Hi everyone,

I have a 1980 Black Knight and the feature lights have been intermittent for the past six months. Sometimes they work and sometimes they don't. There doesn't seem to be a rhyme or reason or scenario when they work vs don't work. All GI lights work normal. I have checked the obvious and I think there is something on the driver board that is causing the issue. One thing to note is that when powering the pin up the feature lights will flash briefly and then turn off. The same flash happens when turning the pin off.

- I checked all fuses - They are good
- I re-seated all connectors on the power board, mpu and driver boards
- I have 18v coming out of the driver board and traced the 18v all the way down to the lights,

So I think it is not grounding the lights properly???? Perhaps the transistors????

Any thoughts or additional troubleshooting steps I should follow?

Thanks in advance.

-Steve

Sorry, forgot to mention that was one of the first things I did last year.

I was just playing it again and the feature lights came on, some of them, but not all, and some were much weaker in illumination than others. Then some faded. At one point in the game the Black Knight speaks and when he does the entire play field goes dark, including the GI. Once he finishes speaking the lights are supposed to come back on, however, none of the feature lights came back on.

I'll probably re-seat the mpu / driver boards again just to be safe and also take a look at all solder joints.

I also noticed that the TP4 only had .18 volts at one time and then later it had 4.19 volts.

Additional troubleshooting. The feature lights have 18v at them...... should it be 18? That seems high. If I manually ground a feature light, a few of the lights will turn on. I assume it is the entire row / column that is being grounded so they are turning on. Does this mean that there is an issue with the controller that controls the grounding? From my understanding the lights always have power, but they do not turn on until they are grounded.

Could a capacitor cause this type of issue? The reason I ask is that the way the lights are behaving lends me to believe it is not a bad connection, since they fade slowly or some stay on while others are off and then all of them work again. Or some other component that controls the grounding of the lights?

So I turned the pin on this morning and the feature lights worked for a while, but then suddenly quit again. I measured the voltage at j4, 5 and 7 and they were all right at 16v. I then measured the voltage at the feature light sockets and it varied from 3 to 14 volts (I assume since the lights are pulsed). I took video of when the lights turn off and posted the link below. In this instance they all shut off at the same time, during other instances they will fade or some will work and eventually shut off.

You can see the back box light and GI continue to work as expected.