Quoted from cottonm4:I'm putting on my Joe Shadetree hat and go out on a limb here. I have/had a similar problem on my Nine Ball. I believe it is a diode problem. I replaced all my diodes ( I thought) but I still had the problem of isolating which one so I folded the pin up and will deal with it when I get my new Mirco NB play field.
( I had a diode go bad on my Big Game. Fortunately, I was able to isolate the sound for which switch was having problems and was able to fix the problem ).
I also have a friend with a NB and he has the same problem. I have tried cutting one wire to each switch one-a- a- time and that does not work very well. So, here is what I am going to do to try and isolate the problem.
This is the switch matrix for Nine Ball. You have 5 wires that you need to get familiar with. They are white/red, Brown/white, white/blue, white/yellow and yellow/red. They are hi lighted in the green. Study this little bit. Let's look at the brown/white wire: The b/w wire powers the switches to both sling shots, all three pops, the switches for Cancer and Gemini, and the center spinner.
These 5 switch wires control all of your switches.
[quoted image]
The one item that is not shown on this switch matrix is how the switches on the 8-place drop target are wired, but those switches have diodes, as well.
--------------------------------------------------------------------------------------------------------------------------------
This is the connector where those 5 switch wires live. You can see the white/red on the left. The others are here, too.
[quoted image]
That connector lives on the upper right corner of the MPU. The blueprint location is A4-J2-MPU. J2 will be marked on your MPU. It is also marked as to how many connector pins are in the connector, it tells you which pin is #1 and there is an arrow that points to which pin gets the block out key.
[quoted image]
=========================================
What I am going to do when I get another chance at my friend's NB is this.
1) Remove the play field apron. All 3 balls have to loaded in the outhole chute for the game to fire up. It takes a magnet stick to remove them before you lift the play field, should you need to.
2) Put the back glass in a safe place.
3) Remove that connector on the MPU.
4) By using a very small screw driver, I am going to remove the red/white wire from the connector. And I will reconnect the connector to the MPU and fire up a game.
With the game fired up, hit the credit button and start a game. If the offending sound remains then you know the white/red circuit is not the offending circuit.
5) Turn the game off.
6) Replace the white/red wire in the connector.
7) Remove the next wire. The brown/white wire.
8 ) Repeat step #4 only now with the brown/white wire removed from the connector.
9) Keep repeating this procedure with each of those 5 wires. Once you fire up and credit a game and the offending sound is gone, you will now know which circuit you need to look at.
10) Let's say when the white/yellow wire is pulled from the connector the offending sound goes away.
On the white/yellow circuit there are the Aquarius Stand up target, the Capricorn stand up target, the right (R) drop target assembly and the (cntr) drop target assembly.
11) Do the drop targets first. Cut or desolder the w/y wire from the right drop assembly. ( Make sure you use a jumper wire to continue the voltage to the to other switches on the circuit. ). By cutting the w/y wire from the (cntr) drop assembly you have eliminated the 3 switches on the cntr drop assembly. If this makes the offending sound go away, you have isolated your problem to one of the 3 switches on the drop assembly. So, hook the w/y wire back up and remove one of the wires from one of the switches on the drop assembly. Say remove the white/orange wire from the right target on the cntr drop. If the sound still persists reconnect w/o wire and remove the brn wire on the left target.
You will need to do this for each wire on the w/y circuit until you cut the wire that makes the offending sound go away.
12) If none of the above works out, then you will need to disconnect that huge connector in the 8-place drop assembly and see if the offending sound is living in that drop assembly. Disconnect it and credit another game.
REMEMBER: ALL 3 balls have to loaded to credit a game.
I hope all of this helps you out.
Good approach @cottonm4. Taking it one step further... Instead of cutting row return lines once finding out the offending column, you similarly can pull J2 I0-I7 pins one at a time to get the right row. So, column and row will give you the answer.
Reno, NV
