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I’ve written a couple of EM tables and I’ve incorporated code in them to drive chime units in anticipation of building or buying a chime unit to put into my machine. Being fairly frugal, I didn’t want to drop big bucks on a unit so my first thought was to see if I could make one from scratch.
I did a bit of research into how how chime bars work, bought a cheap Chinese spring retracting 12v solenoid and made a test bed to see if this was a viable option. I needed a resonator box to amplify the sound so I chose a cheap single gang electrical box and cut a section of aluminum bar stock as the chime bar.
According to my research, the holes for the supports for the chime bar should be located at a nodal point on the chime bar. A node is a point on a bar/string that doesn’t move when the bar/string vibrates. Vibrating bars/stings vibrate on their whole length, half length, quarter length etc and each of these vibrations creates a different overtones that give the bar/sting its distinctive sound. It turns out that locating the holes 22% of the length of the bar in from the ends is the right location so I cut the bar to make this work on my test bed.
Here is a video of the unit in action.
The sound on this video is poor because it was shot with my phone but it shows proof that the concept works, it just doesn’t have the sound that I was looking for so I moved on…
I then watched eBay for a decent deal on a Gottlieb chime unit. I went with Gottlieb because the general buzz on the pinball sites is that they made the best chime units. I also looked into buying coils, plungers and hardware but both of these options were fairly spendy.
I then found this beat up “parts only” Gottlieb chime unit on eBay for $14.
The coils supposedly worked, it is missing a support bolt for the chime bars and the resonator box looks melted just under the missing bolt, a real gem…
When the unit arrived I checked out the coils and all of them read 12 ohms which is a great sign that there were no dead shorts in them. Two of the coils were missing most of their paper coverings and one looked like an after market replacement since it had a green wrapper rather than white like the other two.
I called Pinball Supply in New York because they had a Gottlieb chime unite rebuild set. The guy that I talked with on the phone was super helpful. He said that my unit was from the late 60’s to early 70’s because of the coil numbers and the gold finish on the unit. He confirmed my suspicion that cycling time for these chime units might be a problem with virtual machines and that Bally had a partial solution to that issue. More on that later.
I wire brushed up the unit and took off the pitted copper plating so the whole unit was brushed metal. I would have liked to save the copper color but there were burn marks where one of the coils went up in flames at some point in the past and the unit was badly pitted/rusted in many areas.
I looked online for Gottlieb chime bar dimensions and found plans with dimensions for them. They are made from 6160 alloy Aluminum bar stock that is 1 1/2” wide and 1/8” thick. The 6061 is a special allow that is stronger than what was available at my local big box stores so I had to order some. The bars turned out to be tuned to a C minor chord (low to high C, Eb, G) which is kind of cool to think that Gottlieb went through the trouble of designing their unit around a chord. The fact that the cord is minor fits perfectly with my pinball skills since most of my games don’t have a happy ending to them (minor musical joke, pun intended).
I repaired the melted resonator by placing a splint inside the resonator and then poured epoxy tinted with a special black dye so the repair was well hidden. I also bored a hole for the missing chime bar mounting bolt, tapped the hole and made a replacement. Lastly I made new paper sleeves for the coils that were missing theirs so the unit would look spiffy.
When the parts came from Pinball Resource I finally put the whole thing together and tested it out. The unit worked great but one of the coils couldn’t keep up with the other two in terms of speed so I tried Bally’s solution. It turns out that the magnetic field of a coil only interacts with the outer layers of the plunger so Bally made hollow plungers to reduce their weight and make them accelerate faster when the coils fire, I counter bored one plunger to 9/64” with a depth that just reached the nylon tip. This reduced the plunger weight by over 30% and fixed the problem coil’s cycling issue. I then bored out the other two and made a test table to check out the cycling speed of the coil units.
Here is a link to the test table if you want to try this out on your unit.
https://drive.google.com/file/d/1b6aEHtkQlAxwDa0_FsyOKu3Hg2jmIBjF/view?usp=sharing
The table works by cycling the coils five times at different timer intervals. In this video you can see each chime bar cycled at 200ms, 150ms, 125ms and 100ms.
As you can see each of the coils can keep up at 200ms and 150ms but they can’t quite cycle fast enough at 125ms and they don’t even come close at 100ms. I tried 140ms and two of the coils could keep up but one hit only 3/5 times so it looks like 150ms is top speed for my unit.
I then needed a shoehorn to get the unit to fit into my Multiball Cab. The only open space was in the front of the cab on the right side. MJR tells me that Gottlieb used this spot on a lot of their machines but that was just a happy coincidence on my part. Here are photos of the unit in place.
I use MJR’s Pinscape boards in my cab so I made a special Chime board to drive the unit. One of the things that I really like about MJR’s design is that he put 555 timer circuits on each of the chime board outputs so that if the circuit is left on for more than 1 1/2 seconds, the timer automatically opens the circuit as a means of protecting the coils from overheating. Remember each coil only has 12 ohms of resistance separating them from being a dead short so they will get toasty if left on for an extended period of time.
I have to say that the chime unit is one of my favorite toys in the cab. It really adds a lot to the EM tables both in terms of sound as well as feel since you can tactilely feel the coils firing. If you’ve got the space and like EM tables, a chime unit is a great addition to your cab!
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Ah oh… randr is going to have a meltdown!
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I just figured out how to get the videos into the post so they are now up in the first post.
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Very cool.
I installed my chime unit last night and I’m absolutely thrilled with it!
Current Project: Perpetual updates of VPX physics.
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I bought two working Gottlieb chime units four years ago in anticipation of putting them in my cab, one for $58 and the other for $75. And there they sit in my office. One of these days…
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Nice! I had my chime unit a year before I installed it! But it’s the coolest thing when playing these classsic tables does not get any more real then with real chimes.
great write up!
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I bought two working Gottlieb chime units four years ago in anticipation of putting them in my cab, one for $58 and the other for $75. And there they sit in my office. One of these days…
I highly recommend them. They are a game changer for me. Brings EM’s to life. I pinball isn’t a pinball without chimes!
Current Project: Perpetual updates of VPX physics.
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I ran the chime test table with my chimes, two bars got 100ms and one gets 150ms.
Current Project: Perpetual updates of VPX physics.
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What manufacturer made your chime unit? You should crank the timer speed up and see if you can get better than 100ms with your turbo charged unit! The guy from Pinball Resource said that cycle times were a problem with many chime units in the later years of EM machines. He said that bonus multipliers were the main cause of problems for these units.
Hey CarnyPriest you should check out the cost of chime units these days on eBay, you could turn a profit on one of those and use the money to put another nice toy under the tree for your cab this Christmas.
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My chime unit is out of a Williams Fan Tas Tic.
Current Project: Perpetual updates of VPX physics.
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I love this post so much. Anyone with DOF and no chimes is missing out big time. Screw all the flashing lights. This is the best.
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Rothbauerw how many volts are you putting through the coils? From what I’ve read in one online post about chime units Gottlieb 24v, Williams 24v, Bally 50v. These coils should accept higher voltages and with the higher voltage a stronger magnetic field and that could make a big difference in performance. A few extra volts might change some of those near misses at 125ms to hits in the video that I posted. Just a thought…
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24V and yes, I think voltage will make a difference for speed and volume.
@ranr, did you ever try that Evel Knievel unit at 48V?
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Yes I did but not with the test table. I should hook that back up and test it
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Well I did an experiment this morning with voltages. My thought was that increasing the voltage would increase the magnetic field strength and that might improve performance by helping the coils cycle faster.
I hooked up a voltage booster and fed it 24v 15A max current draw used this to put out 35.6v to power the chime unit. I used the chime test table and the results showed no improvement in cycle times, in fact I think the chime unit actually performed slightly worse with the higher voltages. This pretty much convinces me that the limiting factor for chime speed is gravity, friction and geometry.
If the tone bars were lowered or the coils were raised so that the plunger retracted further into the coil upon strikes, I think that would improve performance. I also think that adding return springs to the plungers to get them further into the core of the coils would help dramatically improve performance. In my Mark I test bed I could cycle the chime bar much faster with the 12v solenoids wit return springs than the Gottlieb unit that uses gravity and elastic collision to return the plunger.
Another option that I’m not sure how to implement without causing a dead short would be to put reverse polarity on the coil after firing and use that to draw the plunger into the coil prior to the next positive voltage spike. It might also be that the EMF spike diodes are preventing the magnetic field dispersion and that could be adversely effecting performance.
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I have coils that aRe 48v so maybe they will be better but they don’t have the nice deep chime of the older units. I’ll rig up a test for this and see
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This whole chime thing has me working on a “test table” that plays yankee doodle! no joke
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Looks fantastic. I just picked up an EM myself and found a Gottlieb chime unit to put in it as it was missing one. Was toying with the idea of finding one for the virtual cab before this. This thread is great. I could get another williams or a gottlieb chime unit (couple for sale here in Australia but rare) and try to wire it up. I don’t have spare triggers on my current solenoid driver board though for DOF at the moment and would be worried about running the coils at lower voltages than intended. Maybe i could rig them to a teensy output? Plenty of spares on that.
Thoughts?
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I really like the idea of having multiple units for different machine manufactures. I personally don’t have the room in my cab at this time because my massive subwoofer has 1 1/2 cubic feet of the cab tied up with its enclosure. If you run the chime coils on lower voltage then spec then the coils won’t fire as strongly as designed and may not fire even hit the tone bars.
I don’t think that the controller matters so long as what it controls can can sink about 2 amps to ground (12 ohm coil at 24v = 2 amps). I use MJR’s Pinscape board so I have far more slots for toys than I could ever use. His chime board also has 555 timers built in to prevent a coil from being left on for more than a second or so. I strongly recommend Pinscape but I know most guys already have another system in place and it would be a pain to switch over…
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