Leon Borre Atari Driver Board Repair

Repair I/O board Atari

When the I/O board is connected to the cpu board by the normal inter-connecting cable, ( J4 on cpu J14 on I/O ) everything is connected at the same time, because the 5, 12 and ground are also included in this connection. That is the first easy thing about the I/O test. The second easy thing is that ALL outputs can be verifyed directly on the output connectors. These output connectors are; J15, J16, J17, J18 for the lamp drivers and J19 for the solenoids outputs.So put the test eprom in the cpu and launch the normal test with the I/O connected..

Alle the signals will give output as long as the cpu leds light up and go "out" again when the cpu lamps are out. The only thing to do is to connect a series of leds to the outputs and we can directly see wich ones are good and wich ones are bad. Bad means the connected led that stays "on" or a led that will not turn " on" at all.

Here you see the I/O board connected to the cpu board. On the J19 output i connected a series of leds to monitor the outputs. This serie of leds are the same as I use for the test on the driver board of a good old Bally. I will repeat here how it is made.

This is the schematic

This type of connector strip is soldered at the underside of the little board

Here you can see the connector strip soldered at the back side

On the front side I soldered the other type of connector ( using short leads) this connector type fits into the bigger solenoid connector at the I/O board.( J19) This way the test-led- strip can be used on both connector types.The bigger connector is soldered at pin 1, pin3, pin 5 and so on ( impair numbers) and also the impair numbers are red leds the pair numbers are yellow/green leds . All this is helpfull when to count and see leter on wich pin of the connector gives us a led that "stays on" or is missing...

Here you see the I/O board with the control leds in place at connector J18. It is connected directly with the connector strip at the underside of the "led strip board" and the 'big' connector for the solenoids is "floating" in the air...

User guide.

Interconnect the cpu and I/O boards by placing the connector J4 (cpu) and J14 (i/o) Place the test eprom on the cpu board and start up . The " common" lead from the" test-led-strip " is connected at 12 volts.

By placing the test-led-strip on connectors J15, J16, J17, J18 and J19 ,you will find the leds blinking in rhytm with the leds on the cpu board, this is the rule...but... there are some exceptions, and there are some non connected pins at every one of these connectors. So here comes the list of connectors and there " live" pins..!!

J15 ; pin 1,2,3,4,5,6,7,8,11,13,14,15,16,17,18,20 = live.... 9,10 12,and 19 nothing.

J16 ; pin 1,2,3,4,5,6,7,10 = live ... 8,9,12 and 19 nothing. SPECIAL = pin 11,13,14,15,16,17,18 and 20 these pins will go "on" and stay "on"...push reset on the cpu to see them go "out" again ...here the test is " a one time blink "(due to programming )

J17 and J18 ; pin 1,3,4,5,6,7,8,9,11,13,14,15,16,17,18,20 =live .... 2,10,12and 19 nothing.

J19 pin 1,2,3,4,5,6,7,8,9,10,11,and 12,14 = live (12 and 14 if the jumpers left to the J19 connector are present on your I/O board.) pins 15,16,17,18,19,20 = live

If ALL the outputs of the solenoids are missing ,than the fault will mostly be in the " inhibit" circuit. Measure pin 23 at B2 this pin must read 0 volt, any other value is wrong...To perform the solenoid output test follow these instructions.

At the component side look at coordinates A/B 3/4 you will see two jumper like runs next to eachother. Cut the left one , later on we will put a "real" jumper in place. Once cutted solder a lead at the under part of the jumper and connect it to ground. This will 'validate' the outputs of chip B2 that drives the solenoid driver transistors. See this on the photo below...

See the red jumper... Normally it is a "run" For test purposes the run was cut and replaced by this jumper ( as explained in text).

Now we are ready to chech outputs at J19.

When the pin 23 at B2 was not good ( must be 0 volt during test) that means the "inhibit" circuit is somewhere faulty... The circuit consists of Transistors Q106, Q65, Q66, Q81 and chip B4/5 . Measures the transistors to see if they are ok, if the transistors are ok replace B4/5 ( CD4013) .

Whenever a lamp stays "on" or will not light up you can follow the signal that must arrive to the led , with the schematic and a logic probe. Very easy because you can compare "good" and "bad" outputs....

When a hole lot of lamps will not light up , look at the schematic if they come all from the same driver chip. Could be that one that is broken. Lamp drivers are, C6/7,C2/3, C4, C5/6, D2/3, D4, D5/6, D6/7, If it is only one or two lamps , in general it is the driver transitor that will be bad.

Same thing for the solenoid drivers there are only two of these... B2 and A6/7. If here one or two solenoids outputs do not light up, it can be the predriver or the driver , look where the signals comes in and not comes out...

This is the complete the test for the I/O board .

Remarque;

With the completion of testing of both boards CPU and I/O the " INPUTS" are never tested this is not included in the test program. So it is always possible some switches will not work ..or some presettings of the switches on the cpu board are not ok... But as a good basic rule whe can say that the pinball will start up and you can use now the tests present on the pinball to check the rest of you circuitery.. Good luck with it, and I hope this tests will make it more easy to repair these Atari's and will take away their " difficult repair" reputation ..