the input is just "high" or" low" depending of the previous status, as the switch changes every 1/2 second of position you have one change on two to push on the right moment, but mostly it is ok the first time..) If there is, among the 36 outputs, one ore more that does not follow , again the driver transistor is bad, if it are 4 outputs coming from the same flip/flop IC the IC is bad ( Z1 to Z9).
Which pins are the outputs at which connectors refer to the text of the simple mounting.
All outputs are to find on the composed connector covering J2,J3,J4 and J5. In the middle of the driver board we see 32 little transistors, these and the four larger left transistors are all driven by the flip/flops. In the middle there are 5 more transistors with the big 2N3055, and at the right again 4 transistors.
As the used connectors are double sided the pins at the component side are all free. I take advantage of these free pins to connect the outputs of the 32 small transistors at the 32first pins and then the 4 other transistors driven by the flip/flops, then the ' transistor outputs of the middle ones and at last the 4 most right transistor outputs. When testing, I slide with my test pin over all these pins ( at the component side) and can control very easily all the outputs. If one is missing, I know which transistor is bad. For example when pin 14 is missing it is the 14th small transistor which is bad and so on. Do not forget the 36 first ones are the transistors driven by the flip/flops and the last 8 ones the direct outputs.
One last important remark, The output of the big 2N3055 is at pin 2 of J4. ( for me pin 36 on my upper row of pins ) This is an exception as the 2N3055 is the only one that has an extra driver added ( Q29) When the output of the 2N3055 tests bad remove it and test again the output of the driver transistor just left of the 2N3055, on his left pin. If the output follows the rest of the outputs the driver is ok, if not the driver( Q29) is bad too.
Extra tip 2.
When you choose to use the automatic switch , add three female banana plugs at the box (a red , black, and a green one). Connect the red one at +5 volts the black at 0 volt and the green at the output of the switch. You can use the switch to repair the driver boards of Bally and Zaccaria. I will add the use of such a switch at the existing pages very soon. This is already announced in " Latest updates and changes." of the website.
Using the test box , and once you have connected the two edge connectors , it takes about one minute to control the whole driver board. At the same time you have a slow pulse generator , when you did choose for the automatic switch model,( mount the extra three banana-plugs ) , useful for different other repair methods, on pinball boards or other devices . I think it is worthwhile to have that at hand! Succes !