(Topic ID: 216880)

Replacing Williams Drop Target Sliders with Reed Switches

By oldschoolbob

1 year ago

Topic Stats

  • 10 posts
  • 3 Pinsiders participating
  • Latest reply 9 months ago by HHaase
  • Topic is favorited by 7 Pinsiders


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#1 1 year ago

This may be difficult to explain. Last year I replaced the Horseshoe Slider Switches on my Disco Fever drop targets with reed switches. They worked very well – still working today. Now I want to do the same thing on my Blackout. The Disco Fever was easy because only the bottom contacts on the slider board were used. The CPU could figure out when all were down and reset. The Blackout has momentary contacts half way down and contacts on the bottom. (see first photo) switch 02 (resized).jpg

The bottom contacts are wired in series so when they all make contact the bank will reset. (see schematic)

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I have a few concerns with this arrangement. I’m not sure the reed switches are fast enough to register when the magnet passes by. On the other hand the magnet may be too strong and hold in the upper reed closed when it's in the down position.switch 04 (resized).jpg

One option would be to lower the upper switch to insure it registers but then it would be always closed when the target it down. The question is what would happen if switches 25, 26 or 27 were held closed? Would it keep scoring? Would it short something? Would it burn out a transistor or something?
switch 05 (resized).jpg

Looking at the Disco Fever diagram when the target is down the switch is closed. That doesn't seem to effect anything. Wouldn't the same thing happen on the Blackout?



#2 1 year ago


In about a week you'll be able to test it. Was just about to pack up a pair of boards for you.

To answer part of your question though, the 'falling' switch needs to be momentary. I forget the exact 'why', it's been a while. But something goes screwy in the way System 3-6 polls switches, I want to say it can only read one switch in a column, or maybe a row, at any given time. I'd have to look at some matrix charts to remember why.

It was a software thing, not a hardware thing. When Larry Demars came on board, he did a huge overhaul on the base software. This includes switch polling, among many other things, and is why System 7 and later machines went to single switches in their drop targets.

#3 1 year ago

The Disco Fever is a 1978 system 3 and Blackout is 1980 system 6. I'm hoping they both poll the switches the same way. If they do it shouldn't make a difference if the momentary switches are closed.

I'll experiment with some temporary jumpers - hope nothing burns out!


#4 1 year ago

The reason for the falling switch and bottom sitting switch was because the fall was a momentary scoring switch while the bottom switch was part of a sequence complete series of switches (that can't share a row or column.)

It's a carry over way of doing things from the EM era. If a temporary scoring switch is held closed, it could either bounce, OR, the same score value switch was used in multiple places and if one stayed closed, it would blind the game of all the others.

Later, they used the bottom switch (as a leaf switch) as both through software.

#5 1 year ago

I did some experiments today. I held down one of the top roll-overs - it scored as expected - one time. Then while holding it down I tripped all the other switches and they all scored as expected. Even the pop-bumpers and slingshots worked as usual. Then I held down one of the outlane roll-overs and tested again. Everything worked.

This tells me that the momentary switches on the drop targets CAN be in the lower position as shown in the last photo above and held closed until the target is reset. This will eliminate the concern about the reed switch being fast enough and the concern about the magnet strength holding the momentary switch closed when in the down position.

Next I was going to jumper the switches on the targets to be sure my theory was correct. So I pulled out the target assembly and that's when I felt sick. I noticed someone cut off one of the wires. I think I know where it connects but I ran out of time.

I'll have to continue my experiments later.


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#6 1 year ago

My theory was correct. Today I re-connected the wire (I think it just broke off). Then I turned on the game and jumpered the center target and left it connected (like a stuck-on switch). All the other switches scored as expected including the left and right targets. Then I jumpered the left target (while still having the center jumpered). Again everything scored as expected, including the remaining target.

This tells me the momentary switches can be held closed until they are reset when the bottom 3 switches are closed.

While waiting for Hans's boards to arrive I think I'll make a rough prototype to test the magnets and reed switch locations.


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2 months later
#7 1 year ago

I hadn’t forgotten about this thread. I was hoping to see Hans’ revised boards but I guess he is really busy.

I received his prototype boards a while back. They are really well thought out and well made. I made a few changes to the board and it worked great in my Blackout. I sent the information back to Hans. Let’s hope he’ll get them on the market soon.

Until then I’ll continue with my experiments. I still needed a second board for the Blackout plus a couple of boards for my new Flash. One of the things I learned from Hans’ boards was that the magnets are stronger on the edges than in the center. I had to offset the switches to one side to get them to work better. On my next attempt I offset the switches.

First Design:

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When I was almost done with that design I thought the switches may work better vertically. By mounting the switches vertically they were over the sides of the magnets.

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This design worked much better.

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This seemed to work much better and very little adjusting was needed to get it aligned with the magnets. I’ll admit my boards are rough and crude compared to Hans’ boards. But they prove the concept works.

Hans’ prototype:

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I can’t wait for these new boards to be released. With reed switches and magnets we’ll eliminate the need to adjust the horseshoe sliders. Dirt and dust won’t be a problem and there is nothing to wear out.

I now have three games with reed switches and magnets and they have been working great. I modified Disco Fever about 8 months and haven’t had a problem. I’m not an expert on reed switches but I’m willing to share anything I’ve learned if you’d like to try this modification.


#8 1 year ago

Yeah, busy is a bit of an understatement. and crap, I just got some fresh LED adapter boards and completely forgot to order the drop target boards.

I think there's 6 or 8 'almost ready to go' prototypes sitting on my bench for 2 months, untouched.

10 months later
#9 9 months ago

Another quick method might be to use your old PC board - clean it real good and solder on a couple of surface mounted reed switches. See photo.
Remove the horseshoe slider and epoxy on a magnet.

I haven't tried this yet but it looks like it might work.

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#10 9 months ago

Once I get done with the current crop of incoming boards, I think I'll take another look at this one.
Truth is, up until about two months ago I've been building stuff almost non-stop, hadn't had any time to do any development work.
Pretty close to totally burned out for a bit.

Starting to relax enough that I'm getting back into a development frame of mind.


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