Leon Borre WMS 6 Digit DIY LED Displays
Williams led display's for models 3,4 and 6.
* * * * * * 6 digits. * * * * *
Williams uses one board to steer all the display's . On this board is mounted the display for the 'credits' and ' ball in play ' indication, the players displays are connected to this board with cables. For that reason by a conversion to led display's we have to change all display's at the same time as they all are steered by the same board. Luckely there are only 6 IC's to change and the new IC's fits perfectly into the emplacements of the olde ones! Furthermore we have to adapts the runs that feed these IC's and 16 resistors to change . In reallity a simple job!!
The display driver board. There are different models this article handels the 6 digits board using IC's ( UDN7180 and UDN6184) to steer the display's not transistors! Take care of the orientation of IC4 a UDN6184 he is orientated the other way around , compared to all the other chips !!
Here the driverboard with the six IC's that have to be replaced removed. The yellow arrows indicates where the 7180 where the blue arrow where three 6184 's where and the red where, the fourth 6184 was ( IC4) the one orientated the other way around!
Let's take a look at the schematic what we have to change, the complete schematic is here ...... 
We have to change the resistors R1 to R14 from the original 10k into 33ohm resistors, of course change the both UDN7180 by a ULN2803 and remove the tension of 100 volts cominig to pin 10.
On the right of this picture and just above the display we find the four UDN6184, these have to be replaced by UDN2981 ( = TD62783) Here to we have to adapt the tensions coming on pins 9 and 10. The new UDN2981 (TD62783) needs ground on pin 10 and 5 volts at pin 9.
Practical realisation.
Remove the 6 Ic's 4x UDN6184 and 2x UDN7180, solder at these places IC sockets and replace the two 7180 by a ULN2803, and the four 6184 by UDN2981 ( = TD62783) .
Here the board with the six IC sockets soldered in.
Remove the resistors R1 to R14 and replace them by 33 ohm resistors ( 1/2 watt types) yellow arrow
Adaption of the tensions.
The adaption of the two ULN2803, simple, just one run to cut. On connector J7 pin 6 ( solder side of the print ) starts the run bringing the 100 volt to this IC's just cut the run there , that's all.
The red arrow indicates where the cut is made. ( pin 6 of J7 )
The tension adaptions to the four UDN2981 ( TD62783) is a bit more complex. We start with pin 9 of these four IC's. The three UDN2981's in the middel of the board on one line have their pin 9 connected together with one run , Cut this run , it's the middel run from three coming from under the IC. We cut this run about 1cm left of the middel IC. The last UDN2981 his pin 9 is soldered in the middle of a large solder-island and it is hopeless to cut that loose, so i decided to bent the pin 9 of that one upwards and to solder a fine wire directly on the pin... Over to pin 10 , luckely all four pin's 10 are connected with one run and come together at pin 2 of connector J7. All we have to do to separate these pin 10's is to cut the run from J7 pin 2 that way the 4 pins are together and isolated. Cut the run just afther the arrival at pin 2 of J7.
The cutted run is the middel one coming from under the middel IC.
Now we bring the tensions to the jointed pins of these four IC's. Pin 9 requires 5 volts . The wire starting from the upwards bended pin 9 of IC4 comes to the cutted run left from the middel IC. We solder it to the right side of the cutted run closes to the middel IC. From there we connect the run at 5 volts wich we find on C1 right side see photo.
Starting at the red arrow ( upwards bended pin 9 ) to the right side of the cutted run ( middle yellow arrow) to 5 volt ( right side C1) Or you can use a separated power source , this is even better and give the possibility to ch ange and adapt the brightness of the display's.. ( See at the bottom of the article )
Pin 10 goes to ground. Solder a jumper between the run that has been cutted free from pin2 J7 and the nearby ground island. This concludes the tension adaptions.
The arrow indicates where the run was cut and the black jumper brings now ground to the run.
The new LED display's and how to connect them.
The adaption of the driver board is not to complicated, but now we need complete new boards for the display's. We have to make a printed circuit for that of the same size and with the same edge connector. As long as these are not commercially available it will be difficult to the average pinball fan to make these. Myself i have what it takes to make pcb's but not on a commercial base and not to many.
Anyway here the design like i made them.
The design of the print.
This print is suited for 20mm large display's. I use the HDSP-3400.There are several jumpers on the board because i had to follow the same signal alignement of the excisting edge connector.
The finished home-made print.
Finished display.
For the players , we just have to solder the display's and the jumpers on the print and put on the connector.
There are 10 jumpers ( red on design).
The print is designed in a way that when i cut of the lower part i can use the print in the middle of the master display board where it replaces the glass display that gives us the credit and " ball in play" indication.
Cutted print
There are still soldering islands for every connection.
Cutted along the red line here the positions of the solder - islands for the seven segments a,b,c,d.. and the 6 digits.
The cutted display mounted on the master display board
How to connect the credits/ball display?
We connect in the excisting holes where the glass display was. These holes are numbered, from 2 to 40 . Attention 2 to 17 then a gap ( no holes) and it continues at 25 to 40. First the segments a = 2, b = 4, c = 6, d = 34,e = 36, f = 38, g = 40. The digits, units at hole 3/5, tens = hole 9/13 , hunderds = not used, thousends = 25/27, ten thousends = 31/33", hunderdthousends = not used.
A complete and working players display on the William test-bench during classic display test, and also the credit / ball in play display in the middle of the master display board .
Final remarks.
The added display's will take more current from the 5 volts supplie. An average Williams pinball machine of this type draws about 2amps. from the 5 volts. It's better to change the excisting LM323 5 volt regulator , who can take a max. of 3 amps by an 78H05KC regulator that can handle 5 amps. Just remove the old LM323 and put in the 78H05KC.
The red arrows indicates the LM323 to change with a 78H05KC , the yellow arrows shows the high voltage fuse , he can be removed as we no longer need that high tension.
A second solution is to use a separated 5 volt source to light the display's. Use a simple power block that can be setted between 5 up to 12 or 15 volts. 1 amp ( or 1000mA), The negative comes to ground and the to the red wire that normally was connected at the right side of C1 on the driver board. Changing the output tension from 5 to 9 or to 12 volts will increase the brightness of the display's , choose the one you like best.
A simple and cheap power source, you can choose an output voltage between 1,5 and 12 volts.
Higher brightness of the display's at 12 volts.