It makes the switches repeat.

Ask me how I know this!

Williams didn't really have a need for that since they scan their switch matrix much faster than Bally does.

Also, there's concerns of whether the matrix is strobed active high or active low, sometimes caps just won't work at all.

A cap isn't going to do anything with non-momentary targets in any case. On ballys they're only meant to make very short closures last longer so the MPU can read them.

How have you cleaned the contacts? There are some chemicals you can try if all else fails that can do wonders. Have you confirmed it's the contacts that are the issue by jumpering the lugs?

You're thinking from a hardware perspective. The switches that are closed always show 'closed' in system 7 to the software, it just depends on how much time the switch would be 'open' to see if it gets repeated.

In my case, I stuck the switch cap on the extra ball trigger switch because it was missing as the ball rocketed by it. It made it with the cap on there, then it repeated it over and over until I turned the machine off.

Do this. Adding a switch cap to fix a hardware issue seems like chasing your tail.

What kind of driver board do you have in your game?
Are the switch matrix resistors still in place or replaced by jumpers?
https://www.pinwiki.com/wiki/index.php?title=Williams_System_3_-_7#Wire_Jumpers_on_System_7_Driver_Boards

I'm having a similar problem with my sys7 Barracora on some roller over switches. If I roll a ball over them slowly they register. If a ball goes though too fast it won't register. I thought I had cleaned the switches really good. I cleaned them a couple times with lacquer thinner and Q tip followed by alcohol and then swiped a business card though them. Still had intermittent problems.

I decided to remove the switch and clean the contacts with Novus 2 and was surprised to see how dirty my white paper towel got. That switch seems to be much more responsive now so I am going to do the rest of them tonight.

Inspect the switch contacts - if the gold plating is gone (even if you see just a dot that's missing, right where the other contact hits it) it needs to be replaced.

Some people (myself included) use DeOxIt on these situations, and while it does work, the contacts should really be replaced instead.

DeOxIt works great on the system 3-6 drop target boards though, that's what I originally got it for.

Do you have issues with any other switches? Maybe your connectors in the head are suspect. Switches go through those multiple connectors, I don't care for those myself, I like less connections to go bad vs. more.

They really shouldn't tarnish too quickly once clean if the plating is there.

#frenchmarky, curious how you went with this, i have a hyperball thats a bit touchy on the microswitches on the tubes,i did change one bad one , fast balls fail to register , slow do, i was thinking caps too , or maybe better a 1n4148 instead of the 1n4004? , i have also done the 4049 and 7406 's plus the 16 x 470pf caps.

Changing the diodes to the smaller glass type will have zero effect. Yes, the 1N914/1N4148 types are faster acting but we are talking megahertz not the slow switching here.

so probably the idea is to slow the ball down in the tube to pass by the switch at a certain rate, when they write the code for the eproms they have a number of scan cycles on the switch port >x <y sort of thing, to be needed to be detected to make it a valid switch input i thought, this would be how they eliminate spikes being transformed from other circuits in the parallel wires in the harness like a transformer of sorts. might try the cap idea like a bally just for a giggle, sometimes fault finding can be eliminating things , especially when its confusing

likely this won't work, as noted previously. It will repeat once activated. Now, that's with the particular cap value that bally uses, so maybe a different cap value will work here.

There's a much easier way to lengthen a switch pulse on a microswitch - instead of the activation point being an inverted V (--^--) you can reform the wireform to be flatter at the top ---\___/ (flip that diagram) - so the ball will physically roll with it activated for a longer time. I had to do this when I swapped an AFM playfield to get the saucer shot consistently registering.

The software switch smoothing in system 7 counts the amount of time a switch is physically closed depending on the type of switch (there are 7 standard types, but the timing is different from game to game).

77 days later and i finally got round to playing with the tube switches with a clear head. i had replaced the micro and the diode to see a slow switch actuation was registering but a fast one like the cannon would deliver wouldn't. i tried a 473 polyester and it was not any help. i tried a 105 ceramic and bingo! things are happy. next is to try the other six or so, or maybe ill load the whole lot up? i hadn't read the comment about switch blade shaping, makes sense but maybe will also send me silly trying to get it right for each unit. it is kind of like the switch 330ohm verses wire link jumpers between -6 to -7 games maybe. crossing fingers multiple caps wont have some unwanted side effect.

20231115_230703 (resized).jpg

and it seems to work, i did have trouble getting the balls stuck thru poor bending of the actuator,
quite frustrating. when the balls go in the tubes and "vibrate" their way down the switch was always guaranteed to register
when it seemed to thunder thru it could sometimes not register.