Inkochnito's Bridge Board

Some time ago I heard about the design problem in a large number of Williams games. The problem is about missing the fuses in the 18V (controlled lamps) and 34V (solenoids) circuits before the bridge rectifiers. Because of the missing fuses things can go very wrong with these games. When a short occurs in a bridge rectifier there is a possibility of burning wires from the transformer to the bridge rectifiers. In worst case scenario even the transformer goes up in smoke. In the best case the main fuse blows and turns the machine off. Look at the bottom of the page for a few examples of how things can go wrong.

To remedy this problem simply placing fuses in the circuit before the bridge rectifiers is advised. A very doable solution. Another problem could be the very large capacitor in the 18V circuit.  The life expectancy of 10 to 15 years is already long past for all machines. Now isnít that much of a problem for the controlled lamps, but the electronics might object. When your controlled lamps burn less bright there might also be a problem with the bridge rectifier. All these problems can be fixed by using my brand new Bridge Board.



On this board are the bridge rectifiers, capacitor replacements and the new added fuses. These components can continue to serve you for another 10 to 15 years and are easily available.  Simple screw connections, no soldering skills needed. The bridge rectifiers are on the back side of the board and are also used for mounting the board in the back box. This way the bridge rectifiers have the best cooling thru the metal back plate in the back box of the machine. If you want you can also mount the bridge rectifiers on the front of the board, but an extra cooling body is advised and the use of mounting spacers. Additionally this new board also has 2 leds for checking if the exit power is present.

You can use this board in ALL games from Williams System 3 up to System 11A. Data East used a lot of technology from Williams. So you can also use this new Bridge Board for Data East games as well. Even the first 4 games from Sega too.
Complete list of supported games

I do have to mention that Williams solved this fuse problem from System 11B. From this series Williams used an Aux. Power board which has the fuses added. Data East solved this missing fuse problem from their 3rd game (Time Machine).

Despite of the solved problem in Data East games, you can still use the new Bridge Board to replace the large expensive capacitor. The big advantage is that you also replace the old bridge rectifiers and the fuse holders all with one new board. However in some Data East games a motor is used. This motor runs on the 26Vac power taken from the bridge rectifier for the coils (white-red wires). Usually these extra two wires are connected to a 2-pin connector. When you remove the unneeded fuses for the bridge rectifiers, this motor will be left unfused. I recommend to reuse one fuse holder for the motor connector. Use a 2.5 Amp. fuse for the motor. It depends a bit on the type of motor used. More information is in the PDF file.

If you have any questions about this board or its connections, please send e-mail  me at or
Here is a link to the pdf file in which the schematic and all connections are explained.
Inkochnito's Bridge Board (PDF in English)

Inkochnito's Bridge Board (PDF in Deutsch)
Inkochnito's Brug Bord (PDF in Nederlands)

Here are step by step instructions for connecting the Bridge Board in a Williams game like Fire Power.

Here are step by step instructions for connecting the Bridge Board in a Williams game like Laser Cue.

Here are step by step instructions for connecting the Bridge Board in a Data East game like Checkpoint.

© 2018 Inkochnito
Designed in coŲperation with

Here are images of the prototype board installed in my F-14 Tomcat.

This is a Black Knight (early production)

This is Gorgar (with a Rottendog power supply)

This is from a Fire Power

Here are some images from games in which you can place the Bridge Board.
The components in the red circle are the parts which will have to be removed and replaced by the new Bridge Board.


                                                                                                                                Data East - Guns n' Roses

                    Data East - Torpedo Alley                                                                        Sega - Maverick

Notice that Maverick has two large blue capacitors. With Sega games you have got to pay extra attention, because these games have an extra capacitor, bridge rectifier and fuse for the large dot matrix display power supply. If you like you can also replace these with a second Bridge Board and use only the 14V connection.

Here are a few images of how things can go wrong....