Before I stripped and cleaned the playfield on my last action hero, I had a phantom ball drain occur a few of times. When I say phantom drain I mean the flippers go dead, end of ball music plays, you are awarded a bonus and then the next ball is served up. I suspected at the time it could be a trough switch needing adjustment and since I was going to look at the ball trough as part of the playfield cleaning, I didn’t bother looking closer at it. Fast forward to post cleaning. I had the playfield back together and began to test. After a couple of games I noticed that the phantom ball drain was now far more common – in almost every game it would occur. I also began to notice other side effects where some playfield features would be activated without hitting the corresponding switch.
After some additional testing during a game, I found a direct relation between the phantom drain and the “R” drop target. When this target was hit, it would instantly believe the ball had drained, award a bonus and continue to the next ball.
Now that I had a suspect switch, I went into switch test mode and explored the switches to see what I could find. This is the switch matrix from the LAH manual:
I went through all switches, making note of the ones that triggered two switches. When a switch in row 6 is pressed, it’s corresponding switch in the same column on row 2 is pressed also. For example:
Pressing “Left Coin” (#6) will activate switches #6 AND #2 (“4th coin”).
Pressing “Left Lock Top” (#22) will activate switches #22 and #18 (“Drop Target R”)
Pressing “Left Ramp Enter (#46) will activate switches #46 and #42 (“Right Return”)
and so on – each of the 8 switches on row 6 will activate both it and the switch in the same column on row 2.
At this point I had some consistency, but needed to understand better what was actually happening. After doing some research today (I’ve included a few of the links below for future reference) I got back into it to. At first tonight, the issue was not present. After a couple of games, the problem came back. I lifted the playfield and entered switch test mode to physically observe the switches on row 6 when activated. The problem stopped again.
I was feeling a bit more positive at this point – since the issue would go away for a bit when the playfield was lifted, I was confident the issue would be a switch wire or diode shorting – touching something it shouldn’t. Although maybe harder to track down, easier and less invasive to fix that CPU board issues.
After some further diagnosing of the 8 switches on row 6, I found the problem went away when I disconnected the drop target bank. When I connected it back up again, the problem returned. I repeated this a few times and the behavior was consistent. The issue was with the drop target bank.
There are 5 switches, one per drop target. There are also 2 extra switches, which are connected to a bar sitting behind the targets (hitting this during play will reset the target bank). This is where the problem was. Tucked away under one of the bar switches switches, there was a blue / white wire not connected to anything, but was lightly touching the switch lugs for the “R” target. At first it looked like it should be there, until I moved it and noticed that it was completely loose. I missed this the previous night as it was well hidden behind the rest of the wires.
Looking at the switch matrix, I could confirm the blue/white wire should be connected to the mircoswitch above it – for the drop target bar – it should not be touching any of the drop target switches.
This is an interesting one as the drop target bar has two miscroswitches. Activating either will activate the switch. This is why it was not immediately obvious. The switch still worked when pressed as the other microswitch was still connected. But the wire running to the second switch had come away from its solder join and started touching the “R” target. This also explains why the problem went away some times as it was only just touching and some slight movement one the wire would move it away.
In the photo the purple square it around the blue wires – they should be connected to the lug where the green arrow is pointing. Instead they are lightly touching the lug of the R drop target where the red arrow is.
The wire was soldered back onto the mircoswitch and my switch matrix problems have been solved. It seems that this wire had been coming loose before I started the playfield cleaning, but given I had the playfield up and down several times during the process and threaded wires up through a hole close to the drop target bank for the tar pit, it was enough to move the wire close enough to the R target to make the issue occur regularly.
For future readers, some useful links I came across while researching the switch matrix and similar issues: