Well, after restoring 5 to 6 Classic Bally Pinball machines and applying the same electrical modifications to the Solenoid Drivers and Regulators board, I have decided to tackle the implementation of a new board devoid of the original flaws of AS-2518-16 and -22. It is just incredible to see that Bally kept some of their mistakes from 1977 into 1983, revisiting the board only once or twice and still not fixing the problems.

I wanted to create something that would be still faithful to the original AS-2518 SD and Regulators board, while bringing a few features to help debug a machine. Once the whole pinball machine works, you never think about individual boards. Just remember what you would have given to pinpoint and locate certain issues, while rebuilding and restoring your favorite machine. I also wanted to design something superior or at least more interesting and faithful, than the existing current commercial solutions for that board.

This new board offers the following:

- Improved 5 VDC regulating stage protected from short circuit and temperature overruns.
- Immediate visualization of the low voltages (13.5 VDC and 5.0 VDC).
- Improved PI filtering with considerable electrical capacity.
- Limited heat dissipation.
- Modern components.
- Still fully compatible with the old and original components (for nostalgia)

- Improved High voltage filtering stage.
- High temperature capacitors (105 C) and hardened components.
- Immediate visualization of the High voltages (240 VDC and 170 VDC)
- Protected fuse and visualization of blown fuse.

- Enormous ground plane, linking all grounds together (5VDC, 43VDC, 240VDC).
- Complete and switchable isolation of the Regulators and Solenoid Drivers sections.
- Visualization of the coil firings (display is also switchable).
- Permanent (switchable) enabling of the Flipper relay for fine tuning and adjustment of the Flipper contacts.
- 12 VDC Computer Fan connection to keep your backbox fresh and cool and your precious boards healthy.
- Use of new and available components for the most part.
- No usage of patented and proprietary FPGAs.
- Through-hole technology for easy rework by the regular amateur, not owning Surface Mount de/soldering equipment.
- Gold plated 0.100 connectors for long term reliability with increased pins length.

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The board is made of 2 mm thick epoxy and is very stiff and solid, unlike the original Bally 1.4 mm boards made of cheap epoxy or Bakelite. The markings are very complete to help the restorer to understand and figure out what is going on, without resorting to the manuals at all times:

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The board that you see on the pictures is built specifically for my Playboy Bally pinball. Playboy uses a very limited set of coils and as such, I did not solder all the components usually found on a fully populated board. Why waste precious components? I have built multiple boards and this early version (below) is fully wired with 19 drivers:

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Let's take a close look at the 5VDC regulator stage:
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This board is designed to accommodate the original components and the now defunct 78H05K TO-3 regulator. Not that you would ever do that, but for the nostalgics, insertion of the old components would work fine. The dangling and tiny wires of the original capacitor have been replaced with snap-in capacitors providing 3 times the original electric energy. Two LEDs immediately inform you of the 13.5 VDC (RED) and 5.0 VDC (GREEN) voltage presence. If after installing your board, the green LED is not ON, it is most likely that you have a short circuit on the 5 VDC circuit.

The High Voltage regulator:
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This section is pretty much identical to the original and very well designed regulator, by Bally. Components have been improved and rated higher than what they came with the original Bally boards. Improved filtering with high-temperature capacitors (these babies do heat a lot with the high voltage) and immediate visualization of the 240 VDC (RED LED) and regulated down to 190 VDC (GREEN LED). Adjustment is possible and I usually run my displays at 160 VDC for long term life. The fuse is a 5x20 mm type and is fully encapsulated into a protective plastic case. Yes, being careful, you can replace the fuse without shutting the machine down....at your own risks.

An additional YELLOW LED indicates the presence of the 43 VDC for the Flipper Relay.

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The Flipper Relay is similar to the original Relay used by Bally, relays of excellent manufacture and high reliability (OMRON). A sliding switch allows you to enable the relay permanently (ON to adjust the flipper contacts or anything else) or in AUTO mode, that is to say controlled by the pinball CPU.

Connectors are gold plated on all 0.100 connectors with increased pins length (+1 mm) for additional and more reliable contacts:
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The Solenoid Drivers section is improved by RED LEDs displaying the action of the coils, in real time. The impulse are for the most part way too short to be clearly visible, but in static mode (or test mode), the LEDs will give you a confirmation that your coil and associated thyristor are working.
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Here again, the display section can be switched off as well as the entire Solenoid Driver section, using two switches:
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For instance, you can "disable" the Solenoid Driver section, "enable" the LED display section and using a piece of wire connected to the ground, touch each Thryristor metallic part and verify that each coil works perfectly. In normal mode, you would enable the Solenoid Driver section and turn off the Display section.
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It is interesting while playing a game to watch how the various coils are addressed. I have to say that sometimes, I am not sure what the Bally engineers had in mind when draining a ball for instance.

Finally, something which is missing in these machines and so necessary: a FAN !! This board offer a native and standard 12 VDC connection for a 120 mm computer fan. I am using a 120 mm fan rated at 19.5 dB, pretty much inaudible.

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Here is the board in its new habitat:

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and on the machine:

I hope you have enjoyed this crazy project, which will offer me a lot more reliability and diagnostics capabilities on my Classic Bally machines. If I find the time, I will try to post a video showing a play on a Mata Hari machine. The use of the four chimes for scoring, is particularly interesting to display.

I am not planning to offer this board commercially or compete with any of the current players in this arena. I just wanted to build something I can trust and that will allow my machines to live for another 40-50 years. However, if you have a serious interest for that solution or are curious to own one for bring-up purposes, you can always send me a Personal Message on the forum. I will be happy to assemble one for you.
Yves

I do not doubt that a lot of people have the skills to assemble a printed circuit board. The difficulty is finding the right parts and putting them together and making sure that the finished product works correctly.

I do not aim to be an "Heathkit" look alike and cannot afford to write an extensive documentation and bill of materials for just one or two customers. So, if there is a specific interest, I will provide complete and fully assembled boards with their fan unit.

Yves

Arcademojo, what an incredible collection. Congratulations.

Yves

Yes, I will as soon as I win the lottery!

Yves

Yes GPE, I thought about that but actually found that the 74LS154 can still be had for a few dollars.
But I agree with you, a pair of 74138 makes a lot more sense.

Yves

Okay, it is time to pull out the soldering iron and the solder paste:
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Yves

I just finished a new board for my Mata Hari. I also installed the fan that will provide a nice breeze through the back box.
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For this usage and since Mata Hari uses pretty much all the coils available with its Chime unit, I assembled a full board:
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It works very well and I am happy to replace the old (although refurbished) and original Solenoid Driver board that came with the machine.

Yves

Here is a crude video of the New Solenoid Driver board working during a simple game, from Power up all the way to the end of the play. I do not have a fancy camera and will try to post something better in the future. This is just to give you an idea of what this board does. Keep in mind that the impulses on the coils are very short, but Mata Hari with its Chime unit is somewhat unique and offers more activity than a regular pinball machine with a sound card:

Yves

A few more pictures of the board recently finished and sitting in Mata-Hari:
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Close-up on the Relay and its switch:
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The two switches allowing the disconnection of all temporary solenoids and visualization of the coils firing:
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Close-up on the High-Voltage section, with its over-sized components, fuse receptacle and monitoring LEDs:
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The coil modules, completely independent of each other:
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Yves

Ken,

I thought about this, but discarded the idea, due to cost, vibrations and reliability of the relay. How many times have I had to change a relay over the course of 16 years I have played with Bally machines? Never!

If it fails, the relay can be replaced relatively easily by sucking out the solder and installing a new one.

Thank you for the suggestions, though.

Yves